Prospectus filed pursuant to Rule 424(b)(3)
of the Securities Act of 1933, as amended.
Registration number 333-188242

PROSPECTUS

$50,000,000
 
Active Power, Inc.
By this prospectus, Active Power may offer, from time to time:
 
 	●	Common stock	

 	●	Preferred stock	

 	●	Depositary Shares	

 	●	Warrants	
 	●	Debt securities	
 	●	Units	
 
Active Power, Inc. a Delaware corporation (“Active Power”) may offer and sell from time to time, in one or more series or issuances and on terms that Active Power will determine at the time of the offering, any combination of the securities described in this prospectus, up to an aggregate amount of $50,000,000.
 
We will provide specific terms of any offering in a supplement to this prospectus. Any prospectus supplement may also add, update, or change information contained in this prospectus. You should carefully read this prospectus and the applicable prospectus supplement as well as the documents incorporated or deemed to be incorporated by reference in this prospectus before you purchase any of the securities offered hereby.
 
These securities may be offered and sold in the same offering or in separate offerings; to or through underwriters, dealers, and agents; or directly to purchasers. The names of any underwriters, dealers, or agents involved in the sale of our securities, their compensation and any over-allotment options held by them will be described in the applicable prospectus supplement. For a more complete description of the plan of distribution of these securities, see the section entitled “Plan of Distribution” beginning on page 29 of this prospectus.
 
Our common stock is listed on the Nasdaq Capital Market under the symbol “ACPW.” We will provide information in any applicable prospectus supplement regarding any listing of securities other than shares of our common stock on any securities exchange.
 
As of May 31, 2013, the aggregate market value of our common equity held by non-affiliates was approximately $66.7 million based on the closing price of our common stock of $4.30 per share and the number of outstanding shares held by non-affiliates of 15,518,624. For purposes of the foregoing, the number of shares held by non-affiliates excludes all shares held by our executive officers and directors and any holder of 10% or more of our outstanding common equity. We have not offered and sold any securities in a primary offering pursuant to Instruction I.B.6 of the general instructions to Form S-3 during the period of 12 calendar months immediately prior to and including the date of this prospectus.

 
INVESTING IN OUR SECURITIES INVOLVES SIGNIFICANT RISKS. SEE “RISK FACTORS” BEGINNING ON PAGE 4 OF THIS PROSPECTUS AND IN THE APPLICABLE PROSPECTUS SUPPLEMENT BEFORE INVESTING IN ANY SECURITIES.

 
 NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE ADEQUACY OR ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

 

 
 
The date of this prospectus is June 26, 2013

 

 
Table of Contents

 	Page	
 	 	
Prospectus Summary	1	
Risk Factors	4	
Forward-Looking Statements	4	
Ratio of Earnings to Fixed Charges	5	
Use of Proceeds	5	
Description of Capital Stock	6	
Description of the Depositary Shares	10	
Description of the Warrants	13	
Description of the Debt Securities	16	
Description of the Units	28	
Plan of Distribution	29	
Legal Matters	32	
Experts	32	
Where You Can Find More Information	32	
Information Incorporated by Reference	33	

ABOUT THIS PROSPECTUS
 
This prospectus is part of a registration statement on Form S-3 that we filed with the United States Securities and Exchange Commission, or the SEC, using a “shelf” registration process.  Under this shelf process, we may, from time to time, sell any combination of the securities described in this prospectus in one or more offerings up to a total amount of $50,000,000.
 
This prospectus provides you with a general description of the securities we may offer.  Each time we sell securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering.  The prospectus supplement may also add to, update or change information contained in the prospectus and, accordingly, to the extent inconsistent, information in this prospectus is superseded by the information in the prospectus supplement.
 
The prospectus supplement to be attached to the front of this prospectus may describe, as applicable: the terms of the securities offered; the initial public offering price; the price paid for the securities; net proceeds; and the other specific terms related to the offering of the securities.
 
You should only rely on the information contained or incorporated by reference in this prospectus and any prospectus supplement or issuer free writing prospectus relating to a particular offering.  No person has been authorized to give any information or make any representations in connection with this offering other than those contained or incorporated by reference in this prospectus, any accompanying prospectus supplement and any related issuer free writing prospectus in connection with the offering described herein and therein, and, if given or made, such information or representations must not be relied upon as having been authorized by us.  Neither this prospectus nor any prospectus supplement nor any related issuer free writing prospectus shall constitute an offer to sell or a solicitation of an offer to buy offered securities in any jurisdiction in which it is unlawful for such person to make such an offering or solicitation.  This prospectus does not contain all of the information included in the registration statement.  For a more complete understanding of the offering of the securities, you should refer to the registration statement, including its exhibits.
 
You should read the entire prospectus and any prospectus supplement and any related issuer free writing prospectus, as well as the documents incorporated by reference into this prospectus or any prospectus supplement or any related issuer free writing prospectus, before making an investment decision.  Neither the delivery of this prospectus or any prospectus supplement or any issuer free writing prospectus nor any sale made hereunder shall under any circumstances imply that the information contained or incorporated by reference herein or in any prospectus supplement or issuer free writing prospectus is correct as of any date subsequent to the date hereof or of such prospectus supplement or issuer free writing prospectus, as applicable.  You should assume that the information appearing in this prospectus, any prospectus supplement or any document incorporated by reference is accurate only as of the date of the applicable documents, regardless of the time of delivery of this prospectus or any sale of securities. Our business, financial condition, results of operations and prospects may have changed since that date.

i

Table of Contents
 
Prospectus Summary
 
This summary description about us and our business highlights selected information contained elsewhere in this prospectus or incorporated in this prospectus by reference.  This summary does not contain all of the information you should consider before buying securities in this offering.  You should carefully read this entire prospectus and any applicable prospectus supplement, including each of the documents incorporated herein or therein by reference, before making an investment decision.  As used in this prospectus, “we,” “us,” “Active Power,” “the Company” and “our” refer to Active Power, Inc., a Delaware corporation.
Active Power, Inc.
 
Overview
 
Active Power designs, manufactures and services uninterruptible power supply (“UPS”) products and modular infrastructure solution (“MIS”) products that provide electrical power continuity and integrated infrastructure platforms for data centers and other mission critical applications.
 
Our products and solutions are designed to deliver continuous conditioned power during power disturbances and outages, voltage sags and surges, and provide ride-through power in the event of utility failure, supporting operations until utility power is restored or a longer term alternative power source, such as a diesel generator, is engaged. We believe our products offer an advantage over those of our competitors in the areas of power density (less space) and energy efficiency, total cost of ownership, system reliability, modular design, and the economically green benefits of our solutions.
 
We have sold our patented flywheel-based UPS products since 1999. As of December 31, 2012, we have shipped more than 3,500 flywheels in UPS system installations, delivering more than 900 megawatts of power to customers in 57 countries around the world, providing nearly 150 million runtime hours of operation.
 
In addition to selling stand-alone UPS products, we also manufacture and sell modular infrastructure solutions that provide critical power and infrastructure in a pre-packaged format and offer the same customer benefits with regard to operating efficiency, reliability and cost as our UPS products. These MIS products may include our UPS products as a component. For example, we design, manufacture and sell modular power infrastructure products that integrate our UPS products with other related equipment such as switchboards and backup diesel generators and is sold as a complete power solution for customers. We also integrate and build modular power and IT infrastructure solutions to specification, based on customer and other third party designs. These solutions are typically enclosures that have a fully built out interior – including electrical, cooling, monitoring and other elements – ready for the customer to add its IT racks and servers. They serve as the infrastructure for modular data center products which are self-contained fully functioning data centers once the customer adds its IT equipment. These industry emerging products can be deployed rapidly and at a lower cost than traditional brick-and-mortar solutions and are optimally suited for hyper-scale IT and cloud applications.
 
In 2012, 57% of our product revenue came from the sale of UPS products, and 43% from the sale of modular infrastructure solutions.
 
We are headquartered in Austin, Texas, with international offices in the United Kingdom, Germany, and China.
 
We believe a number of underlying macroeconomic trends place Active Power in a strong position to be one of the leading providers of critical power protection. These trends include:
 
 	●	increasing business costs of downtime;	
 
 	●	a rapidly expanding need for data center infrastructure;	

-1-

Table of Contents
 
 	●	ever-increasing demands placed on the public utility infrastructure;	
 
 	●	an inadequate investment in global utility infrastructure;	
 
 	●	rising costs of energy worldwide driven by volume of energy used; and	
 
 	●	an increasing demand for economically green solutions.	
 
We have evolved significantly since the company was founded in 1992. Our early focus was on research and development of the core products that continue to enable our business today. Over the past several years, we have focused our efforts on brand, markets, and channels of distribution. The technological foundation of Active Power has yielded more than 100 worldwide patents and a highly differentiated, cost-efficient product platform that we have evolved into an expanding suite of infrastructure solutions. As we go forward, it is critical for us to focus on both developing technology to maintain and grow our leadership position and expand our addressable markets and on building channels of distribution to have more avenues into the market.
 
Active Power has developed and implemented a go-to-market strategy to set the direction for our sales and marketing initiatives and plans around the following components:
 
 	●	Customer: Data Center Applications Across Vertical Markets	
 
 	●	Distribution: Partner Enabled Distribution Strategy Transacted Locally	
 
 	●	Geography: Global Markets served from four Centers of Operation	
 
 	●	Products: Continuous Power and Infrastructure Solutions	
 
 	●	Value: Efficient, Reliable, Green Solutions	
 
 	●	Service: Installation, Maintenance, Project Management and Other Professional Services	
 
As a result of this strategy, we have been successful in improving our operating performance, broadening our global footprint, diversifying our customer base, broadening our sales channels and partners, and moving higher up the customer value chain with innovative developments of our core underlying product technology.
Corporate Information
 
We were founded as a Texas corporation in 1992 and reincorporated in Delaware in 2000 prior to our initial public offering. Our principal executive offices are located at 2128 W. Braker Lane, BK12, Austin, Texas 78758 and our telephone number at that address is (512) 836-6464.  Our website address is www.activepower.com and we make our periodic and current reports that are filed with the Commission available, free of charge, on our website as soon as reasonably practicable after such material is electronically filed with, or furnished to, the Securities and Exchange Commission.  Information contained on our website does not constitute part of this prospectus.
 
Our common stock trades on The Nasdaq Capital Market under the symbol “ACPW.”

 
We own the registered trademarks ACTIVE POWER, CLEANSOURCE, COOLAIR, and POWERHOUSE in the United States and abroad. The ACTIVE POWER logo is a trademark of Active Power. All other trademarks, service marks or trade names referred to in this prospectus are the property of their respective owners.

-2-

Table of Contents
 
The Securities We May Offer
 
We may offer up to $50,000,000 of common stock, preferred stock, depositary shares, warrants, debt securities and/or units in one or more offerings and in any combination.  This prospectus provides you with a general description of the securities we may offer.  A prospectus supplement, which we will provide each time we offer securities, will describe the specific amounts, prices and terms of the securities we determine to offer.
 
Common Stock
 
We may offer shares of our common stock, par value $0.001 per share, either alone or underlying other registered securities convertible or exercisable into our common stock.  Each holder of our common stock is entitled to one vote for each share on all matters to be voted upon by the stockholders.  Holders of our common stock are entitled to receive ratably the dividends, if any, as may be declared from time to time by our board of directors out of funds legally available therefor. If there is a liquidation, dissolution or winding up of our company, holders of our common stock would be entitled to share in our assets remaining after the payment of liabilities and any preferential rights of any outstanding preferred stock.  The holders of common stock have no preemptive rights.  Currently, we do not pay a dividend and do not anticipate paying cash dividends in the foreseeable future.
 
Preferred Stock and Depositary Shares
 
Under the terms of our amended and restated certificate of incorporation, our board of directors is authorized to issue shares of preferred stock in one or more series without stockholder approval. Our board of directors has the discretion to determine the rights, preferences, privileges and restrictions, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences, of each series of preferred stock.
 
We may also issue fractional shares of preferred stock that will be represented by depositary shares and depositary receipts.
 
Each series of preferred stock, depositary shares or depositary receipts, if issued, will be more fully described in the particular prospectus supplement that will accompany this prospectus, including redemption provisions, rights in the event of our liquidation, dissolution or winding up, voting rights and rights to convert into common stock. We do not have any shares of our preferred stock, depositary shares or depositary receipts presently outstanding.
 
Warrants
 
We may issue warrants for the purchase of common stock, preferred stock or debt securities.  We may issue warrants independently or together with other securities.
 
Debt Securities
 
We may offer secured or unsecured obligations in the form of one or more series of senior or subordinated debt.  The senior debt securities and the subordinated debt securities are together referred to in this prospectus as the “debt securities.”  The subordinated debt securities generally will be entitled to payment only after payment of our senior debt.  Senior debt generally includes all debt for money borrowed by us, except debt that is stated in the instrument governing the terms of that debt to be not senior to, or to have the same rank in right of payment as, or to be expressly junior to, the subordinated debt securities.  We may issue debt securities that are convertible into shares of our common stock.
 
The senior and subordinated debt securities will be issued under separate indentures between us and a trustee.  We have summarized the general features of the debt securities to be governed by the indentures.  These indentures have been filed as exhibits to the registration statement of which this prospectus forms a part.  We encourage you to read these indentures.  Instructions on how you can get copies of these documents are provided under the heading “Where You Can Find More Information.”
 
Units
 
We may issue units comprised of one or more of the other classes of securities issued by us as described in this prospectus in any combination. Each unit will be issued so that the holder of the unit is also the holder of each security included in the unit.

-3-

Table of Contents
 
RISK FACTORS
 
An investment in our securities involves a high degree of risk.  The prospectus supplement applicable to each offering of our securities will contain a discussion of the risks applicable to an investment in our securities.  Prior to making a decision about investing in our securities, you should carefully consider the specific factors discussed under the heading “Risk Factors” in the applicable prospectus supplement, together with all of the other information contained or incorporated by reference in the prospectus supplement or appearing or incorporated by reference in this prospectus.  You should also consider the risks, uncertainties and assumptions discussed under Item 1A, “Risk Factors,” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2012 and any updates described in our Quarterly Reports on Form 10-Q, all of which are incorporated herein by reference, and may be amended, supplemented or superseded from time to time by other reports we file with the SEC in the future and any prospectus supplement related to a particular offering.   The occurrence of any of these risks might cause you to lose all or part of your investment in the offered securities.
 
FORWARD-LOOKING STATEMENTS
 
This prospectus, each prospectus supplement and the information incorporated by reference in this prospectus and each prospectus supplement contain certain statements that constitute “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. The words “anticipate,” “expect,” “believe,” “goal,” “plan,” “intend,” “estimate,” “may,” “will,” and similar expressions and variations thereof are intended to identify forward-looking statements, but are not the exclusive means of identifying such statements. Those statements appear in this prospectus, any accompanying prospectus supplement and the documents incorporated herein and therein by reference, particularly in the sections entitled “Prospectus Summary,” “Risk Factors,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and “Business,” and include statements regarding the intent, belief or current expectations of the company and management that are subject to known and unknown risks, uncertainties and assumptions and other factors that could cause actual results and the timing of certain events to differ materially from future results expressed or implied by such forward-looking statements.   Factors that could cause or contribute to such differences include, but are not limited to those discussed in the section titled “Risk Factors” set forth above.
 
This prospectus, any prospectus supplement and the information incorporated by reference in this prospectus and any prospectus supplement also contain statements that are based on management’s current expectations and beliefs, including estimates and projections about our company, industry, financial condition, results of operations and other matters. These statements are not guarantees of future performance and are subject to numerous risks, uncertainties, and assumptions that are difficult to predict.
 
Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified, you should not rely upon forward-looking statements as predictions of future events. The events and circumstances reflected in the forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the forward-looking statements. Except as required by applicable law, including the securities laws of the United States and the rules and regulations of the SEC, we do not plan to publicly update or revise any forward-looking statements contained herein after we distribute this prospectus, whether as a result of any new information, future events or otherwise.

-4-

Table of Contents
 
RATIO OF EARNINGS TO FIXED CHARGES
 
The following table sets forth our ratio of earnings to fixed charges for each of the years ended December 31, 2012, 2011, 2010, 2009 and 2008.  The following should be read in conjunction with our consolidated financial statements, including the notes thereto, and the other financial information included or incorporated by reference herein.  See Exhibit 12.1 hereto for additional detail regarding the computation of the deficiency of earnings to cover fixed charges.

 	 	Fiscal Year Ended December 31,	 	
 	 	2012	 	 	2011	 	 	2010	 	 	2009	 	 	2008	 	
Ratio of earnings to fixed charges (1)	 	 	—	 	 	 	—	 	 	 	—	 	 	 	—	 	 	 	—	 	

 
 	(1)	The ratio of earnings to fixed charges has been computed on a consolidated basis. “Earnings” consists of net income before income taxes plus fixed charges. “Fixed charges” consist of interest expense plus the portion of interest expense under operating leases deemed by us to be representative of the interest factor.	
 
For the years ended December 31, 2012, 2011, 2010, 2009 and 2008, our earnings were insufficient to cover fixed charges by $1.9 million, $7.1 million, $4.0 million, $11.0 million and $13.4 million, respectively.
 
As of the date of this prospectus, we have no shares of preferred stock outstanding, and consequently, our ratio of earnings to preferred share dividends and ratio of earnings to fixed charges would be identical.
USE OF PROCEEDS

Unless otherwise indicated in the prospectus supplement, we will use the net proceeds from the sale of securities offered by this prospectus for general corporate purposes, which may include working capital, capital expenditures, other corporate expenses and acquisitions of complementary products, technologies or businesses. The timing and amount of our actual expenditures will be based on many factors, including cash flows from operations and the anticipated growth of our business.  As a result, unless otherwise indicated in the prospectus supplement, our management will have broad discretion to allocate the net proceeds of the offerings.  Pending their ultimate use, we intend to invest the net proceeds in short-term, investment-grade, interest-bearing instruments.

-5-

Table of Contents
DESCRIPTION OF CAPITAL STOCK
 
The following information describes our common stock and preferred stock, as well as certain provisions of our restated certificate of incorporation and bylaws. This description is only a summary. You should also refer to our certificate of incorporation and bylaws, which have been filed with the SEC as exhibits to our registration statement, of which this prospectus forms a part.
General
 
Our authorized capital stock consists of 30,000,000 shares of common stock with a $0.001 par value per share, and 2,000,000 shares of undesignated preferred stock with a $0.001 par value per share.  Our board of directors may establish the rights and preferences of the preferred stock from time to time. As of February 28, 2013, there were 19,233,281 shares of common stock issued and outstanding.
 
The following is a summary of the material provisions of the common stock and preferred stock provided for in our restated certificate of incorporation and bylaws.  For additional detail about our capital stock, please refer to our certificate of incorporation and bylaws, each as amended.
Common Stock
 
The holders of common stock are entitled to one vote per share on all matters to be voted upon by the stockholders. Subject to preferences that may be applicable to any outstanding preferred stock, the holders of common stock are entitled to receive ratably any dividends or other distributions that may be declared from time to time by the board of directors out of funds legally available for that purpose. However, we are not currently paying any dividends. In the event of our liquidation, dissolution or winding up, the holders of common stock are entitled to share ratably in all assets remaining after payment of liabilities, subject to prior distribution rights of preferred stock then outstanding. The common stock has no preemptive or conversion rights or other subscription rights. There are no redemption or sinking fund provisions applicable to the common stock.
 
All outstanding shares of common stock are fully paid and non-assessable.
Preferred Stock
 
Pursuant to our restated certificate of incorporation, our board of directors has the authority, without action by our stockholders, to designate and issue up to 2,000,000 shares of preferred stock in one or more series. Of these authorized shares of preferred stock, 80,000 shares have been designated as “Series A Junior Participating Preferred Stock,” the rights, preferences and privileges of which are set forth in the Certificate of Designation of Series A Junior Participating Preferred Stock of Active Power filed with the Secretary of State of Delaware on December 18, 2001. The shares of Series A Junior Participating Preferred Stock were issuable upon exercise of certain rights under the Rights Agreement dated December 13, 2001 between us and EquiServe Trust N.A. All such rights, as well as the Rights Agreement, have expired and were terminated by the terms of the Rights Agreement.  The board of directors may also designate the rights, preferences and privileges of each series of preferred stock, any or all of which may be greater than the rights of the common stock.
 
It is not possible to state the actual effect of the issuance of any shares of preferred stock upon the rights of holders of the common stock until the board of directors determines the specific rights of the holders of the preferred stock.

-6-

Table of Contents
 
 However, these effects might include:
 
 	●	restricting dividends on the common stock;	
 
 	●	diluting the voting power of the common stock;	
 
 	●	impairing the liquidation rights of the common stock; and	
 
 	●	delaying or preventing a change in control of our company without further action by the stockholders.	
 
This description of the terms of the preferred stock is not complete and will be subject to and qualified by the certificate of designation relating to any applicable series of preferred stock.
 
Under the terms of our restated certificate of incorporation, our board of directors is authorized to issue shares of preferred stock in one or more series without stockholder approval. Our board of directors has the discretion to determine the rights, preferences, privileges and restrictions, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences, of each series of preferred stock.  There are no restrictions presently on the repurchase or redemption of any shares of our preferred stock.
 
The prospectus supplement for a series of preferred stock will specify:
 
 	●	the maximum number of shares;	
 
 	●	the designation of the shares;	
 
 	●	the annual dividend rate, if any, whether the dividend rate is fixed or variable, the date or dates on which dividends will accrue, the dividend payment dates, and whether dividends will be cumulative;	
 
 	●	the price and the terms and conditions for redemption, if any, including redemption at our option or at the option of the holders, including the time period for redemption, and any accumulated dividends or premiums;	
 
 	●	the liquidation preference, if any, and any accumulated dividends upon the liquidation, dissolution or winding up of our affairs;	
 
 	●	any sinking fund or similar provision, and, if so, the terms and provisions relating to the purpose and operation of the fund;	
 
 	●	the terms and conditions, if any, for conversion or exchange of shares of any other class or classes of our capital stock or any series of any other class or classes, or of any other series of the same class, or any other securities or assets, including the price or the rate of conversion or exchange and the method, if any, of adjustment;	
 
 	●	the voting rights; and	
 
 	●	any or all other preferences and relative, participating, optional or other special rights, privileges or qualifications, limitations or restrictions.	
 
The issuance of shares of preferred stock will affect, and may adversely affect, the rights of holders of common stock. It is not possible to state the actual effect of the issuance of any shares of preferred stock on the rights of holders of common stock until our board of directors determines the specific rights attached to that preferred stock. The effects of issuing additional preferred stock could include one or more of the following:
 
 	●	restricting dividends on the common stock;	
 
 	●	diluting the voting power of the common stock;	

-7-

Table of Contents
 
 	●	impairing the liquidation rights of the common stock; or	
 
 	●	delaying or preventing changes in control or management of our company.	
 
Preferred stock will be fully paid and nonassessable upon issuance.
Anti-Takeover Effects of Some Provisions of Delaware Law
 
Provisions of Delaware law and our currently in effect restated certificate of incorporation and bylaws could make the acquisition of our company through a tender offer, a proxy contest or other means more difficult and could make the removal of incumbent officers and directors more difficult. We expect these provisions to discourage coercive takeover practices and inadequate takeover bids and to encourage persons seeking to acquire control of our company to first negotiate with our board of directors. We believe that the benefits provided by our ability to negotiate with the proponent of an unfriendly or unsolicited proposal outweigh the disadvantages of discouraging these proposals. We believe the negotiation of an unfriendly or unsolicited proposal could result in an improvement of its terms.
 
We are subject to Section 203 of the Delaware General Corporation Law (the “DGCL”), an anti-takeover law. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a “business combination” with an “interested stockholder” for a period of three years following the date the person became an interested stockholder, unless:
 
 	●	prior to the date of the transaction, the board of directors of the corporation approved either the business combination or the transaction which resulted in the stockholder becoming an interested stockholder;	
 
 	●	the stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the number of shares outstanding (a) shares owned by persons who are directors and also officers, and (b) shares owned by employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or	
 
 	●	on or subsequent to the date of the transaction, the business combination is approved by the board and authorized at an annual or special meeting of stockholders, and not by written consent, by the affirmative vote of at least two-thirds of the outstanding voting stock that is not owned by the interested stockholder.	
 
Generally, a “business combination” includes a merger, asset or stock sale, or other transaction resulting in a financial benefit to the interested stockholder. An “interested stockholder” is a person who, together with affiliates and associates, owns or, within three years prior to the determination of interested stockholder status, did own 15% or more of a corporation’s outstanding voting securities. We expect the existence of this provision to have an anti-takeover effect with respect to transactions our board of directors does not approve in advance. We also anticipate that Section 203 may also discourage attempts that might result in a premium over the market price for the shares of common stock held by stockholders.  However, the board of directors has approved for purposes of Section 203(a)(1) of the DGCL Kinderhook Partners, LP becoming an “interested stockholder” (as defined in Section 203(c)(5) of the DGCL) and taken all other actions necessary so the restrictions contained in Section 203(a) applicable to a “business combination” (as defined in Section 203(c)(3) of the DGCL) did not apply to the closing of the Direct Offering or any of the transactions contemplated in connection therewith.

-8-

Table of Contents
Anti-Takeover Effects of Provisions of Our Charter Documents
 
Our currently in effect restated certificate of incorporation provides for our board of directors to be divided into three classes serving staggered terms. Approximately one-third of the board of directors will be elected each year. The provision for a classified board could prevent a party who acquires control of a majority of the outstanding voting stock from obtaining control of the board of directors until the second annual stockholders meeting following the date the acquirer obtains the controlling stock interest. The classified board provision could discourage a potential acquirer from making a tender offer or otherwise attempting to obtain control of our company and could increase the likelihood that incumbent directors will retain their positions. In accordance with our currently in effect amended and restated certificate of incorporation, directors may be removed by the affirmative vote of the holders of the outstanding shares of common stock only with cause.
 
Our currently in effect bylaws establish an advance notice procedure for stockholder proposals to be brought before an annual meeting of our stockholders, including proposed nominations of persons for election to the board of directors. At an annual meeting, stockholders may only consider proposals or nominations specified in the notice of meeting or brought before the meeting by or at the direction of the board of directors. Stockholders may also consider a proposal or nomination by a person who was a stockholder of record on the record date for the meeting, who is entitled to vote at the meeting and who has given to our Secretary timely written notice, in proper form, of his or her intention to bring that business before the meeting. The bylaws do not give the board of directors the power to approve or disapprove stockholder nominations of candidates or proposals regarding other business to be conducted at a special or annual meeting of the stockholders. However, our bylaws may have the effect of precluding the conduct of business at a meeting if the proper procedures are not followed. These provisions may also discourage or deter a potential acquirer from conducting a solicitation of proxies to elect the acquirer’s own slate of directors or otherwise attempting to obtain control of our company.
 
Our bylaws provide that only our board of directors may call a special meeting of stockholders. Because our stockholders do not have the right to call a special meeting, a stockholder could not force stockholder consideration of a proposal over the opposition of the board of directors by calling a special meeting of stockholders prior to such time as a majority of the board of directors believed the matter should be considered or until the next annual meeting provided that the requestor met the notice requirements. The restriction on the ability of stockholders to call a special meeting means that a proposal to replace the board also could be delayed until the next annual meeting.
 
Our currently in effect restated certificate of incorporation does not allow stockholders to act by written consent without a meeting. Without the availability of stockholder’s actions by written consent, a holder controlling a majority of our capital stock would not be able to amend our amended bylaws or remove directors without holding a stockholders’ meeting. The holder would have to obtain the consent of a majority of the board of directors to call a stockholders’ meeting and satisfy the notice periods determined by the board of directors.
Transfer Agent and Registrar
 
Our transfer agent and registrar for our common stock is American Stock Transfer & Trust Company, LLC. Its address is 59 Maiden Lane, Plaza Level, New York, New York 10038.
Listing
 
Our common stock is listed on The Nasdaq Capital Market under the trading symbol “ACPW.”

-9-

Table of Contents
 
DESCRIPTION OF THE DEPOSITARY SHARES
General
 
At our option, we may elect to offer fractional shares of preferred stock, rather than full shares of preferred stock.  If we do elect to offer fractional shares of preferred stock, we will issue receipts for depositary shares and each of these depositary shares will represent a fraction of a share of a particular series of preferred stock, as specified in the applicable prospectus supplement.  Each owner of a depositary share will be entitled, in proportion to the applicable fractional interest in shares of preferred stock underlying that depositary share, to all rights and preferences of the preferred stock underlying that depositary share.  These rights may include dividend, voting, redemption and liquidation rights.
 
The shares of preferred stock underlying the depositary shares will be deposited with a bank or trust company selected by us to act as depositary, under a deposit agreement by and among us, the depositary and the holders of the depositary receipts.  The depositary will be the transfer agent, registrar and dividend disbursing agent for the depositary shares.
 
The depositary shares will be evidenced by depositary receipts issued pursuant to the depositary agreement.  Holders of depositary receipts agree to be bound by the deposit agreement, which requires holders to take certain actions such as filing proof of residence and paying certain charges.
 
The summary of terms of the depositary shares contained in this prospectus is not complete, and is subject to modification in any prospectus supplement for any issuance of depositary shares.  You should refer to the forms of the deposit agreement, our certificate of incorporation and the certificate of designation that are, or will be, filed with the SEC for the applicable series of preferred stock.
Dividends
 
The depositary will distribute cash dividends or other cash distributions, if any, received in respect of the series of preferred stock underlying the depositary shares to the record holders of depositary receipts in proportion to the number of depositary shares owned by those holders on the relevant record date.  The relevant record date for depositary shares will be the same date as the record date for the preferred stock.
 
In the event of a distribution other than in cash, the depositary will distribute property received by it to the record holders of depositary receipts that are entitled to receive the distribution, unless the depositary determines that it is not feasible to make the distribution.  If this occurs, the depositary, with our approval, may adopt another method for the distribution, including selling the property and distributing the net proceeds to the holders.
Liquidation preference
 
If a series of preferred stock underlying the depositary shares has a liquidation preference, in the event of our voluntary or involuntary liquidation, dissolution or winding up, holders of depositary shares will be entitled to receive the fraction of the liquidation preference accorded each share of the applicable series of preferred stock, as set forth in the applicable prospectus supplement.
Redemption
 
If a series of preferred stock underlying the depositary shares is subject to redemption, the depositary shares will be redeemed from the proceeds received by the depositary resulting from the redemption, in whole or in part, of the preferred stock held by the depositary.  Whenever we redeem any preferred stock held by the depositary, the depositary will redeem, as of the same redemption date, the number of depositary shares representing the preferred stock so redeemed.  The depositary will mail the notice of redemption to the record holders of the depositary receipts promptly upon receiving the notice from us and not fewer than 20 or more than 60 days, unless otherwise provided in the applicable prospectus supplement, prior to the date fixed for redemption of the preferred stock.

-10-

Table of Contents
 
Voting
 
Upon receipt of notice of any meeting at which the holders of preferred stock are entitled to vote, the depositary will mail the information contained in the notice of meeting to the record holders of the depositary receipts underlying the preferred stock.  Each record holder of those depositary receipts on the record date will be entitled to instruct the depositary as to the exercise of the voting rights pertaining to the amount of preferred stock underlying that holder’s depositary shares.  The record date for the depositary will be the same date as the record date for the preferred stock.  The depositary will, to the extent practicable, vote the preferred stock underlying the depositary shares in accordance with these instructions.  We will agree to take all action that may be deemed necessary by the depositary in order to enable the depositary to vote the preferred stock in accordance with these instructions.  The depositary will not vote the preferred stock to the extent that it does not receive specific instructions from the holders of depositary receipts.
Withdrawal of preferred stock
 
Owners of depositary shares will be entitled to receive upon surrender of depositary receipts at the principal office of the depositary and payment of any unpaid amount due to the depositary, the number of whole shares of preferred stock underlying their depositary shares.
 
Partial shares of preferred stock will not be issued.  Holders of preferred stock will not be entitled to deposit the shares under the deposit agreement or to receive depositary receipts evidencing depositary shares for the preferred stock.
Amendment and termination of the deposit agreement
 
The form of depositary receipt evidencing the depositary shares and any provision of the deposit agreement may be amended by agreement between the depositary and us.  However, any amendment which materially and adversely alters the rights of the holders of depositary shares, other than fee changes, will not be effective unless the amendment has been approved by at least a majority of the outstanding depositary shares.  The deposit agreement may be terminated by the depositary or us only if:
 
 	●	all outstanding depositary shares have been redeemed; or	
 
 	●	there has been a final distribution of the preferred stock in connection with our dissolution and such distribution has been made to all the holders of depositary shares.	

Charges of depositary
 
We will pay all transfer and other taxes and governmental charges arising solely from the existence of the depositary arrangement.  We will also pay charges of the depositary in connection with:
 
 	●	the initial deposit of the preferred stock;	
 
 	●	the initial issuance of the depositary shares;	
 
 	●	any redemption of the preferred stock; and	
 
 	●	all withdrawals of preferred stock by owners of depositary shares.	

-11-

Table of Contents
 
Holders of depositary receipts will pay transfer, income and other taxes and governmental charges and other specified charges as provided in the deposit agreement for their accounts.  If these charges have not been paid, the depositary may:
 
 	●	refuse to transfer depositary shares;	
 
 	●	withhold dividends and distributions; and	
 
 	●	sell the depositary shares evidenced by the depositary receipt.	

Miscellaneous
 
The depositary will forward to the holders of depositary receipts all reports and communications we deliver to the depositary that we are required to furnish to the holders of the preferred stock.  In addition, the depositary will make available for inspection by holders of depositary receipts at the principal office of the depositary, and at such other places as it may from time to time deem advisable, any reports and communications we deliver to the depositary as the holder of preferred stock.
 
Neither the depositary nor we will be liable if either the depositary or we are prevented or delayed by law or any circumstance beyond the control of either the depositary or us in performing our respective obligations under the deposit agreement.  Our obligations and the depositary’s obligations will be limited to the performance in good faith of our or the depositary’s respective duties under the deposit agreement.  Neither the depositary nor we will be obligated to prosecute or defend any legal proceeding in respect of any depositary shares or preferred stock unless satisfactory indemnity is furnished.  The depositary and we may rely on:
 
 	●	written advice of counsel or accountants;	
 
 	●	information provided by holders of depositary receipts or other persons believed in good faith to be competent to give such information; and	
 
 	●	documents believed to be genuine and to have been signed or presented by the proper party or parties.	

Resignation and removal of depositary
 
The depositary may resign at any time by delivering a notice to us.  We may remove the depositary at any time.  Any such resignation or removal will take effect upon the appointment of a successor depositary and its acceptance of such appointment.  The successor depositary must be appointed within 60 days after delivery of the notice for resignation or removal.  The successor depositary must be a bank and trust company having its principal office in the United States of America and having a combined capital and surplus of at least $100,000,000.
Federal income tax consequences
 
Owners of the depositary shares will be treated for U.S. federal income tax purposes as if they were owners of the preferred stock underlying the depositary shares.  As a result, owners will be entitled to take into account for U.S. federal income tax purposes and deductions to which they would be entitled if they were holders of such preferred stock.  No gain or loss will be recognized for U.S. federal income tax purposes upon the withdrawal of preferred stock in exchange for depositary shares.  The tax basis of each share of preferred stock to an exchanging owner of depositary shares will, upon such exchange, be the same as the aggregate tax basis of the depositary shares exchanged.  The holding period for preferred stock in the hands of an exchanging owner of depositary shares will include the period during which such person owned such depositary shares.

-12-

Table of Contents
 
DESCRIPTION OF THE WARRANTS
General
 
We may issue warrants for the purchase of our debt securities, preferred stock or common stock, or any combination thereof.  Warrants may be issued independently or together with our debt securities, preferred stock or common stock and may be attached to or separate from any offered securities.  Each series of warrants will be issued under a separate warrant agreement to be entered into between us and a bank or trust company, as warrant agent.  The warrant agent will act solely as our agent in connection with the warrants.  The warrant agent will not have any obligation or relationship of agency or trust for or with any holders or beneficial owners of warrants.  This summary of certain provisions of the warrants is not complete.  For the terms of a particular series of warrants, you should refer to the prospectus supplement for that series of warrants and the warrant agreement for that particular series.
Debt warrants
 
The prospectus supplement relating to a particular issue of warrants to purchase debt securities will describe the terms of the debt warrants, including the following:
 
 	●	the title of the debt warrants;	
 
 	●	the offering price for the debt warrants, if any;	
 
 	●	the aggregate number of the debt warrants;	
 
 	●	the designation and terms of the debt securities, including any conversion rights, purchasable upon exercise of the debt warrants;	
 
 	●	if applicable, the date from and after which the debt warrants and any debt securities issued with them will be separately transferable;	
 
 	●	the principal amount of debt securities that may be purchased upon exercise of a debt warrant and the exercise price for the warrants, which may be payable in cash, securities or other property;	
 
 	●	the dates on which the right to exercise the debt warrants will commence and expire;	
 
 	●	if applicable, the minimum or maximum amount of the debt warrants that may be exercised at any one time;	
 
 	●	whether the debt warrants represented by the debt warrant certificates or debt securities that may be issued upon exercise of the debt warrants will be issued in registered or bearer form;	
 
 	●	information with respect to book-entry procedures, if any; the currency or currency units in which the offering price, if any, and the exercise price are payable;	
 
 	●	if applicable, a discussion of material U.S. federal income tax considerations;	
 
 	●	the antidilution provisions of the debt warrants, if any;	
 
 	●	the redemption or call provisions, if any, applicable to the debt warrants;	
 
 	●	any provisions with respect to the holder’s right to require us to repurchase the debt warrants upon a change in control or similar event; and	
 
 	●	any additional terms of the debt warrants, including procedures, and limitations relating to the exchange, exercise and settlement of the debt warrants.	

-13-

Table of Contents
 
Debt warrant certificates will be exchangeable for new debt warrant certificates of different denominations.  Debt warrants may be exercised at the corporate trust office of the warrant agent or any other office indicated in the prospectus supplement.  Prior to the exercise of their debt warrants, holders of debt warrants will not have any of the rights of holders of the debt securities purchasable upon exercise and will not be entitled to payment of principal or any premium, if any, or interest on the debt securities purchasable upon exercise.
Equity warrants
 
The prospectus supplement relating to a particular series of warrants to purchase our common stock or preferred stock will describe the terms of the warrants, including the following:
 
 	●	the title of the warrants;	
 
 	●	the offering price for the warrants, if any;	
 
 	●	the aggregate number of warrants;	
 
 	●	the designation and terms of the common stock or preferred stock that may be purchased upon exercise of the warrants;	
 
 	●	if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each security;	
 
 	●	if applicable, the date from and after which the warrants and any securities issued with the warrants will be separately transferable;	
 
 	●	the number of shares of common stock or preferred stock that may be purchased upon exercise of a warrant and the exercise price for the warrants;	
 
 	●	the dates on which the right to exercise the warrants shall commence and expire;	
 
 	●	if applicable, the minimum or maximum amount of the warrants that may be exercised at any one time;	
 
 	●	the currency or currency units in which the offering price, if any, and the exercise price are payable;	
 
 	●	if applicable, a discussion of material U.S. federal income tax considerations;	
 
 	●	the antidilution provisions of the warrants, if any;	
 
 	●	the redemption or call provisions, if any, applicable to the warrants;	
 
 	●	any provisions with respect to the holder’s right to require us to repurchase the warrants upon a change in control or similar event; and	
 
 	●	any additional terms of the warrants, including procedures, and limitations relating to the exchange, exercise and settlement of the warrants.	

-14-

Table of Contents
 
Holders of equity warrants will not be entitled:
 
 	●	to vote, consent or receive dividends;	
 
 	●	receive notice as stockholders with respect to any meeting of stockholders for the election of our directors or any other matter; or	
 
 	●	exercise any rights as stockholders of us.	

-15-

Table of Contents
 
DESCRIPTION OF THE DEBT SECURITIES
 
The debt securities may be either secured or unsecured and will either be our senior debt securities or our subordinated debt securities.  The debt securities will be issued under one or more separate indentures between us and a trustee to be specified in an accompanying prospectus supplement.  Senior debt securities will be issued under a senior indenture and subordinated debt securities will be issued under a subordinated indenture.  Together, the senior indenture and the subordinated indenture are called indentures in this description.  This prospectus, together with the applicable prospectus supplement, will describe the terms of a particular series of debt securities.
 
The following is a summary of selected provisions and definitions of the indentures and debt securities to which any prospectus supplement may relate.  The summary of selected provisions of the indentures and the debt securities appearing below is not complete and is subject to, and qualified entirely by reference to, all of the provisions of the applicable indenture and certificates evidencing the applicable debt securities.  For additional information, you should look at the applicable indenture and the certificate evidencing the applicable debt security that is filed as an exhibit to the registration statement that includes the prospectus.  In this description of the debt securities, the words “we,” “us,” or “our” refer only to Active Power, Inc. and not to any of our subsidiaries, unless we expressly state or the context otherwise requires.
 
The following description sets forth selected general terms and provisions of the applicable indenture and debt securities to which any prospectus supplement may relate.  Other specific terms of the applicable indenture and debt securities will be described in the applicable prospectus supplement.  If any particular terms of the indenture or debt securities described in a prospectus supplement differ from any of the terms described below, then the terms described below will be deemed to have been superseded by that prospectus supplement.
General
 
Debt securities may be issued in separate series without limitation as to aggregate principal amount.  We may specify a maximum aggregate principal amount for the debt securities of any series.
 
We are not limited as to the amount of debt securities we may issue under the indentures.  Unless otherwise provided in a prospectus supplement, a series of debt securities may be reopened to issue additional debt securities of such series.
 
The prospectus supplement relating to a particular series of debt securities will set forth:
 
 	●	whether the debt securities are senior or subordinated;	
 
 	●	the offering price;	
 
 	●	the title;	
 
 	●	any limit on the aggregate principal amount;	
 
 	●	the person who shall be entitled to receive interest, if other than the record holder on the record date;	
 
 	●	the date or dates the principal will be payable;	
 
 	●	the interest rate or rates, which may be fixed or variable, if any, the date from which interest will accrue, the interest payment dates and the regular record dates, or the method for calculating the dates and rates;	
 
 	●	the place where payments may be made;	

-16-

Table of Contents
 
 	●	any mandatory or optional redemption provisions or sinking fund provisions and any applicable redemption or purchase prices associated with these provisions;	
 
 	●	if issued other than in denominations of U.S. $1,000 or any multiple of U.S. $1,000, the denominations in which the debt securities shall be issuable;	
 
 	●	if applicable, the method for determining how the principal, premium, if any, or interest will be calculated by reference to an index or formula;	
 
 	●	if other than U.S. currency, the currency or currency units in which principal, premium, if any, or interest will be payable and whether we or a holder may elect payment to be made in a different currency;	
 
 	●	the portion of the principal amount that will be payable upon acceleration of maturity, if other than the entire principal amount;	
 
 	●	if the principal amount payable at stated maturity will not be determinable as of any date prior to stated maturity, the amount or method for determining the amount which will be deemed to be the principal amount;	
 
 	●	if applicable, whether the debt securities shall be subject to the defeasance provisions described below under “Satisfaction and discharge; defeasance” or such other defeasance provisions specified in the applicable prospectus supplement for the debt securities;	
 
 	●	any conversion or exchange provisions;	
 
 	●	whether the debt securities will be issuable in the form of a global security;	
 
 	●	the deletion, addition or change in any event of default;	
 
 	●	any change or modification to the subordination provisions applicable to the subordinated debt securities if different from those described below under “Subordinated debt securities;”	
 
 	●	any deletion, addition or change in the covenants set forth in Article 10 of the indenture;	
 
 	●	any paying agents, authenticating agents, security registrars or other agents for the debt securities, if other than the trustee;	
 
 	●	any provisions relating to any security provided for the debt securities, including any provisions regarding the circumstances under which collateral may be released or substituted;	
 
 	●	any provisions granting special rights to holders when a specified event occurs;	
 
 	●	any special tax provisions that apply to the debt securities;	
 
 	●	with respect to the debt securities that do not bear interest, the dates for certain required reports to the applicable trustee;	
 
 	●	any and all additional, eliminated or changed terms that will apply to the debt securities; and	
 
 	●	any other terms of such debt securities.	

-17-

Table of Contents
 
Unless otherwise specified in the prospectus supplement, the debt securities will be registered debt securities.  Debt securities may be sold at a substantial discount below their stated principal amount, bearing no interest or interest at a rate which at time of issuance is below market rates.  The U.S. federal income tax considerations applicable to debt securities sold at a discount will be described in the applicable prospectus supplement.
Exchange and transfer
 
Debt securities may be transferred or exchanged at the office of the security registrar or at the office of any transfer agent designated by us.
 
We will not impose a service charge for any transfer or exchange, but we may require holders to pay any tax or other governmental charges associated with any transfer or exchange.
 
In the event of any partial redemption of debt securities of any series, we will not be required to:
 
 	●	issue, register the transfer of, or exchange, any debt security of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption and ending at the close of business on the day of the mailing; or	
 
 	●	register the transfer of or exchange any debt security of that series selected for redemption, in whole or in part, except the unredeemed portion being redeemed in part.	
 
We will appoint the trustee as the initial security registrar.  Any transfer agent, in addition to the security registrar initially designated by us, will be named in the prospectus supplement.  We may designate additional transfer agents or change transfer agents or change the office of the transfer agent.  However, we will be required to maintain a transfer agent in each place of payment for the debt securities of each series.
Global securities
 
The debt securities of any series may be represented, in whole or in part, by one or more global securities.  Each global security will:
 
 	●	be registered in the name of a depositary, or its nominee, that we will identify in a prospectus supplement;	
 
 	●	be deposited with the depositary or nominee or custodian; and	
 
 	●	bear any required legends.	
 
No global security may be exchanged in whole or in part for debt securities registered in the name of any person other than the depositary or any nominee unless:
 
 	●	the depositary has notified us that it is unwilling or unable to continue as depositary or has ceased to be qualified to act as depositary;	
 
 	●	an event of default is continuing with respect to the debt securities of the applicable series; or	
 
 	●	any other circumstance described in a prospectus supplement has occurred permitting or requiring the issuance of any such security.	

-18-

Table of Contents
 
As long as the depositary, or its nominee, is the registered owner of a global security, the depositary or nominee will be considered the sole owner and holder of the debt securities represented by the global security for all purposes under the indentures.  Except in the above limited circumstances, owners of beneficial interests in a global security will not be:
 
 	●	entitled to have the debt securities registered in their names;	
 
 	●	entitled to physical delivery of certificated debt securities; or	
 
 	●	considered to be holders of those debt securities under the indenture.	
 
Payments on a global security will be made to the depositary or its nominee as the holder of the global security.  Some jurisdictions have laws that require that certain purchasers of securities take physical delivery of such securities in definitive form.  These laws may impair the ability to transfer beneficial interests in a global security.
 
Institutions that have accounts with the depositary or its nominee are referred to as “participants.”  Ownership of beneficial interests in a global security will be limited to participants and to persons that may hold beneficial interests through participants.  The depositary will credit, on its book-entry registration and transfer system, the respective principal amounts of debt securities represented by the global security to the accounts of its participants.
 
Ownership of beneficial interests in a global security will be shown on and effected through records maintained by the depositary, with respect to participants’ interests, or any participant, with respect to interests of persons held by participants on their behalf.
 
Payments, transfers and exchanges relating to beneficial interests in a global security will be subject to policies and procedures of the depositary.  The depositary policies and procedures may change from time to time.  Neither any trustee nor we will have any responsibility or liability for the depositary’s or any participant’s records with respect to beneficial interests in a global security.
Payment and paying agents
 
Unless otherwise indicated in a prospectus supplement, the provisions described in this paragraph will apply to the debt securities.  Payment of interest on a debt security on any interest payment date will be made to the person in whose name the debt security is registered at the close of business on the regular record date.  Payment on debt securities of a particular series will be payable at the office of a paying agent or paying agents designated by us.  However, at our option, we may pay interest by mailing a check to the record holder.  The trustee will be designated as our initial paying agent.
 
We may also name any other paying agents in a prospectus supplement.  We may designate additional paying agents, change paying agents or change the office of any paying agent.  However, we will be required to maintain a paying agent in each place of payment for the debt securities of a particular series.
 
All moneys paid by us to a paying agent for payment on any debt security that remain unclaimed for a period ending the earlier of:
 
 	●	10 business days prior to the date the money would be turned over to the applicable state; or	
 
 	●	at the end of two years after such payment was due,	

will be repaid to us thereafter.  The holder may look only to us for such payment.

-19-

Table of Contents
 
No protection in the event of a change of control
 
Unless otherwise indicated in a prospectus supplement with respect to a particular series of debt securities, the debt securities will not contain any provisions that may afford holders of the debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction, whether or not such transaction results in a change in control.
Covenants
 
Unless otherwise indicated in a prospectus supplement with respect to a particular series of debt securities, the debt securities will not contain any financial or restrictive covenants.
Consolidation, merger and sale of assets
 
Unless we indicate otherwise in a prospectus supplement with respect to a particular series of debt securities, we may not consolidate with or merge into any other person (other than one of our subsidiaries), in a transaction in which we are not the surviving corporation, or convey, transfer or lease our properties and assets substantially as an entirety to, any person (other than a subsidiary of Active Power), unless:
 
 	●	the successor entity, if any, is a U.S. corporation, limited liability company, partnership, trust or other business entity;	
 
 	●	the successor entity assumes our obligations on the debt securities and under the indentures;	
 
 	●	immediately after giving effect to the transaction, no default or event of default shall have occurred and be continuing; and	
 
 	●	certain other conditions specified in the indenture are met.	

Events of default
 
Unless we indicate otherwise in a prospectus supplement, the following will be events of default for any series of debt securities under the indentures:
 
 	(1)	we fail to pay principal of or any premium on any debt security of that series when due;	
 
 	(2)	we fail to pay any interest on any debt security of that series for 30 days after it becomes due;	
 
 	(3)	we fail to deposit any sinking fund payment when due;	
 
 	(4)	we fail to perform any other covenant in the indenture and such failure continues for 90 days after we are given the notice required in the indentures; and	
 
 	(5)	certain events involving our bankruptcy, insolvency or reorganization.	
 
Additional or different events of default applicable to a series of debt securities may be described in a prospectus supplement.  An event of default of one series of debt securities is not necessarily an event of default for any other series of debt securities.
 
The trustee may withhold notice to the holders of any default, except defaults in the payment of principal, premium, if any, interest, any sinking fund installment on, or with respect to any conversion right of, the debt securities of such series.  However, the trustee must consider it to be in the interest of the holders of the debt securities of such series to withhold this notice.

-20-

Table of Contents
 
Unless we indicate otherwise in a prospectus supplement, if an event of default, other than an event of default described in clause (5) above, shall occur and be continuing with respect to any series of debt securities, either the trustee or the holders of at least 25 percent in aggregate principal amount of the outstanding securities of that series may declare the principal amount and premium, if any, of the debt securities of that series, or if any debt securities of that series are original issue discount securities, such other amount as may be specified in the applicable prospectus supplement, in each case together with accrued and unpaid interest, if any, thereon, to be due and payable immediately.
 
Unless we indicate otherwise in a prospectus supplement, if an event of default described in clause (5) above shall occur, the principal amount and premium, if any, of all the debt securities of that series, or if any debt securities of that series are original issue discount securities, such other amount as may be specified in the applicable prospectus supplement, in each case together with accrued and unpaid interest, if any, thereon, will automatically become immediately due and payable.  Any payment by us on the subordinated debt securities following any such acceleration will be subject to the subordination provisions described below under “Subordinated debt securities.”
 
Notwithstanding the foregoing, each indenture will provide that we may, at our option, elect that the sole remedy for an event of default relating to our failure to comply with our obligations described under the section entitled “Reports” below or our failure to comply with the requirements of Section 314(a)(1) of the Trust Indenture Act will for the first 180 days after the occurrence of such an event of default consist exclusively of the right to receive additional interest on the relevant series of debt securities at an annual rate equal to (i) 0.25% of the principal amount of such series of debt securities for the first 90 days after the occurrence of such event of default and (ii) 0.50% of the principal amount of such series of debt securities from the 91st day to, and including, the 180th day after the occurrence of such event of default, which we call “additional interest.”  If we so elect, the additional interest will accrue on all outstanding debt securities from and including the date on which such event of default first occurs until such violation is cured or waived and shall be payable on each relevant interest payment date to holders of record on the regular record date immediately preceding the interest payment date.  On the 181st day after such event of default (if such violation is not cured or waived prior to such 181st day), the debt securities will be subject to acceleration as provided above.  In the event we do not elect to pay additional interest upon any such event of default in accordance with this paragraph, the debt securities will be subject to acceleration as provided above.
 
In order to elect to pay the additional interest as the sole remedy during the first 180 days after the occurrence of any event of default relating to the failure to comply with the reporting obligations in accordance with the preceding paragraph, we must notify all holders of debt securities and the trustee and paying agent of such election prior to the close of business on the first business day following the date on which such event of default occurs.  Upon our failure to timely give such notice or pay the additional interest, the debt securities will be immediately subject to acceleration as provided above.
 
After acceleration, the holders of a majority in aggregate principal amount of the outstanding securities of that series may, under certain circumstances, rescind and annul such acceleration if all events of default, other than the non-payment of accelerated principal, or other specified amounts or interest, have been cured or waived.
 
Other than the duty to act with the required care during an event of default, the trustee will not be obligated to exercise any of its rights or powers at the request of the holders unless the holders shall have offered to the trustee reasonable indemnity.  Generally, the holders of a majority in aggregate principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee.

-21-

Table of Contents
 
A holder of debt securities of any series will not have any right to institute any proceeding under the indentures, or for the appointment of a receiver or a trustee, or for any other remedy under the indentures, unless:
 
 	(1)	the holder has previously given to the trustee written notice of a continuing event of default with respect to the debt securities of that series;	
 
 	(2)	the holders of at least 25 percent in aggregate principal amount of the outstanding debt securities of that series have made a written request and have offered reasonable indemnity to the trustee to institute the proceeding; and	
 
 	(3)	the trustee has failed to institute the proceeding and has not received direction inconsistent with the original request from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series within 60 days after the original request.	
 
Holders may, however, sue to enforce the payment of principal, premium or interest on any debt security on or after the due date or to enforce the right, if any, to convert any debt security (if the debt security is convertible) without following the procedures listed in (1) through (3) above.
 
We will furnish the trustee an annual statement from our officers as to whether or not we are in default in the performance of the conditions and covenants under the indenture and, if so, specifying all known defaults.
Modification and waiver
 
Unless we indicate otherwise in a prospectus supplement, the applicable trustee and we may make modifications and amendments to an indenture with the consent of the holders of a majority in aggregate principal amount of the outstanding securities of each series affected by the modification or amendment.
 
We may also make modifications and amendments to the indentures for the benefit of holders without their consent, for certain purposes including, but not limited to:
 
 	●	to evidence the succession of another person to Active Power, or successive successions, and the assumption by any such successor of the covenants of Active Power in the indentures in compliance with Article 8 of the indentures;	
 
 	●	adding covenants;	
 
 	●	adding events of default;	
 
 	●	making certain changes to facilitate the issuance of the debt securities;	
 
 	●	to add to, change or eliminate any of the provisions of the indentures or more series of securities, provided that any such addition, change or elimination (A) shall neither (i) apply to any security of any series created prior to the execution of such supplemental indenture and entitled to the benefit of such provision nor (ii) modify the rights of the holder of any such security with respect to such provision or (B) shall become effective only when there is no such security outstanding;	
 
 	●	securing the debt securities;	
 
 	●	providing for guaranties of, or additional obligors on, the debt securities;	
 
 	●	to establish the form or term of debt securities as permitted by Sections 2.1 and 3.1 of the indenture;	
 
 	●	providing for a successor trustee or additional trustees;	

-22-

Table of Contents
 
 	●	conforming the indenture to the description of the securities set forth in this prospectus or the accompanying prospectus supplement;	
 
 	●	curing any ambiguity, defect or inconsistency; provided that such action shall not adversely affect the interest of the holders in any material respect;	
 
 	●	permitting or facilitating the defeasance and discharge of the debt securities;	
 
 	●	make such other provisions in regard to matters or questions arising under the indentures or under any supplemental indentures as our board of directors may deem necessary or desirable, and which does not in each case adversely affect the interests of the holders of the debt securities of a series; and	
 
 	●	comply with requirements of the U.S. Securities and Exchange Commission in order to effect or maintain the qualifications of the indentures under the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”).	
 
However, neither the trustee nor we may make any modification or amendment without the consent of the holder of each outstanding security of that series affected by the modification or amendment if such modification or amendment would:
 
 	●	change the stated maturity of the principal of, or any installment of principal or interest on, any debt security;	
 
 	●	reduce the principal, premium, if any, or interest on any debt security or any amount payable upon redemption or repurchase, whether at our option or the option of any holder, or reduce the amount of any sinking fund payments;	
 
 	●	reduce the principal of an original issue discount security or any other debt security payable on acceleration of maturity;	
 
 	●	change the place of payment or the currency in which any debt security is payable;	
 
 	●	impair the right to enforce any payment after the stated maturity or redemption date;	
 
 	●	if subordinated debt securities, modify the subordination provisions in a materially adverse manner to the holders;	
 
 	●	adversely affect the right to convert any debt security if the debt security is a convertible debt security; or	
 
 	●	change the provisions in the indenture that relate to modifying or amending the indenture.	

Satisfaction and discharge; defeasance
 
We may be discharged from our obligations on the debt securities, subject to limited exceptions, of any series that have matured or will mature or be redeemed within one year if we deposit enough money with the trustee to pay all the principal, interest and any premium due to the stated maturity date or redemption date of the debt securities.
 
Each indenture contains a provision that permits us to elect either or both of the following:
 
 	●	We may elect to be discharged from all of our obligations, subject to limited exceptions, with respect to any series of debt securities then outstanding.  If we make this election, the holders of the debt securities of the series will not be entitled to the benefits of the indenture, except for the rights of holders to receive payments on debt securities or the registration of transfer and exchange of debt securities and replacement of lost, stolen or mutilated debt securities.	
 
 	●	We may elect to be released from our obligations under some or all of any financial or restrictive covenants applicable to the series of debt securities to which the election relates and from the consequences of an event of default resulting from a breach of those covenants.	

-23-

Table of Contents
 
To make either of the above elections, we must irrevocably deposit in trust with the trustee enough money to pay in full the principal, interest and premium on the debt securities.  This amount may be made in cash and/or U.S. government obligations or, in the case of debt securities denominated in a currency other than U.S. dollars, cash in the currency in which such series of securities is denominated and/or foreign government obligations.  As a condition to either of the above elections, for debt securities denominated in U.S. dollars we must deliver to the trustee an opinion of counsel that the holders of the debt securities will not recognize income, gain or loss for U.S. federal income tax purposes as a result of the action.
 
With respect to debt securities of any series that are denominated in a currency other than United States dollars, “foreign government obligations” means:
 
 	●	direct obligations of the government that issued or caused to be issued the currency in which such securities are denominated and for the payment of which obligations its full faith and credit is pledged, or, with respect to debt securities of any series which are denominated in Euros, direct obligations of certain members of the European Union for the payment of which obligations the full faith and credit of such members is pledged, which in each case are not callable or redeemable at the option of the issuer thereof; or	
 
 	●	obligations of a person controlled or supervised by or acting as an agency or instrumentality of a government described in the bullet above the timely payment of which is unconditionally guaranteed as a full faith and credit obligation by such government, which are not callable or redeemable at the option of the issuer thereof.	

Notices
 
Notices to holders will be given by mail to the addresses of the holders in the security register.
Governing law
 
The indentures and the debt securities will be governed by, and construed under, the laws of the State of New York.
No personal liability of directors, officers, employees and stockholders
 
No incorporator, stockholder, employee, agent, officer, director or subsidiary of ours will have any liability for any obligations of ours, or because of the creation of any indebtedness under the debt securities, the indentures or supplemental indentures.  The indentures provide that all such liability is expressly waived and released as a condition of, and as a consideration for, the execution of such indentures and the issuance of the debt securities.
Regarding the trustee
 
The indentures limit the right of the trustee, should it become our creditor, to obtain payment of claims or secure its claims.
 
The trustee will be permitted to engage in certain other transactions with us.  However, if the trustee acquires any conflicting interest, and there is a default under the debt securities of any series for which it is trustee, the trustee must eliminate the conflict or resign.

-24-

Table of Contents
Subordinated debt securities
 
The following provisions will be applicable with respect to each series of subordinated debt securities, unless otherwise stated in the prospectus supplement relating to that series of subordinated debt securities.
 
The indebtedness evidenced by the subordinated debt securities of any series is subordinated, to the extent provided in the subordinated indenture and the applicable prospectus supplement, to the prior payment in full, in cash or other payment satisfactory to the holders of senior debt, of all senior debt, including any senior debt securities.
 
Upon any distribution of our assets upon any dissolution, winding up, liquidation or reorganization, whether voluntary or involuntary, marshalling of assets, assignment for the benefit of creditors, or in bankruptcy, insolvency, receivership or other similar proceedings, payments on the subordinated debt securities will be subordinated in right of payment to the prior payment in full in cash or other payment satisfactory to holders of senior debt of all senior debt.
 
In the event of any acceleration of the subordinated debt securities of any series because of an event of default with respect to the subordinated debt securities of that series, holders of any senior debt would be entitled to payment in full in cash or other payment satisfactory to holders of senior debt of all senior debt before the holders of subordinated debt securities are entitled to receive any payment or distribution.
 
In addition, the subordinated debt securities will be structurally subordinated to all indebtedness and other liabilities of our subsidiaries, including trade payables and lease obligations.  This occurs because our right to receive any assets of our subsidiaries upon their liquidation or reorganization, and your right to participate in those assets, will be effectively subordinated to the claims of that subsidiary’s creditors, including trade creditors, except to the extent that we are recognized as a creditor of such subsidiary.  If we are recognized as a creditor of that subsidiary, our claims would still be subordinate to any security interest in the assets of the subsidiary and any indebtedness of the subsidiary senior to us.
 
We are required to promptly notify holders of senior debt or their representatives under the subordinated indenture if payment of the subordinated debt securities is accelerated because of an event of default.
 
Under the subordinated indenture, we may also not make payment on the subordinated debt securities if:
 
 	●	a default in our obligations to pay principal, premium, if any, interest or other amounts on our senior debt occurs and the default continues beyond any applicable grace period, which we refer to as a payment default; or	
 
 	●	any other default occurs and is continuing with respect to designated senior debt that permits holders of designated senior debt to accelerate its maturity, which we refer to as a non-payment default, and the trustee receives a payment blockage notice from us or some other person permitted to give the notice under the subordinated indenture.	
 
We will resume payments on the subordinated debt securities:
 
 	●	in case of a payment default, when the default is cured or waived or ceases to exist, and	
 
 	●	in case of a nonpayment default, the earlier of when the default is cured or waived or ceases to exist or 179 days after the receipt of the payment blockage notice.	

-25-

Table of Contents
 
No new payment blockage period may commence on the basis of a nonpayment default unless 365 days have elapsed from the effectiveness of the immediately prior payment blockage notice.  No nonpayment default that existed or was continuing on the date of delivery of any payment blockage notice to the trustee shall be the basis for a subsequent payment blockage notice.
 
As a result of these subordination provisions, in the event of our bankruptcy, dissolution or reorganization, holders of senior debt may receive more, ratably, and holders of the subordinated debt securities may receive less, ratably, than our other creditors.  The subordination provisions will not prevent the occurrence of any event of default under the subordinated indenture.
 
The subordination provisions will not apply to payments from money or government obligations held in trust by the trustee for the payment of principal, interest and premium, if any, on subordinated debt securities pursuant to the provisions described under the section entitled “Satisfaction and discharge; defeasance,” if the subordination provisions were not violated at the time the money or government obligations were deposited into trust.
 
If the trustee or any holder receives any payment that should not have been made to them in contravention of subordination provisions before all senior debt is paid in full in cash or other payment satisfactory to holders of senior debt, then such payment will be held in trust for the holders of senior debt.
 
Senior debt securities will constitute senior debt under the subordinated indenture.
 
Additional or different subordination provisions may be described in a prospectus supplement relating to a particular series of debt securities.
Definitions
 
“Designated senior debt” means our obligations under any particular senior debt in which the instrument creating or evidencing the same or the assumption or guarantee thereof, or related agreements or documents to which we are a party, expressly provides that such indebtedness shall be designated senior debt for purposes of the subordinated indenture.  The instrument, agreement or other document evidencing any designated senior debt may place limitations and conditions on the right of such senior debt to exercise the rights of designated senior debt.
 
“Indebtedness” means the following, whether absolute or contingent, secured or unsecured, due or to become due, outstanding on the date of the indenture for such series of securities or thereafter created, incurred or assumed:
 
 	●	our indebtedness evidenced by a credit or loan agreement, note, bond, debenture or other written obligation;	
 
 	●	all of our obligations for money borrowed;	
 
 	●	all of our obligations evidenced by a note or similar instrument given in connection with the acquisition of any businesses, properties or assets of any kind,	
 
 	●	our obligations:	
 
 	●	as lessee under leases required to be capitalized on the balance sheet of the lessee under generally accepted accounting principles, or	
 
 	●	as lessee under leases for facilities, capital equipment or related assets, whether or not capitalized, entered into or leased for financing purposes;	
 
 	●	all of our obligations under interest rate and currency swaps, caps, floors, collars, hedge agreements, forward contracts or similar agreements or arrangements;	

-26-

Table of Contents
 
 	●	all of our obligations with respect to letters of credit, bankers’ acceptances and similar facilities, including reimbursement obligations with respect to the foregoing;	
 
 	●	all of our obligations issued or assumed as the deferred purchase price of property or services, but excluding trade accounts payable and accrued liabilities arising in the ordinary course of business;	
 
 	●	all obligations of the type referred to in the above clauses of another person, the payment of which, in either case, we have assumed or guaranteed, for which we are responsible or liable, directly or indirectly, jointly or severally, as obligor, guarantor or otherwise, or which are secured by a lien on our property; and	
 
 	●	renewals, extensions, modifications, replacements, restatements and refundings of, or any indebtedness or obligation issued in exchange for, any such indebtedness or obligation described in the above clauses of this definition.	
 
“Senior debt” means the principal of, premium, if any, and interest, including all interest accruing subsequent to the commencement of any bankruptcy or similar proceeding, whether or not a claim for post-petition interest is allowable as a claim in any such proceeding, and rent payable on or in connection with, and all fees and other amounts payable in connection with, our indebtedness.  However, senior debt shall not include:
 
 	●	any debt or obligation if its terms or the terms of the instrument under which or pursuant to which it is issued expressly provide that it shall not be senior in right of payment to the subordinated debt securities or expressly provide that such indebtedness is on the same basis or “junior” to the subordinated debt securities; or	
 
 	●	debt to any of our subsidiaries, a majority of the voting stock of which is owned, directly or indirectly, by us.	
 
“Subsidiary” means a corporation more than 50% of the outstanding voting stock of which is owned, directly or indirectly, by us or by one or more of our other subsidiaries or by a combination of us and our other subsidiaries.  For purposes of this definition, “voting stock” means stock or other similar interests which ordinarily has or have voting power for the election of directors, or persons performing similar functions, whether at all times or only so long as no senior class of stock or other interests has or have such voting power by reason of any contingency.

-27-

Table of Contents
 
DESCRIPTION OF THE UNITS
 
We may issue units comprised of one or more of the other classes of securities described in this prospectus in any combination. Each unit will be issued so that the holder of the unit is also the holder of each security included in the unit. Thus, the holder of a unit will have the rights and obligations of a holder of each included security. The units may be issued under unit agreements to be entered into between us and a unit agent, as detailed in the prospectus supplement relating to the units being offered. The prospectus supplement will describe:
 
 	●	the designation and terms of the units and of the securities comprising the units, including whether and under what circumstances the securities comprising the units may be held or transferred separately;	
 
 	●	a description of the terms of any unit agreement governing the units;	
 
 	●	a description of the provisions for the payment, settlement, transfer or exchange of the units;	
 
 	●	a discussion of material federal income tax considerations, if applicable; and	
 
 	●	whether the units if issued as a separate security will be issued in fully registered or global form.	
 
The descriptions of the units in this prospectus and in any prospectus supplement are summaries of the material provisions of the applicable agreements. These descriptions do not restate those agreements in their entirety and may not contain all the information that you may find useful. We urge you to read the applicable agreements because they, and not the summaries, define your rights as holders of the units. For more information, please review the forms of the relevant agreements, which will be filed with the SEC promptly after the offering of units and will be available as described under the heading “Where You Can Find More Information.”

-28-

Table of Contents
PLAN OF DISTRIBUTION
 
We may sell the securities offered through this prospectus (1) to or through underwriters or dealers, (2) directly to purchasers, including our affiliates, (3) through agents, or (4) through a combination of any these methods.  The securities may be distributed at a fixed price or prices, which may be changed, market prices prevailing at the time of sale, prices related to the prevailing market prices, or negotiated prices.  The prospectus supplement will include the following information:
 
 	●	the terms of the offering;	
 
 	●	the names of any underwriters or agents;	
 
 	●	the name or names of any managing underwriter or underwriters;	
 
 	●	the purchase price of the securities;	
 
 	●	the net proceeds from the sale of the securities;	
 
 	●	any delayed delivery arrangements;	
 
 	●	any underwriting discounts, commissions and other items constituting underwriters’ compensation;	
 
 	●	any initial public offering price;	
 
 	●	any discounts or concessions allowed or reallowed or paid to dealers; and	
 
 	●	any commissions paid to agents.	

Sale through underwriters or dealers
 
If underwriters are used in the sale, the underwriters will acquire the securities for their own account, including through underwriting, purchase, security lending or repurchase agreements with us.  The underwriters may resell the securities from time to time in one or more transactions, including negotiated transactions.  Underwriters may sell the securities in order to facilitate transactions in any of our other securities (described in this prospectus or otherwise), including other public or private transactions and short sales.  Underwriters may offer securities to the public either through underwriting syndicates represented by one or more managing underwriters or directly by one or more firms acting as underwriters.  Unless otherwise indicated in the prospectus supplement, the obligations of the underwriters to purchase the securities will be subject to certain conditions, and the underwriters will be obligated to purchase all the offered securities if they purchase any of them.  The underwriters may change from time to time any initial public offering price and any discounts or concessions allowed or reallowed or paid to dealers.  The prospectus supplement will include the names of the principal underwriters the respective amount of securities underwritten, the nature of the obligation of the underwriters to take the securities and the nature of any material relationship between an underwriter and us.
 
If dealers are used in the sale of securities offered through this prospectus, we will sell the securities to them as principals.  They may then resell those securities to the public at varying prices determined by the dealers at the time of resale.  The prospectus supplement will include the names of the dealers and the terms of the transaction.

-29-

Table of Contents
 
Direct sales and sales through agents
 
We may sell the securities offered through this prospectus directly.  In this case, no underwriters or agents would be involved.  Such securities may also be sold through agents designated from time to time.  The prospectus supplement will name any agent involved in the offer or sale of the offered securities and will describe any commissions payable to the agent by us.  Unless otherwise indicated in the prospectus supplement, any agent will agree to use its reasonable best efforts to solicit purchases for the period of its appointment.
 
We may sell the securities directly to institutional investors or others who may be deemed to be underwriters within the meaning of the Securities Act with respect to any sale of those securities.  The terms of any such sales will be described in the prospectus supplement.
Market making, stabilization and other transactions
 
Unless the applicable prospectus supplement states otherwise, each series of offered securities will be a new issue and will have no established trading market.  We may elect to list any series of offered securities on an exchange.  Any underwriters that we use in the sale of offered securities may make a market in such securities, but may discontinue such market making at any time without notice.  Therefore, we cannot assure you that the securities will have a liquid trading market.
 
Any underwriter may also engage in stabilizing transactions, syndicate covering transactions and penalty bids in accordance with Rule 104 under the Securities Exchange Act of 1934, as amended.  Stabilizing transactions involve bids to purchase the underlying security in the open market for the purpose of pegging, fixing or maintaining the price of the securities.  Syndicate covering transactions involve purchases of the securities in the open market after the distribution has been completed in order to cover syndicate short positions.
 
Penalty bids permit the underwriters to reclaim a selling concession from a syndicate member when the securities originally sold by the syndicate member are purchased in a syndicate covering transaction to cover syndicate short positions.  Stabilizing transactions, syndicate covering transactions and penalty bids may cause the price of the securities to be higher than it would be in the absence of the transactions.  The underwriters may, if they commence these transactions, discontinue them at any time.
Derivative transactions and hedging
 
We, the underwriters or other agents may engage in derivative transactions involving the securities.  These derivatives may consist of short sale transactions and other hedging activities.  The underwriters or agents may acquire a long or short position in the securities, hold or resell securities acquired and purchase options or futures on the securities and other derivative instruments with returns linked to or related to changes in the price of the securities.  In order to facilitate these derivative transactions, we may enter into security lending or repurchase agreements with the underwriters or agents.  The underwriters or agents may effect the derivative transactions through sales of the securities to the public, including short sales, or by lending the securities in order to facilitate short sale transactions by others.  The underwriters or agents may also use the securities purchased or borrowed from us or others (or, in the case of derivatives, securities received from us in settlement of those derivatives) to directly or indirectly settle sales of the securities or close out any related open borrowings of the securities.
Electronic auctions
 
We may also make sales through the Internet or through other electronic means.  Since we may from time to time elect to offer securities directly to the public, with or without the involvement of agents, underwriters or dealers, utilizing the Internet or other forms of electronic bidding or ordering systems for the pricing and allocation of such securities, you should pay particular attention to the description of that system we will provide in a prospectus supplement.

-30-

Table of Contents
 
Such electronic system may allow bidders to directly participate, through electronic access to an auction site, by submitting conditional offers to buy that are subject to acceptance by us, and which may directly affect the price or other terms and conditions at which such securities are sold.  These bidding or ordering systems may present to each bidder, on a so-called “real-time” basis, relevant information to assist in making a bid, such as the clearing spread at which the offering would be sold, based on the bids submitted, and whether a bidder’s individual bids would be accepted, prorated or rejected.  For example, in the case of a debt security, the clearing spread could be indicated as a number of “basis points” above an index treasury note.  Of course, many pricing methods can and may also be used.
 
Upon completion of such an electronic auction process, securities will be allocated based on prices bid, terms of bid or other factors.  The final offering price at which securities would be sold and the allocation of securities among bidders would be based in whole or in part on the results of the Internet or other electronic bidding process or auction.
General information
 
Agents, underwriters, and dealers may be entitled, under agreements entered into with us, to indemnification by us against certain liabilities, including liabilities under the Securities Act.

-31-

Table of Contents
 
LEGAL MATTERS
 
The validity of the securities offered by this prospectus will be passed upon by Wilson Sonsini Goodrich & Rosati, Professional Corporation, Austin, Texas.
EXPERTS
 
The financial statements and management’s assessment of the effectiveness of internal control over financial reporting incorporated by reference in this prospectus and elsewhere in the registration statement have been so incorporated by reference in reliance upon the reports of Grant Thornton LLP, independent registered public accountants, upon the authority of said firm as experts in accounting and auditing in giving said report.
 
WHERE YOU CAN FIND MORE INFORMATION
 
We file annual, quarterly and other reports, proxy statements and other information with the SEC.  Our SEC filings are available to the public over the Internet at the SEC’s website at http://www.sec.gov.  You may also read and copy any document we file at the SEC’s Public Reference Room at 100 F Street, NE, Washington, D.C. 20549.  Please call the SEC at 1-800-SEC-0330 for further information on the Public Reference Room.  Our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, and Current Reports on Form 8-K, including any amendments to those reports, and other information that we file with or furnish to the SEC pursuant to Section 13(a) or 15(d) of the Exchange Act can also be accessed free of charge through the Internet.  These filings will be available as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC.
 
We have filed with the SEC a registration statement under the Securities Act of 1933 relating to the offering of these securities. The registration statement, including the attached exhibits, contains additional relevant information about us and the securities. This prospectus does not contain all of the information set forth in the registration statement. You can obtain a copy of the registration statement, at prescribed rates, from the SEC at the address listed above. The registration statement and the documents referred to below under “Incorporation by Reference” are also available on our Internet website, www.pacificbiosciences.com. We have not incorporated by reference into this prospectus the information on our website, and you should not consider it to be a part of this prospectus.

-32-

Table of Contents
INFORMATION INCORPORATED BY REFERENCE
 
The SEC allows us to incorporate by reference into this prospectus certain information we file with it, which means that we can disclose important information by referring you to those documents.  The information incorporated by reference is considered to be a part of this prospectus, and information that we file later with the SEC will automatically update and supersede information contained in this prospectus and any accompanying prospectus supplement.  We incorporate by reference the documents listed below that we have previously filed with the SEC (excluding any portions of any Form 8-K that are not deemed “filed” pursuant to the General Instructions of Form 8-K):
 
 	●	Annual Report on Form 10-K for the fiscal year ended December 31, 2012, including the information specifically incorporated by reference into the Form 10-K from our definitive proxy statement for our 2013 Annual Meeting of Stockholders;	
 
 	●	Quarterly Report on Form 10-Q for the three months ended March 31, 2013; and	
 
 	●	Current Reports on Form 8-K filed on January 25, 2013, February 19, 2013, April 17, 2013 and April 24, 2013.	
 
We also incorporate by reference into this prospectus additional documents that we may file with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the completion or termination of the offering, including all such documents we may file with the SEC after the date of the initial registration statement and prior to the effectiveness of the registration statement, but excluding any information deemed furnished and not filed with the SEC.  Any statements contained in a previously filed document incorporated by reference into this prospectus is deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus, or in a subsequently filed document also incorporated by reference herein, modifies or supersedes that statement.
 
This prospectus may contain information that updates, modifies or is contrary to information in one or more of the documents incorporated by reference in this prospectus. You should rely only on the information incorporated by reference or provided in this prospectus. We have not authorized anyone else to provide you with different information. You should not assume that the information in this prospectus is accurate as of any date other than the date of this prospectus or the date of the documents incorporated by reference in this prospectus.
 
We will provide to each person, including any beneficial owner, to whom this prospectus is delivered, upon written or oral request, at no cost to the requester, a copy of any and all of the information that is incorporated by reference in this prospectus.
 
Requests for such documents should be directed to:
 
Active Power, Inc.	
2128 W. Braker Lane, BK 12,	
Austin, Texas  78758	
Attn: Investor Relations	
 
You may also access the documents incorporated by reference in this prospectus through our website at www.activepower.com. Except for the specific incorporated documents listed above, no information available on or through our website shall be deemed to be incorporated in this prospectus or the registration statement of which it forms a part.

-33-

Table of Contents
 
$50,000,000

Common Stock
 
Preferred Stock
 
Depositary Shares
 
Warrants
 
Debt Securities
 
Units
 
PROSPECTUS
 
June 26, 2013