<PAGE>

  As filed with the Securities and Exchange Commission on September 15, 1999

                                       Registration Statement No. 333-__________

================================================================================

                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549
                            ______________________

                                   FORM S-3
                            ______________________

            REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                            ______________________

                         SATCON TECHNOLOGY CORPORATION
            (Exact name of registrant as specified in its charter)
                            ______________________

         DELAWARE                                           04-2857552
  (State or other jurisdiction           (I.R.S. Employer Identification No.)
of incorporation or organization)

                               161 First Street
                     Cambridge, Massachusetts  02142-1221
                                (617) 661-0540
                       (Address, including zip code, and
                    telephone number, including area code,
                           of registrant's principal
                              executive offices)
                            ______________________

                              David B. Eisenhaure
         President, Chief Executive Officer and Chairman of the Board
                         SatCon Technology Corporation
                               161 First Street
                     Cambridge, Massachusetts  02142-1221
                                (617) 661-0540
                    (Name, address, including zip code, and
                    telephone number, including area code,
                             of agent for service)

                                   Copy to:

                             Jeffrey N. Carp, Esq.
                               HALE AND DORR LLP
                                60 State Street
                          Boston, Massachusetts 02109
                                (617) 526-6000

     Approximate date of commencement of proposed sale to public:  As soon as
practicable after this Registration Statement becomes effective.

     If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box. [_]

     If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box. [X]

     If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering. [_] 333-_______.

     If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [_] 333-__________.

     If delivery of the Prospectus is expected to be made pursuant to Rule 434,
please check the following box. [_]

                        _______________________________

                        CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------------
           Title of Shares to be Registered         Amount        Proposed        Proposed          Amount of
                                                     to be        Maximum         Maximum        Registration Fee
                                                   Registered   Offering Price    Aggregate
                                                                  Per Share     Offering Price
-------------------------------------------------------------------------------------------------------------------
<S>                                                <C>          <C>             <C>              <C>
Common Stock, $.01 par value per share...........  2,396,690(1)     $8.8438(2)     $21,195,848(2)   $5,893
-------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)  Consists of (i) 1,230,770 shares of Common Stock issuable upon conversion
     of shares of Preferred Stock at a conversion price of $7.80 per share; (ii)
     810,000 shares of Common Stock issuable upon exercise of warrants at an
     exercise price of $8.54 per share; (iii) 120,000 shares of Common Stock
     issuable upon exercise of a warrant at an exercise price of $7.80 per
     share; (iv) 68,795 shares of Common Stock issuable upon exercise of
     warrants at an exercise price of $10.61 per share; (v) 67,125 shares of
     Common Stock issuable upon exercise of warrants at an exercise price of
     $11.43 per share; (vi) 50,000 shares of Common Stock issuable upon exercise
     of a non-qualified stock option at an exercise price of $5.75 per share;
     and (vii) 50,000 shares of Common Stock issuable upon exercise of a non-
     qualified stock option at an exercise price of $6.75 per share.

(2)  Estimated solely for purposes of calculating the registration fee pursuant
     to Rule 457(c) under the Securities Act and based upon the average of the
     high and low prices on the Nasdaq National Market on September 14, 1999.

                       _________________________________

     The Company hereby amends this Registration Statement on such date or dates
as may be necessary to delay its effective date until the Company shall file a
further amendment which specifically states that this Registration Statement
shall thereafter become effective in accordance with Section 8(a) of the
Securities Act of 1933 or until the Registration Statement shall become
effective on such date as the Commission, acting pursuant to said Section 8(a),
shall determine.

================================================================================
<PAGE>

     The information in this prospectus is not complete and may be changed.
These securities may not be sold until the registration statement filed with the
Securities and Exchange Commission is effective. This prospectus is not an offer
to sell these securities and it is not soliciting an offer to buy these
securities in any state where the offer or sale is not permitted.


                Subject to completion, dated September 15, 1999

PROSPECTUS
                         SATCON TECHNOLOGY CORPORATION

                       2,396,690 SHARES OF COMMON STOCK
                          ___________________________

     In August 1999, in connection with a private financing, we issued shares of
preferred stock convertible into an aggregate of 1,025,641 shares of our common
stock. In that financing, we also issued warrants to purchase an aggregate of
675,000 shares of our common stock. The conversion price of the preferred stock
is $7.80 per share, subject to adjustment for stock splits, similar events and
certain issuances of common stock below the conversion price, and the exercise
price of the warrants is $8.54 per share, subject to adjustment for stock splits
and similar events. The warrants expire on August 25, 2003. The shares covered
by this Prospectus also include 340,129 shares issuable to the investors in the
private financing in the event of certain adjustments. In connection with the
offering, we also issued a warrant to a placement agent to purchase 120,000
shares of our common stock, as adjusted for stock splits and similar events, at
an exercise price of $7.80 per share. This warrant expires on August 25, 2003.
This prospectus relates to the public offering, which will not be underwritten,
of the shares issuable to the investors in the private financing upon conversion
of the preferred stock and exercise of the warrants and the shares issuable to
the placement agent upon exercise of its warrant.

     In April 1999, we issued non-qualified stock options to purchase an
aggregate of 100,000 shares of our common stock to a consulting firm in
consideration for services rendered to us by that firm. Upon exercise of these
options, we are obligated to issue to that firm 50,000 shares of our common
stock at an exercise price of $5.75 per share and 50,000 shares of our common
stock at an exercise price of $6.75 per share. The options expire one year after
the effective date of the registration statement of which this prospectus is a
part. This prospectus also relates to the public offering, which will not be
underwritten, of the shares issuable upon exercise of these options.

     In addition, we previously issued warrants to purchase shares of our common
stock to certain individuals and entities. Upon exercise of these warrants, we
are obligated to issue 68,795 shares of our common stock to warrantholders at an
exercise price of $10.61 per share and 67,125 shares of our common stock to
other warrantholders at an exercise price of $11.43 per share, subject to
adjustment for stock splits and similar events. These warrants expire at 5:00
p.m., Boston, Massachusetts time, on November 11, 1999. This prospectus also
relates to the public offering, which will not be underwritten, of the shares
issuable upon exercise of these warrants.

     We will not receive any of the proceeds from the sale of the shares. We
will, however, receive the exercise price of the warrants and options, in the
amounts indicated above.

     We have agreed to pay certain expenses in connection with the registration
of the shares and to indemnify the selling stockholders against certain
liabilities.  The selling stockholders will pay all underwriting discounts and
selling commissions, if any, in connection with the sale of the shares.

     The selling stockholders, or their pledgees, donees, transferees or other
successors in interest, may offer the shares through public or private
transactions at prevailing market prices, at prices related to prevailing market
prices or at privately negotiated prices.

     Our common stock is traded on the Nasdaq National Market under the symbol
"SATC."  On September 14, 1999, the closing sale price of the common stock on
Nasdaq was $8.9375 per share.
                          ___________________________

     The securities offered hereby involve a high degree of risk.  See "Risk
Factors" beginning on page 6.
                          ___________________________

The Securities and Exchange Commission and state securities regulators have not
approved or disapproved of these securities or determined whether this
prospectus is truthful or complete.  Any representation to the contrary is a
criminal offense.

                          ___________________________

               The date of this prospectus is September __, 1999.
<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                               Page
                                                                                               ----
<S>                                                                                            <C>
Where to Find More Information............................................................        4

Incorporation of Certain Documents by Reference...........................................        4

Special Note Regarding Forward-Looking Information........................................        5

Summary Description of Our Business.......................................................        6

Risk Factors..............................................................................        6

Use of Proceeds...........................................................................       15

Selling Stockholders......................................................................       16

Description of Capital Stock..............................................................       17

Plan of Distribution......................................................................       19

Legal Matters.............................................................................       20

Experts...................................................................................       20
</TABLE>

                          ___________________________

     We have not authorized anyone to provide you with information different
from that contained or incorporated by reference in this prospectus.  The
selling stockholders are offering to sell, and seeking offers to buy, shares of
our common stock only in jurisdictions where offers and sales are permitted.
The information contained in this prospectus is accurate only as of the date of
this prospectus, regardless of the time of delivery of this prospectus or of any
sale of common stock.

                                      -3-
<PAGE>

                        WHERE TO FIND MORE INFORMATION

     We file annual, quarterly, and current reports, proxy statements and other
documents with the Securities and Exchange Commission.  You may read and copy
any document we file at the SEC's public reference room at Judiciary Plaza
Building, 450 Fifth Street, N.W., Room 1024, Washington, D.C. 20549.  You should
call 1-800-SEC-0330 for more information on the public reference room.  Our SEC
filings are also available to you on the SEC's Internet site at
http://www.sec.gov.  Our common stock is quoted on Nasdaq.

     This prospectus is part of a registration statement that we filed with the
SEC.  The registration statement contains more information than this prospectus
regarding us and our common stock, including certain exhibits and schedules.
You can obtain a copy of the registration statement from the SEC at the address
listed above or from its Internet site.


                INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

     The SEC allows us to "incorporate" into this prospectus information we file
with the SEC in other documents.  This means that we can disclose important
information to you by referring to other documents that contain that
information.  The information incorporated by reference is considered to be part
of this prospectus.  Information contained in this prospectus and information
that we file with the SEC in the future and incorporate by reference in this
prospectus automatically updates and supersedes previously filed information.
We incorporate by reference the documents listed below and any future filings we
make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities
Exchange Act of 1934 prior to the sale of all the shares covered by this
prospectus.

     The following documents that we have filed with the SEC are incorporated
herein by reference:

     (i)    Our Annual Report on Form 10-K for the year ended September 30,
            1998;

     (ii)   Our Quarterly Report on Form 10-Q for the quarter ended December 31,
            1998;

     (iii)  Our Current Report on Form 8-K dated January 4, 1999;

     (iv)   Amendment No. 1 to our Quarterly Report on Form 10-Q for the quarter
            ended March 31, 1998;

     (v)    Amendment No. 1 to our Quarterly Report on Form 10-Q for the quarter
            ended June 30, 1998;

     (vi)   Our Quarterly Report on Form 10-Q for the quarter ended March 31,
            1999;

     (vii)  Our Current Report on Form 8-K dated May 12, 1999;

     (viii) Our Current Report on Form 8-K dated May 25, 1999;

     (ix)   Our Quarterly Report on Form 10-Q for the quarter ended June 30,
            1999;

     (x)    Amendment No. 1 to our Quarterly Report on Form 10-Q for the quarter
            ended December 31, 1998;

     (xi)   Amendment No. 1 to our Quarterly Report on Form 10-Q for the quarter
            ended March 31, 1999;

     (xii)  Our Current Report on Form 8-K dated August 25, 1999;

     (xiii) All of our filings pursuant to the Exchange Act after the date of
            filing the initial registration statement and prior to effectiveness
            of the registration statement; and

                                      -4-
<PAGE>

     (xiv)  The description of our common stock contained in our Registration
            Statement on Form 8-A, including any amendments or reports filed for
            the purpose of updating that description.

You may request a copy of these documents, which will be provided to you at no
cost, by writing to:

     SatCon Technology Corporation
     161 First Street
     Cambridge, Massachusetts  02142-1221
     Attention:  Investor Relations Department
     Telephone:  (617) 661-0540


              SPECIAL NOTE REGARDING FORWARD-LOOKING INFORMATION

     This prospectus contains or incorporates 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.  You can identify these forward-looking
statements by our use of the words "believes," "anticipates," "plans,"
"expects," "may," "will," "intends," "estimates" and similar expressions,
whether in the negative or affirmative.  Although we believe that these forward-
looking statements reasonably reflect our plans, intentions and expectations, we
cannot guarantee that we actually will achieve these plans, intentions or
expectations.  Our actual results could differ materially from the plans,
intentions and expectations disclosed in the forward-looking statements we make.
We have included important factors in the cautionary statements below
(particularly under the heading "Risk Factors") that we believe could cause our
actual results to differ materially from the forward-looking statements that we
make.  We do not intend to update information contained in any forward-looking
statement we make.

                                      -5-
<PAGE>

                      SUMMARY DESCRIPTION OF OUR BUSINESS

     We were organized as a Massachusetts corporation in February 1985 and
reincorporated in Delaware in 1992.  We design, develop and manufacture
intelligent, electro-mechanical products for aerospace, transportation,
industrial and utility applications.  We also design, develop and manufacture
power and energy management products for telecommunications, silicon wafer
manufacturing, factory automation, aircraft and automotive applications.  Our
electro-mechanical products are being developed for a wide variety of U.S.
government and commercial markets.  For the government, our electro-mechanical
systems provide for applications ranging from satellite attitude control to high
speed drives for shipboard systems.  In the transportation segment, we are
developing electric and hybrid electric drive components, auxiliary power units
and advanced steering, alternator and starter/generator systems.  We are working
with major equipment producers to develop process equipment drives, high speed
and precision machine tools, manipulators and machinery isolation equipment.
Our electro-mechanical systems may offer advantages to the utility industry in
power generation, energy storage and power quality.  In the consumer market, we
are developing variable speed motors for refrigeration equipment and other long-
life, high-efficiency machinery.

     Our executive offices are located at 161 First Street, Cambridge,
Massachusetts 02142-1221 and our telephone number is (617) 661-0540.  Our
Internet home page is located at http://www.satcon.com.  The information on our
Internet website is not incorporated by reference in this prospectus.  We own
various trademark rights and hold federal trademark registrations for our name
and the SatCon logo.  "SatCon Technology Corporation," "SatCon," "Active Motion
Control," and "Technology For A World In Motion" are registered trademarks of
SatCon.  This prospectus also includes or incorporates by reference names and
marks of companies other than ours.


                                 RISK FACTORS

     You should carefully consider the risks described below before making an
investment decision.  The risks and uncertainties described below are not the
only ones facing our company.  Additional risks and uncertainties not presently
known to us or that we currently deem immaterial may also impair our business
operations.

     If any of the following risks actually occur, our business, financial
condition or results of operations could be materially adversely affected.  In
such case, the trading price of our common stock could decline and you may lose
all or part of your investment.

     We cannot assure market acceptance or commercial viability of our products

     We intend to continue to expand development of our technologies for use in
commercial business applications.  However, we cannot assure that our planned
commercial products will realize market acceptance, that they will meet the
technical demands of potential customers or that they will offer cost-effective
advantages over our competitors' products.  Our commercial marketing efforts to
date involve development contracts with several customers, identification of
specific market segments for active motion control and power and energy
management systems and the continuation of marketing efforts of recently
acquired businesses.  We cannot know if our commercial marketing efforts will be
successful in the future.  Furthermore, we cannot assure that our technologies,
in their current form, will be suitable for specific commercial applications or
that further design modifications, beyond anticipated changes to accommodate
different markets, will not be necessary.

     We may not be able to develop or sell our products under development

     We have a number of potential products under development.  We face many
technological challenges that we must successfully address to complete any of
our development efforts.  Our product development involves a high degree of risk
and may require significant capital resources to develop.  Returns to our
investors are dependent upon successful development and commercialization of
these products.  For example, the successful development of a terrestrial
flywheel energy storage system for an uninterruptible power supply by Beacon
Power Corporation, an

                                      -6-
<PAGE>

affiliate of SatCon, involves significant technological challenges. It has and
will continue to require significant investment in research and development
before SatCon and Beacon can determine whether the development of Beacon's
technology was successful and whether the resulting products will be
commercially viable and accepted by the marketplace. Many proposed products
based on our technologies will require significant additional expenditures for
research and development. We cannot assure that any of the products we are
developing, or those that we develop in the future, will be technologically
feasible or accepted by the marketplace. Also, we cannot assure that any of our
product development will be completed in any particular time-frame.

     We have several government contracts, and the loss of these contracts could
adversely affect our financial condition and results of operations

     Although we have been developing applications of our technology for both
commercial and government markets, a large percentage of our revenue is from
Department of Defense and NASA contracts, subcontracts and grants.  The majority
of these contracts were awarded through the Small Business Innovation Research
Program.  Although we believe that the majority of our revenues in the future
will result from commercial applications of our technologies, a significant
portion of our business in the next few years will likely continue to involve
research and development for the U.S. Government and its agencies.
Consequently, a portion of future revenues may be subject to funding approval
from Congress, which involves political, budgetary and other considerations over
which we have no control.  To date, we have not been adversely affected by
reductions in defense spending.  We believe that government funding for areas of
our research and development activities will continue without reduction.
However, we cannot assure that this funding will not be reduced in the future.
Any reduction could materially adversely affect our business.  In addition, many
of our U.S. Government contracts may be cancelled at any time by the U.S.
Government with limited or no penalty.

     We anticipate seeking significant contracts with commercial customers.  We
cannot assure that we will succeed in receiving additional commercial contracts
or that such contracts, if awarded, will not be cancelled.  As with the
government contracts, the cancellation of any of these contracts could have a
material adverse effect on us.

     We lack significant revenues and have recent and anticipated negative cash
flow and operating losses

     We have achieved limited profitability in each of our fiscal years ended
September 30, 1994, 1993, 1992 and 1991, and we recorded a loss for the fiscal
years ended September 30, 1998, 1997, 1996 and 1995.  For the nine months ended
June 30, 1999, we had a net operating loss of $9.8 million and negative cash
flows from operating activities of $3 million.  In order to achieve
profitability, we must successfully achieve all or some combination of the
following:

     .    develop new products for our existing markets,
     .    sell these products to existing and new customers,
     .    increase gross margins through higher volumes and manufacturing
          efficiencies,
     .    control our operating expenses, and
     .    develop and manage our distribution capability.

If our revenue does not increase significantly or the increase in our expenses
is greater than expected, we may not achieve or sustain profitability or
generate positive cash flow in the future.  We cannot assure that we will
accomplish these objectives or be profitable in the future.

                                      -7-
<PAGE>

     Our acquisition strategy involves several risks

     A component of our business strategy is to seek the acquisition of
businesses, products and technologies that complement or augment our existing
businesses, products and technologies. For example, in January 1997, we acquired
K&D MagMotor Corp., a manufacturer of custom electric motors targeting the
factory automation, medical, semi-conductor and packaging markets. In April
1997, we acquired substantially all of the assets of Film Microelectronics,
Inc., a manufacturer and producer of custom integrated circuits for the
communications, industrial, military and aerospace markets. In January 1999, we
acquired Inductive Components, Inc. (a value-added supplier of systems in the
machine tool and semiconductor industry) and Lighthouse Software, Inc. (which
designs and develops software for the industrial machine tool industry). In
April 1999, we also acquired HyComp, Inc., a manufacturer of high-performance,
high-quality, multi-chip modules.

     Acquisitions are difficult to identify and complete for a number of
reasons, including competition among prospective buyers and the need for
regulatory approvals, including antitrust approvals. We cannot assure that we
will be able to successfully identify acquisition candidates or complete future
acquisitions or that we will be able to successfully integrate any of the
acquired businesses into our operations.

     In order to finance acquisitions, we may have to raise additional funds
through public or private financing. Any equity or debt financing, if available
at all, may be on terms which are not favorable to us and, in the case of equity
financing, may result in dilution to our stockholders. We cannot assure that we
will be able to operate acquired businesses profitably or otherwise implement
our growth strategy successfully. The successful combination of companies in a
rapidly changing high technology industry such as ours may be more difficult to
accomplish than in other industries. Our ability to integrate any newly acquired
entities will require us to continue to improve our operational, financial and
management information systems, and to motivate and effectively manage our
employees. If our management is unable to manage growth effectively, the quality
of our products, our ability to identify, hire and retain key personnel and our
results of operations could be materially and adversely affected.

     If we experienced a period of significant growth or expansion, it would
place a strain on our resources

     Rapid growth of our business, of which there can be no assurance, may
strain our management, operational and technical resources. If we are successful
in obtaining rapid market penetration of our products, we will be required to
deliver large volumes of quality products or components to our customers and
licensees on a timely basis at a reasonable cost to us. We have limited
experience in delivering large volumes of our products and have limited capacity
to meet wide-scale production requirements. We cannot assure that our efforts to
expand our manufacturing and quality assurance activities will be successful or
that we will be able to satisfy large-scale commercial production on a timely
and cost-effective basis. Our success will also depend, in part, upon our
ability to modify our technology and products to meet end-user requirements.
Also, we will be required to continue to improve our operational, management and
financial systems and controls to meet anticipated growth. Failure to manage
growth would have a material adverse effect on our business.

     Because our expenses are largely fixed, an unexpected revenue shortfall may
adversely affect our business

     Our expense levels are based primarily on our estimates of future revenues
and are largely fixed. A large portion of our expense relates to headcount that
cannot be easily reduced without adversely affecting our business. We may be
unable to adjust spending rapidly enough to compensate for any unexpected
revenue shortfall. Accordingly, any significant shortfall in revenues in
relation to our planned expenditures would reduce, and possibly eliminate, any
operating income and could materially adversely affect our business, operating
results and financial condition.

                                      -8-
<PAGE>

     Our business could be adversely affected if we are unable to protect our
patents and proprietary technology

     We currently own United States patents which expire between 2008 and 2017.
We also have patent applications pending with the U.S. Patent and Trademark
Office. As a qualifying small business, we have retained commercial ownership
rights to proprietary technology developed under various U.S. Government
contracts and grants, including SBIR contracts. Our patent and trade secret
rights are of material importance to us and to our future prospects. No
assurance can be given as to the issuance of additional patents or, if so
issued, as to their scope. Patents granted may not provide meaningful protection
from competitors. Even if a competitor's products were to infringe patents owned
by us, it would be costly for us to pursue our rights in an enforcement action
and would divert funds and resources which otherwise could be used in our
operations. Furthermore, there can be no assurance that we would be successful
in enforcing intellectual property rights or that we may not infringe patent or
intellectual property rights of third parties. However, to date, we have not
been required to defend our patents or proprietary information against claims by
third parties.

     Since we intend to enforce our patents, trademarks and copyrights and
protect our trade secrets, we may be involved from time to time in litigation to
determine the enforceability, scope and validity of these rights.  This
litigation could result in substantial costs to us and divert efforts by our
management and technical personnel.

     In addition to our patent rights, we also rely on treatment of our
technology as trade secrets and upon confidentiality agreements, which all of
our employees are required to sign, assigning to us all patent rights and
technical or other information developed by the employees during their
employment with us.  Our employees have also agreed not to disclose any trade
secrets or confidential information without our prior written consent.
Notwithstanding these confidentiality agreements, there can be no assurances
that other companies will not require information which we consider to be
proprietary.

     Our products, systems and sales may be subject to Year 2000 problems

     We have assessed our software systems and internal operations.  We believe
we have resolved all potential Year 2000 issues or problems and, to the best of
our knowledge, our systems are Year 2000 compliant.  However, if our systems do
not operate properly with respect to date calculations involving the Year 2000
and subsequent dates, we could incur unanticipated expenses to remedy any
problems, which could seriously harm our business.  We may also experience
reduced sales of our products as current or potential customers reduce their
budgets due to increased expenditures on their own Year 2000 compliance efforts.

     Additionally, we rely on information technology supplied by third parties
and our other business partners, including third-party distributors and
consultants, who are also heavily dependent on information technology systems
and on their own and third-party vendor systems. Year 2000 problems experienced
by us or any of these third parties could materially adversely affect our
business. Prior versions of our products may contain technology from third
parties that is not Year 2000 compliant.

     Given the pervasive nature of the Year 2000 problem, we cannot guarantee
that disruptions in other industries and market segments will not adversely
affect our business.  Moreover, our costs related to Year 2000 compliance, which
thus far have not been material, could ultimately be significant.  In the event
that we experience unforeseen disruptions as a result of the Year 2000 problem,
our business could be seriously affected.

                                      -9-
<PAGE>

     There is intense competition in our industry

     A variety of companies compete in each of the areas in which we are
developing and selling products.  To date, we have faced only limited
competition in providing research services, prototype development and custom and
limited quantity manufacturing.  We expect competition to intensify greatly as
commercial applications increase for our products under development.  Some of
our competitors are well established and have substantial managerial, technical,
financial, marketing and product development resources competitive with, and, in
the some instances, greater than ours.  Additional companies, both large and
small, are entering the markets in which we compete.  There can also be no
assurance that current and future competitors will not develop new or enhanced
technologies perceived to be superior to those sold or developed by us.  There
can be no assurance that we will be successful in such a competitive
environment.

     Competition for personnel in our industry is intense

     Our success will depend, in large part, upon our ability to attract,
motivate and retain highly qualified scientists and engineers, as well as highly
skilled and experienced management and technical personnel.  Competition for
these personnel is intense, and there can be no assurance that we will be
successful in attracting, motivating or retaining key personnel.  Our success
depends to a significant extent upon a number of key employees, including
members of senior management.  The loss of the services of one or more of these
key employees could have a material adverse effect on SatCon.

     Our business is dependent on our founder and chief executive officer

     We are particularly dependent upon the services of David B. Eisenhaure, our
President, Chief Executive Officer, Chairman of the Board and founder.  The loss
of Mr. Eisenhaure's services would have a material adverse effect on our
business and results of operations, including our ability to attract employees
and secure and complete additional work.

     Our business could be subject to product liability claims

     Our business exposes us to potential product liability claims which are
inherent in the manufacturing, marketing and sale of electro-mechanical
products, and as such, we may face substantial liability for damages resulting
from the faulty design or manufacture of products or improper use of products by
end-users.  We currently maintain a low level of product liability insurance,
and there can be no assurance that this insurance will provide sufficient
coverage in the event of a claim.  Also, we cannot predict whether we will be
able to maintain such coverage on acceptable terms, if at all, or that a product
liability claim would not materially adversely affect our business or financial
condition.

     Our business is under the significant control of our directors and officers

     Our officers and directors, and their affiliates, beneficially own
approximately 43.3% of our outstanding common stock, of which approximately
32.0% of the outstanding common stock is held by Mr. Eisenhaure, our President,
Chief Executive Officer and Chairman of the Board of Directors.  As a practical
matter, Mr. Eisenhaure may have the ability to elect our directors and to
determine the outcome of corporate actions requiring stockholder approval,
irrespective of how our other stockholders may vote.  This concentration of
ownership may have the effect of delaying or preventing a change in control of
SatCon.

                                      -10-
<PAGE>

     Our share price could be subject to extreme price fluctuations, and you
could have difficulty trading your shares

     The markets for equity securities in general, and for those of high
technology companies in particular, have been volatile and the market price of
our common stock, which is traded on the Nasdaq National Market under the symbol
SATC, may be subject to significant fluctuations.  This could be in response to
operating results, announcements of technological innovations or new products by
us or our competitors, patent or proprietary rights developments and market
conditions for high technology stocks in general.  In addition, the stock market
in recent years has experienced extreme price and volume fluctuations that often
have been unrelated or disproportionate to the operating performance of
individual companies.  These market fluctuations, as well as general economic
conditions, may adversely affect the market price of the common stock.  The
trading prices of the stocks of many high technology companies are at or near
their historical highs and reflect price/earnings ratios substantially above
historical norms.  There can be no assurance that the trading price of our
common stock will remain at or near its current level.

     We could experience fluctuations in our quarterly performance

     Our quarterly operating results may vary significantly depending on a
number of factors, including:

     .    the number of contracts, subcontracts and orders we are able to
          obtain,
     .    the amount of revenues generated from such contracts, subcontracts and
          orders,
     .    the level of research and development expenses incurred by us and our
          subsidiaries which go unreimbursed,
     .    the size, timing and shipment of orders from our subsidiaries, and
     .    general economic conditions.

Because our operating expenses are based on anticipated revenue levels, our
sales cycle for development work is relatively long and a high percentage of our
expenses are fixed for the short term, a small variation in the timing of
recognition of revenue can cause significant variations in operating results
from quarter to quarter.

     General economic conditions may affect investors' expectations regarding
our financial performance and adversely affect our stock price

     Certain industries in which we sell products, such as the semiconductor
industry, are highly cyclical.  In the future, our results may be subject to
substantial period-to-period fluctuations as a consequence of the industry
patterns of our customers, general or regional economic conditions and other
factors.  These factors may also have a material adverse effect on our business,
operating results and financial condition.

     Rapid technological change could render our products obsolete

     Our markets are characterized by rapid technological change, frequent new
product introductions and enhancements, uncertain product life cycles, changes
in customer requirements and evolving industry standards.  The introduction of
new products embodying new technologies and the emergence of shifting customer
demands or changing industry standards could render our existing products
obsolete and unmarketable which would have a material adverse effect on our
business, operating results and financial condition.  Our future success will
depend upon our ability to continue to develop and introduce a variety of new
products and product enhancements to address the increasingly sophisticated
needs of our customers.  This will require us to continue to make substantial
product development investments.  We may experience delays in releasing new
products and product enhancements in the future.  Material delays in introducing
new products or product enhancements may cause customers to forego purchases of
our products and purchase those of our competitors.

                                      -11-
<PAGE>

     We may issue preferred stock which could affect the rights and value of
our common stock

     We are authorized to issue up to 1,000,000 shares of preferred stock, 8,000
shares of which are represented by Series A Convertible Redeemable Preferred
Stock which are issued and outstanding.  The preferred stock may be issued in
one or more series, the terms of which may be determined at the time of issuance
by our board of directors, without further action by stockholders and may
include voting rights (including the right to vote as a series on particular
matters), preferences as to dividends and liquidation, conversion and redemption
rights and sinking fund provisions.  Other than the series A preferred stock, no
preferred stock is currently outstanding, and we have no present plans to issue
any additional preferred stock.  However, the issuance of any additional
preferred stock could affect the rights of the holders of common stock, thereby
reducing the value of our common stock.  In particular, specific rights granted
to future holders of preferred stock could be used to restrict our ability to
obtain financing for future operations or to merge with or sell our assets to a
third party, thereby preserving control of SatCon by our present equity holders
and preventing you from realizing a premium on your shares.  Thus, the issuance
of preferred stock could adversely affect your voting power.  See "Description
of Capital Stock -- Preferred Stock."

     We are required to redeem the Preferred Stock or reset the conversion price
in certain circumstances

     If it has not been converted to common stock prior to that time, we are
required to redeem the series A preferred stock in August 2006 at a price equal
to its liquidation preference.  If the average market price of the common Stock
(after adjustments for stock splits, reclassifications and similar transactions)
is $5.00 or less, for the sixty trading days prior to August 25, 2003, we are
required to redeem the series A preferred stock in August 2003 at a price equal
to its liquidation value.  The redemption price may be paid, at our option, in
cash and/or shares of common stock.

     The series A preferred stock is initially convertible into common stock at
a conversion price of $7.80 per share.  The conversion price and the number of
shares of our common stock issuable upon conversion are subject to adjustment in
certain circumstances, including issuances, subject to certain exceptions, of
common stock below the initial conversion price.  The holders of the series A
preferred stock have the right in August 2000 to reset the conversion price to
the greater of the then current market price and $5.00 per share.  However, if
the common stock trades for 20 consecutive trading days at a price of $11.70 or
higher, or if we complete a specific financing transaction, this reset right
terminates.

     We could issue additional common stock, which might dilute the value of our
common stock

     We have authorized 20,000,000 shares of common stock, of which 9,617,009
shares are issued and outstanding as of September 13, 1999.  Our board of
directors has the authority, without action or vote of the stockholders, to
issue all or part of the authorized but unissued shares.  This issuance would
dilute your percentage ownership interest and might dilute the book value of our
common stock.  See "Description of Capital Stock -- Common Stock."

     Common stock investors may be diluted by the exercise of options and
warrants, conversion of preferred stock or exercise of put rights with respect
to Beacon Power Corporation

     We have reserved 3,050,000 shares of common stock for issuance under our
stock incentive plans.  As of August 31, 1999, options to purchase an aggregate
of 1,296,329 shares of common stock are outstanding under our stock incentive
plans.  Warrants and non-qualified stock options granted outside of our stock
incentive plans to purchase 1,130,920 shares of common stock, including the
warrants exercisable for the common stock offered by this prospectus, are
outstanding.  We have also reserved 1,230,770 shares of common stock for
issuance upon conversion of the outstanding series A preferred stock.  On
October 23, 1998, we granted the purchasers of Beacon Power Corporation's Class
D Preferred Stock the right to cause us, under the circumstances described
below, to purchase all of Beacon's shares issued to those purchasers and, upon
exercise of this "put right," we must pay $4,750,000 in common stock, valued at
the average fair market value for the fifteen trading days before and after
notice of exercise of the put right.  The put right is exercisable within sixty
days of the second, third, fourth and fifth anniversary of the closing date of
that transaction, upon certain events of bankruptcy of Beacon and upon the
occurrence of certain going private transactions involving us.  The exercise of
options and

                                      -12-
<PAGE>

warrants, the conversion of preferred stock or the exercise of the put right,
and subsequent sale of the underlying common stock in the public market, could
adversely affect the market price of our common stock and prove to be a
hindrance to our future financing. Our series A preferred stock and some of our
outstanding warrants include anti-dilution provisions, including, in some cases,
adjustments to the applicable conversion price or exercise price in the event we
issue common stock at a price less than the conversion price or exercise price
then in effect. This would increase the dilutive impact of future equity
offerings at prices less than the conversion price or exercise price of the
outstanding preferred stock and certain of the warrants.

     Sales of common stock pursuant to Rule 144 may have a depressive effect on
the market price of the common stock

     Of the 9,617,009 shares issued and outstanding as of September 13, 1999,
5,775,625 shares of common stock currently outstanding are freely tradable
securities.  Other securities, such as the common stock issuable upon conversion
of the series A preferred stock or exercise of the warrants, are not considered
outstanding, but upon conversion or exercise will be entitled to be sold
pursuant to this prospectus or another registration statement and thereafter
will be freely tradeable.  Holders of 2,056,561 shares of common stock or common
stock issuable upon such conversion or exercise are entitled to such
registration rights.  Many of the other currently outstanding shares of common
stock are "restricted securities" as that term is defined under Rule 144 of the
Securities Act.  Ordinarily, under Rule 144, a person holding restricted
securities for a period of one year may, every three months, sell in ordinary
brokerage transactions or in transactions directly with a market maker an amount
equal to the greater of one percent of the company's then outstanding common
stock or the average weekly trading volume during the four calendar weeks prior
to such sale.  Sales of common stock pursuant to Rule 144 may have a depressive
effect on the market price of our common stock.  Rule 144 also permits sales by
a person who is not an affiliate of the Company (such as Duquesne Enterprises)
and who has satisfied a two-year holding period without volume limitations.

                                      -13-
<PAGE>

     We may need additional financing for our future capital needs.

     If we are unable to increase our revenues and achieve positive cash flow,
we will need to raise additional funds.  We may also need additional financing
if we:

 .    need additional cash to fund research and development costs of products
     currently under development,
 .    decide to expand faster than currently planned,
 .    develop new or enhanced services or products ahead of schedule,
 .    need to respond to competitive pressures, or
 .    decide to acquire complementary products, businesses or technologies.

     If we raise additional funds through the sale of equity or convertible debt
securities, your percentage ownership will be reduced.  In addition, these
transactions may dilute the value of the common stock outstanding.  We may have
to issue securities, such as the series A preferred stock, that may have rights,
preferences and privileges senior to our common stock.  We cannot assure you
that we will be able to raise additional funds on terms acceptable to us, if at
all.  If future financing is not available or is not available on acceptable
terms, we may not be able to fund our future needs which would have a material
adverse effect on our business, results of operations and financial condition.
We currently anticipate that the net proceeds from the series A preferred stock
offering, together with available funds, will be sufficient to meet our
anticipated needs for the reasonably foreseeable future.

     Provisions of our certificate of incorporation and bylaws and Delaware law
could deter takeover attempts

     Certain provisions of our certificate of incorporation and bylaws may
discourage, delay or prevent a change in control of SatCon that you as a
stockholder may consider favorable.  These provisions include:

 .    authorizing the issuance of "blank check" preferred stock that could be
     issued by our board of directors to increase the number of outstanding
     shares and thwart a takeover attempt,
 .    a classified board of directors with staggered, three-year terms, which may
     lengthen the time required to gain control of our board of directors,
 .    prohibiting cumulative voting in the election of directors, which would
     otherwise allow less than a majority of stockholders to elect director
     candidates, and
 .    limitations on who may call special meetings of stockholders.

     In addition, Section 203 of the Delaware General Corporation Law and
provisions in some of our stock incentive plans may discourage, delay or prevent
a change in control of our company.  In addition, as noted above, our officers
and directors beneficially own a significant percentage of our outstanding
common stock.

     We have not paid dividends since our inception

     We have not paid dividends to our stockholders since our inception and do
not anticipate paying cash dividends in the foreseeable future.  We intend to
reinvest earnings, if any, in the development and expansion of our business.
Declaration of dividends on our common stock will depend upon, among other
things, future earnings, our operating and financial condition, our capital
requirements and general business conditions.  See "Description of Capital Stock
-- Dividend Policy."



                                      -14-
<PAGE>

                               USE OF PROCEEDS

     We will not receive any proceeds from the sale of the shares by the selling
stockholders.

     We will bear all costs (excluding any underwriting discounts and
commissions and expenses incurred by the selling stockholders for brokerage,
accounting, tax or legal services or any other expenses incurred by the selling
stockholders in disposing of the shares), fees and expenses incurred in
effecting the registration of the shares covered by this prospectus, including,
without limitation, all registration and filing fees, Nasdaq listing fees, fees
and expenses of our counsel, fees and expenses of our accountants, and blue sky
fees and expenses.

                                      -15-
<PAGE>

                             SELLING STOCKHOLDERS

     The following table sets forth the number of shares owned by or issuable
upon exercise of warrants or stock options and conversion of series A preferred
stock held by each of the selling stockholders. None of the selling stockholders
has had a material relationship with SatCon or any of our subsidiaries within
the past three years other than as a result of the ownership of shares or other
securities of SatCon. No estimate can be given as to the amount of shares that
will be held by the selling stockholders after completion of this offering
because the selling stockholders may offer all or some of the shares and because
there are currently no agreements, arrangements or understandings with respect
to the sale of any of the shares. The shares offered by this prospectus may be
offered from time to time by the selling stockholders named below. The table
sets forth, to our knowledge, certain information about the selling stockholders
as of September 14, 1999.

<TABLE>
<CAPTION>
---------------------------    --------------------  ------------------  -------------------  -------------------  -----------------
Name of Selling Stockholder    Number of Shares of     Percentage of     Number of Shares of  Number of Shares of    Percentage of
                                   Common Stock       Shares of Common       Common Stock         Common Stock      Shares of Common
                                Beneficially Owned   Stock Beneficially     Offered Hereby     Beneficially Owned Stock Beneficially
                               Prior to Offering(1)    Owned Prior to                            After Offering       Owned After
                                                        Offering (1)                                 (1)(2)         Offering (1)(2)
<S>                            <C>                   <C>                 <C>                  <C>                 <C>
Brown Simpson Strategic               1,144,558           10.6%                1,144,558                   0               *
   Growth Fund, Ltd.(3)
Brown Simpson Strategic                 556,083            5.5%                  556,083                   0               *
   Growth Fund, L.P.(3)
H.C. Wainright & Co., Inc.              120,000            1.2%                  120,000                   0               *
Continental Capital &                   100,000            1.0%                  100,000                   0               *
   Equity Corporation
Dan Purjes                               34,394              *                    34,394                   0               *
Pasquale Ruggieri                        32,028              *                    32,028                   0               *
Arthur G. Jenkins                        39,168              *                    24,853              14,315               *
Matthew Balk                              7,743              *                     7,743                   0               *
Lawrence Rice                             7,239              *                     7,239                   0               *
Estate of Peter Scheib                    6,150              *                     6,150                   0               *
Charles Rodin                             5,129              *                     5,129                   0               *
Averell Satloff                           5,544              *                     4,456               1,088               *
Nicholas Moceri                           3,074              *                     3,074                   0               *
Michael Loew                              1,797              *                     1,797                   0               *
Frank Garriton                            1,656              *                     1,656                   0               *
Thomas W. Schneider                       1,602              *                     1,602                   0               *
Kevin Carey                               1,537              *                     1,537                   0               *
Joan Taylor                               1,537              *                     1,537                   0               *
Henry Tow                                 1,537              *                     1,537                   0               *
Siegfried P. Duray-Bito                     303              *                       303                   0               *
Roger P. May                                303              *                       303                   0               *
Thomas J. O'Rourke                          242              *                       242                   0               *
Paul Fitzgerald                             231              *                       231                   0               *
Jay A. Murray                               109              *                       109                   0               *
</TABLE>

__________________________
* Less than one percent of the number of shares of common stock outstanding.

(1)  Except as otherwise indicated, the number of shares beneficially owned is
     determined under rules promulgated by the SEC, and the information is not
     necessarily indicative of beneficial ownership for any other purpose.  To
     our knowledge, the selling stockholders have sole voting and investment
     power with respect to all shares listed as owned by the selling
     stockholders.

                                      -16-
<PAGE>

(2)  We do not know when or in what amounts a selling stockholder may offer
     shares for sale.  The selling stockholders may not sell any or all of the
     shares offered by this prospectus.  Because the selling stockholders may
     offer all or some of the shares pursuant to this offering, and because
     there are currently no agreements, arrangements or understandings with
     respect to the sale of any of the shares that will be held by the selling
     stockholders after completion of the offering, we can not estimate the
     number of the shares that will be held by the selling stockholders after
     completion of the offering.  However, for purposes of this table, we have
     assumed that, after completion of the offering, none of the shares covered
     by this prospectus will be held by the selling stockholders.

(3)  Does not include an aggregate of 340,129 shares of common stock issuable in
     the event of certain adjustments.


                         DESCRIPTION OF CAPITAL STOCK

Common Stock

     We are authorized to issue up to 20,000,000 shares of common stock, of
which 9,617,009 shares are currently issued and outstanding.  The following
summary description of the common stock is qualified in its entirety by
reference to our certificate of incorporation.

     The holders of common stock are entitled to one vote for each share held of
record on each matter submitted to a vote of stockholders.  There is no
cumulative voting for election of directors.  Subject to the prior rights of any
series of preferred stock which may from time to time be outstanding, holders of
common stock are entitled to receive ratably such dividends as may be declared
by the Board of Directors out of funds legally available therefor, and, upon the
liquidation, dissolution or winding up of SatCon, are entitled to share ratably
in all assets remaining after payment of liabilities and payment of accrued
dividends and liquidation preference on the preferred stock, if any.  Holders of
common stock have no preemptive rights and have no rights to convert their
common stock into any other securities.  The outstanding common stock is, and
the common stock to be outstanding upon completion of the offering will be,
validly issued, fully paid, and nonassessable.

Preferred Stock

     We are authorized to issue up to 1,000,000 shares of preferred stock.  The
preferred stock may be issued in one or more series, the terms of which may be
determined at the time of issuance by the Board of Directors, without further
action by stockholders and may include voting rights (including the right to
vote as a series on particular matters), preferences as to dividends and
liquidation, conversion, redemption rights and sinking fund provisions.  The
issuance of preferred stock could reduce the rights, including voting rights, of
the holders of common stock, and, therefore, reduce the value of our common
stock.  In particular, specific rights granted to future holders of preferred
stock could be used to restrict our ability to merge with or sell our assets to
a third party, thereby preserving control of SatCon by existing management.

Series A Convertible Redeemable Preferred Stock

     8,000 shares of our series A preferred stock were outstanding on
September 13, 1999. The series A preferred stock has a liquidation value of
$1,000 per share and is entitled to distribution upon liquidation of SatCon of
its liquidation value in priority to the common stock and any other class of
securities ranking junior to the series A preferred stock. The series A
preferred stock is initially convertible into common stock at a conversion price
of $7.80 per share. The conversion price and the number of shares issuable upon
conversion are subject to adjustment in certain circumstances, including
issuances, subject to certain exceptions, of common stock below the initial
conversion price. The holders of the series A preferred stock have the right in
August 2000 to reset the conversion price to the greater of the then current
market price and $5.00 per share. However, if the common stock trades for

                                      -17-
<PAGE>

20 consecutive trading days at a price of $11.70 or higher or if we complete a
specific financing transaction, the reset right in August 2000 terminates.

     If it has not been converted to common stock prior to that time, we are
required to redeem the series A preferred stock in August 2006 at a price equal
to its liquidation preference.  If the average market price of our common stock
(after adjustments for stock splits, reclassifications and similar transactions)
is $5.00 or less, for the sixty trading days prior to August 25, 2003, we are
required to redeem the series A preferred stock in August 2003 at a price equal
to its liquidation value.  The redemption price may be paid, at our option, in
cash and/or shares of common stock.  We also have the right to redeem the series
A preferred stock if the market value of our common stock is greater than $15.60
for twenty consecutive trading days.

     Holders of our series A preferred stock have the right to vote as a class,
as if their shares were converted into common stock, if we sell all or
substantially all of our assets or if we merge with or into another company and
we are not the surviving entity.  Moreover, without the approval of the holders
of 75% of the outstanding shares of the series A preferred stock, we cannot
amend, alter or repeal the preferences, special rights or other powers of the
series A preferred stock so as to affect adversely the series A preferred stock.

Limitation of Officers' and Directors' Liabilities Under Delaware Law

     In accordance with Delaware law, our certificate of incorporation
eliminates in certain circumstances the liability of our directors for monetary
damages for breach of their fiduciary duty as directors.  This provision does
not eliminate the liability of a director (i) for a breach of the director's
duty of loyalty to SatCon or our stockholders, (ii) for acts or omissions by the
director not in good faith or which involve intentional misconduct or a knowing
violation of law (iii) for a willful or negligent declaration of an unlawful
dividend, stock purchase or redemption or (iv) for transactions from which the
director derived an improper personal benefit.

     In addition, our bylaws include provisions to indemnify our officers and
directors and other persons against expenses, judgments, fines and amounts paid
in settlement in connection with threatened, pending or completed suits of
proceedings against such persons by reason of serving or having served as
officers, directors or in other capacities, except in relation to matters with
respect to which such persons shall be determined not to have acted in good
faith, unlawfully or in the best interests of SatCon.  With respect to matters
as to which our officers and directors and others are determined to be liable
for misconduct or negligence in the performance of their duties, our bylaws
provide for indemnification only to the extent that we determine that such
person acted in good faith and in a manner not opposed to the best interests of
SatCon.

     However, insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers, or persons controlling
SatCon pursuant to Delaware state law, as well as the foregoing charter and
bylaw provisions, we have has been informed that in the opinion of the SEC, such
indemnification as it relates to federal securities laws is against public
policy, and therefore, unenforceable.

     Further, insofar as limitation of liabilities may be so permitted pursuant
to Delaware state law, as well as the foregoing charter and bylaw provisions,
such limitation of liabilities does not apply to any liabilities arising under
federal securities laws.

Dividend Policy

     We have not paid dividends on our common stock since our inception, and we
have no intention of paying any dividends to our stockholders in the foreseeable
future.  We intend to reinvest earnings, if any, in the development and
expansion of our business.  Any declaration of dividends in the future will be
at the election of the Board of Directors and will depend upon the earnings,
capital requirements and financial position of SatCon, general economic
conditions, requirements of any bank lending arrangements which may then be in
place and other pertinent factors.

                                      -18-
<PAGE>

                              PLAN OF DISTRIBUTION

     The shares covered by this prospectus may be offered and sold from time to
time by the selling stockholders.  The term "selling stockholders" includes
donees, pledgees, transferees or other successors-in-interest selling shares
received after the date of this prospectus from a selling stockholder as a gift,
pledge, partnership distribution or other non-sale related transfer.  The
selling stockholders will act independently of us in making decisions with
respect to the timing, manner and size of each sale.  Such sales may be made in
the over-the-counter market or otherwise, at prices and under terms then
prevailing or at prices related to the then current market price or in
negotiated transactions.  The selling stockholders may sell their shares by one
or more of, or a combination of, the following methods:

     .    purchases by a broker-dealer as principal and resale by such broker-
          dealer for its own account pursuant to this prospectus,

     .    ordinary brokerage transactions and transactions in which the broker
          solicits purchasers,

     .    block trades in which the broker-dealer so engaged will attempt to
          sell the shares as agent but may position and resell a portion of the
          block as principal to facilitate the transaction,

     .    an over-the-counter distribution in accordance with the rules of the
          Nasdaq National Market,

     .    in privately negotiated transactions, and

     .    in options transactions.

     In addition, any shares that qualify for sale pursuant to Rule 144 may be
sold under Rule 144 rather than pursuant to this prospectus.

     To the extent required, this prospectus may be amended and supplemented
from time to time to describe a specific plan of distribution.  In connection
with distributions of the shares or otherwise, the selling stockholders may
enter into hedging transactions with broker-dealers or other financial
institutions.  In connection with such transactions, broker-dealers or other
financial institutions may engage in short sales of the common stock in the
course of hedging the positions they assume with selling stockholders.  The
selling stockholders may also sell the common stock short and redeliver the
shares to close out such short positions.  The selling stockholders may also
enter into option or other transactions with broker-dealers or other financial
institutions which require the delivery to such broker-dealer or other financial
institution of shares offered by this prospectus, which shares such broker-
dealer or other financial institution may resell pursuant to this prospectus (as
supplemented or amended to reflect such transaction).  The selling stockholders
may also pledge shares to a broker-dealer or other financial institution, and,
upon a default, such broker-dealer or other financial institution, may effect
sales of the pledged shares pursuant to this prospectus (as supplemented or
amended to reflect such transaction).

     In effecting sales, broker-dealers or agents engaged by the selling
stockholders may arrange for other broker-dealers to participate.  Broker-
dealers or agents may receive commissions, discounts or concessions from the
selling stockholders in amounts to be negotiated immediately prior to the sale.

     In offering the shares covered hereby, the selling stockholders and any
broker-dealers who execute sales for the selling stockholders may be deemed to
be "underwriters" within the meaning of the Securities Act in connection with
such sales.  Any profits realized by the selling stockholders and the
compensation of such broker-dealer may be deemed to be underwriting discounts
and commissions.

     In order to comply with the securities laws of certain states, if
applicable, the shares must be sold in such jurisdictions only through
registered or licensed brokers or dealers.  In addition, in certain states the
shares may not

                                      -19-
<PAGE>

be sold unless they have been registered or qualified for sale in the applicable
state or an exemption from the registration or qualification requirement is
available and is complied with.

     We have advised the selling stockholders that the anti-manipulation rules
of Regulation M under the Exchange Act may apply to sales of shares in the
market and to the activities of the selling stockholders and their affiliates.
In addition, we will make copies of this prospectus available to the selling
stockholders for the purpose of satisfying the prospectus delivery requirements
of the Securities Act.  The selling stockholders may indemnify any broker-dealer
that participates in transactions involving the sale of the shares against
certain liabilities, including liabilities arising under the Securities Act.

     At the time a particular offer of shares is made, if required, a prospectus
supplement will be distributed that will set forth the number of shares being
offered and the terms of the offering, including the name of any underwriter,
dealer or agent, the purchase price paid by any underwriter, any discount,
commission and other item constituting compensation, any discount, commission or
concession allowed or reallowed or paid to any dealer and the proposed selling
price to the public.

     We have agreed to indemnify the selling stockholders against certain
liabilities, including certain liabilities under the Securities Act.

     We have agreed with the selling stockholders to keep the Registration
Statement of which this prospectus constitutes a part effective until the
earlier of (i) such time as all of the shares covered by this prospectus have
been disposed of pursuant to and in accordance with the Registration Statement
or (ii) the second anniversary of the effective date of the Registration
Statement.


                                 LEGAL MATTERS

     The validity of the shares offered by this prospectus has been passed upon
by Hale and Dorr LLP.


                                    EXPERTS

     The consolidated balance sheets of SatCon as of September 30, 1998 and 1997
and the consolidated statements of income, stockholders' equity and cash flows
for each of the years in the three-year period ended September 30, 1998, have
been incorporated by reference herein and in the Registration Statement in
reliance upon the report of PricewaterhouseCoopers LLP, independent auditors,
incorporated by reference herein, and upon the authority of said firm as experts
in accounting and auditing.

                                      -20-
<PAGE>

                                    PART II

                    INFORMATION NOT REQUIRED IN PROSPECTUS


Item 14.  Other Expenses of Issuance and Distribution.

     The following table sets forth the various expenses to be incurred in
connection with the sale and distribution of the securities being registered
hereby, all of which will be borne by SatCon (except any underwriting discounts
and commissions and expenses incurred by the selling stockholders for brokerage,
accounting, tax or legal services or any other expenses incurred by the selling
stockholders in disposing of the shares).  All amounts shown are estimates
except the Securities and Exchange Commission registration fee.

          Filing Fee - Securities and Exchange Commission.........   $    5,893

          Legal fees and expenses.................................   $   60,000

          Accounting fees and expenses............................   $   30,000

          Miscellaneous expenses..................................   $   14,107
                                                                     ----------
               Total Expenses.....................................   $  110,000
                                                                     ==========

Item 15.  Indemnification of Directors and Officers.

     Section 102 of the Delaware General Corporation Law allows a corporation to
eliminate the personal liability of directors of a corporation to the
corporation or its stockholders for monetary damages for a breach of fiduciary
duty as a director, except where the director breached his duty of loyalty,
failed to act in good faith, engaged in intentional misconduct or knowingly
violated a law, authorized the payment of a dividend or approved a stock
repurchase in violation of Delaware corporate law or obtained an improper
personal benefit.  SatCon has included such a provision in its Certificate of
Incorporation.  This provision reads as follows:

          "To the maximum extent permitted by Section 102(b)(7) of the General
     Corporation Law of Delaware, a director of this Corporation shall not be
     personally liable to the Corporation or its stockholders for monetary
     demands for breach of fiduciary duty as a director, except for liability
     (i) for any breach of the director's duty of loyalty to the Corporation or
     its stockholders, (ii) for acts of omissions not in good faith or which
     involve intentional misconduct or a knowing violation of law, (iii) under
     Section 174 of the Delaware General Corporation Law, or (iv) for any
     transaction from which the director derived an improper personal benefit."

     Section 145 of the General Corporation Law of Delaware provides that a
corporation has the power to indemnify a director, officer, employee or agent of
the corporation and certain other persons serving at the request of the
corporation in related capacities against amounts paid and expenses incurred in
connection with an action or proceeding to which he is or is threatened to be
made a party by reason of such position, if such person shall have acted in good
faith and in a manner he reasonably believed to be in or not opposed to the best
interests of the corporation, and, in any criminal proceeding, if such person
had no reasonable cause to believe his conduct was unlawful; provided that, in
the case of actions brought by or in the right of the corporation, no
indemnification shall be made with respect to any matter as to which such person
shall have been adjudged to be liable to the corporation unless and only to the
extent that the adjudicating court like determines that such indemnification is
proper under the circumstances.  SatCon's Bylaws include the following
provision:

                                      II-1
<PAGE>

          "Reference is made to Section 145 and any other relevant provisions of
     the General Corporation Law of the State of Delaware.  Particular reference
     is made to the class of persons, hereinafter called "Indemnitees", who may
     be indemnified by a Delaware corporation pursuant to the provisions of such
     Section 145, namely, any person or the heirs, executors, or administrators
     of such person, who was or is a party or is threatened to be made a party
     to any threatened, pending or completed action, suit, or proceeding,
     whether civil, criminal, administrative, or investigative, by reason of the
     fact that such person is or was a director, officer, employee, or agent of
     such corporation or is or was serving at the request of such corporation as
     a director, officer, employee, or agent of another corporation, partnership
     joint venture, trust, or other enterprise.  The Corporation shall, and is
     hereby obligated to, indemnify the Indemnitees, and each of them in each
     and every situation where the Corporation is obligated to make such
     indemnification pursuant to the aforesaid statutory provisions.  The
     Corporation shall indemnify the Indemnitees, and each of them, in each and
     every situation where, under the aforesaid statutory provisions, the
     Corporation is not obligated, but is nevertheless permitted or empowered,
     to make such indemnification, it being understood that, before making such
     indemnification with respect to any situation covered under this sentence,
     (i) the Corporation shall promptly make or cause to be made, by any of the
     methods referred to in Subsection (d) of such Section 145, a determination
     as to whether each Indemnitee acted in good faith and in a manner he
     reasonably believed to be in, or not opposed to, the best interests of the
     Corporation, and, in the case of any criminal action or proceeding, had no
     reasonable cause to believe his conduct was unlawful, and (ii) that no such
     indemnification shall be made unless it is determined that such Indemnitee
     acted in good faith and in a manner he reasonably believed to be in, or not
     opposed to, the best interests of the Corporation, and, in the case of any
     criminal action or proceeding, had no reasonable cause to believe that his
     conduct was unlawful."

     SatCon has purchased directors' and officers' liability insurance which
would indemnify its directors and officers against damages arising out of
certain kinds of claims which might be made against them based on their
negligent acts or omissions while acting in their capacity as such.

                                      II-2
<PAGE>

Item 16.  Exhibits

  EXHIBIT NUMBER                      DESCRIPTION

    4.1(1)          Certificate of Incorporation of the Registrant.

    4.2(1)          Bylaws of the Registrant.

    4.3(2)          Certificate of Amendment of Certificate of Incorporation of
                    the Registrant, as filed with the Secretary of State of the
                    State of Delaware on May 12, 1997.

    4.4(2)          Bylaws Amendment of the Registrant.

    4.5(3)          Certificate of Amendment of Certificate of Incorporation of
                    the Registrant, as filed with the Secretary of State of the
                    State of Delaware on March 17, 1999.

    4.6(3)          Certificate of Designation of Series and Statement of
                    Variations of Relative Rights, Preferences and Limitations
                    of Preferred Stock, dated as of August 25, 1999, relating to
                    the Series A Convertible Redeemable Preferred Stock.

    5.1             Opinion of Hale and Dorr LLP.

    10.1(3)         Securities Purchase Agreement, dated as of August 25, 1999,
                    among the Registrant and the purchasers listed on Schedule I
                    thereto.

    10.2(3)         Registration Rights Agreement, dated as of August 25, 1999,
                    among the Registrant and the investors named on the
                    signature pages thereof.

    10.3(3)         Form of Warrants issued on August 25, 1999 in connection
                    with the sale of the Series A Convertible Redeemable
                    Preferred Stock.

    10.4(4)         Form of Common Stock Purchase Warrant issued to certain
                    individuals and entities on June 15, 1998.

    10.5(4)         Form of Common Stock Purchase Warrant issued to certain
                    individuals and entities on November 11, 1998.

    23.1            Consent of PricewaterhouseCoopers LLP.

    23.2            Consent of Hale and Dorr LLP, included in Exhibit 5.1 filed
                    herewith.

    24.1            Power of Attorney (See page II-6 of this Registration
                    Statement).

___________________

(1) Incorporated by reference to Exhibits to the Registrant's Registration
    Statement on Form S-1 (File No. 33-49286).

(2) Incorporated by reference to Exhibits to the Registrant's Quarterly Report
    on Form 10-Q for the period ended March 31, 1997.

(3) Incorporated by reference to Exhibits to the Registrant's Current Report on
    Form 8-K dated August 25, 1999.

(4) Incorporated by reference to Exhibits to the Registrant's Annual Report on
    Form 10-K for the fiscal year ended September 30, 1998.


                                      II-3
<PAGE>

Item 17.  Undertakings.

     The undersigned Registrant hereby undertakes:

     (1)  To file, during any period in which offers or sales are being made, a
post-effective amendment to this Registration Statement:

          (i)    To include any prospectus required by Section 10(a)(3) of the
     Securities Act of 1933, as amended (the "Securities Act");

          (ii)   To reflect in the prospectus any facts or events arising after
     the effective date of this Registration Statement (or the most recent post-
     effective amendment thereof) which, individually or in the aggregate,
     represent a fundamental change in the information set forth in this
     Registration Statement.  Notwithstanding the foregoing, any increase or
     decrease in the volume of securities offered (if the total dollar value of
     securities offered would not exceed that which was registered) and any
     deviation from the low or high end of the estimated maximum offering range
     may be reflected in the form of prospectus filed with the Commission
     pursuant to Rule 424(b) if, in the aggregate, the changes in volume and
     price represent no more than 20 percent change in the maximum aggregate
     offering price set forth in the "Calculation of Registration Fee" table in
     the effective Registration Statement; and

          (iii)  To include any material information with respect to the plan of
     distribution not previously disclosed in this Registration Statement or any
     material change to such information in this Registration Statement;

provided, however, that paragraphs (1)(i) and (1)(ii) do not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed with or furnished to the
Commission by the Registrant pursuant to Section 13 or Section 15(d) of the
Securities Exchange Act of 1934, as amended (the "Exchange Act"), that are
incorporated by reference in this Registration Statement.

     (2)  That, for the purposes of determining any liability under the
Securities Act, each post-effective amendment that contains a form of prospectus
shall be deemed to be a new registration statement relating to the securities
offered therein, and the offering of such securities at the time shall be deemed
to be the initial bona fide offering thereof.

     (3)  To remove from registration by means of a post-effective amendment any
of the securities being registered which remain unsold at the termination of the
offering.

     The Registrant hereby undertakes that, for purposes of determining any
liability under the Securities Act, each filing of the Registrant's annual
report pursuant to Section 13(a) or 15(d) of the Exchange Act (and, where
applicable, each filing of an employee benefit plan's annual report pursuant to
Section 15(d) of the Exchange Act) that is incorporated by reference in this
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein and the offering of such securities
at the time shall be deemed to be the initial bona fide offering thereof.

     Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors, officers and controlling persons of the
Registrant pursuant to the indemnification provisions described herein, or
otherwise, the Registrant has been advised that in the opinion of the Securities
and Exchange Commission such indemnification is against public policy as
expressed in the Securities Act and is, therefore, unenforceable.  In the event
that a claim for indemnification against such liabilities (other than the
payment by the Registrant of expenses incurred or paid by a director, officer or
controlling person of the Registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the securities being registered, the Registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the
Securities Act and will be governed by the final adjudication of such issue.

                                      II-4
<PAGE>

                                  SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, as amended, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-3 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Cambridge, Commonwealth of Massachusetts, on
September 15, 1999.

                              SATCON TECHNOLOGY CORPORATION



                              By:   /s/ David B. Eisenhaure
                                    ----------------------------------------
                                    David B. Eisenhaure
                                    President, Chief Executive Officer and
                                    Chairman of the Board

                                      II-5
<PAGE>

                       SIGNATURES AND POWER OF ATTORNEY


     We, the undersigned officers and directors of SatCon Technology
Corporation, hereby severally constitute and appoint David B. Eisenhaure,
Michael C. Turmelle, and Jeffrey N. Carp, Esq., and each of them singly, our
true and lawful attorneys with full power to any of them, and to each of them
singly, to sign for us and in our names in the capacities indicated below the
Registration Statement on Form S-3 filed herewith and any and all pre-effective
and post-effective amendments to said Registration Statement and generally to do
all such things in our name and behalf in our capacities as officers and
directors to enable SatCon Technology Corporation, to comply with the provisions
of the Securities Act of 1933, as amended, and all requirements of the
Securities and Exchange Commission, hereby ratifying and confirming our
signatures as they may be signed by our said attorneys, or any of them, to said
Registration Statement and any and all amendments thereto.

     Pursuant to the requirements of the Securities Act of 1933, as amended,
this Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.

       Signature                      Title                        Date
       ---------                      -----                        ----

/s/ David B. Eisenhaure      Chairman of the Board,           September 15, 1999
---------------------------  President, Chief Executive
   David B. Eisenhaure       Officer and Director
                             Principal Executive Officer)


/s/ Michael C. Turmelle      Director, Treasurer and Vice     September 15, 1999
---------------------------  President of Finance (Principal
   Michael C. Turmelle       Financial Officer and Principal
                             Accounting Officer)


/s/ James L. Kirtley, Jr.    Director and Vice President and  September 15, 1999
---------------------------  General Manager of the
   James L. Kirtley, Jr.     Technology Center


/s/ John P. O'Sullivan       Director                         September 15, 1999
---------------------------
   John P. O'Sullivan


/s/ Marshall J. Armstrong    Director                         September 15, 1999
---------------------------
   Marshall J. Armstrong


/s/ Anthony J. Villiotti     Director                         September 15, 1999
---------------------------
   Anthony J. Villiotti


                                      II-6

<PAGE>

                                EXHIBIT INDEX


 EXHIBIT NUMBER                        DESCRIPTION

    4.1(1)          Certificate of Incorporation of the Registrant.

    4.2(1)          Bylaws of the Registrant.

    4.3(2)          Certificate of Amendment of Certificate of Incorporation of
                    the Registrant, as filed with the Secretary of State of the
                    State of Delaware on May 12, 1997.

    4.4(2)          Bylaws Amendment of the Registrant.

    4.5(3)          Certificate of Amendment of Certificate of Incorporation of
                    the Registrant, as filed with the Secretary of State of the
                    State of Delaware on March 17, 1999.

    4.6(3)          Certificate of Designation of Series and Statement of
                    Variations of Relative Rights, Preferences and Limitations
                    of Preferred Stock, dated as of August 25, 1999, relating to
                    the Series A Convertible Redeemable Preferred Stock.

    5.1             Opinion of Hale and Dorr LLP.

    10.1(3)         Securities Purchase Agreement, dated as of August 25, 1999,
                    among the Registrant and the purchasers listed on Schedule I
                    thereto.

    10.2(3)         Registration Rights Agreement, dated as of August 25, 1999,
                    among the Registrant and the investors named on the
                    signature pages thereof.

    10.3(3)         Form of Warrants issued on August 25, 1999 in connection
                    with the sale of the Series A Convertible Redeemable
                    Preferred Stock.

    10.4(4)         Form of Common Stock Purchase Warrant issued to certain
                    individuals and entities on June 15, 1998.

    10.5(4)         Form of Common Stock Purchase Warrant issued to certain
                    individuals and entities on November 11, 1998.

    23.1            Consent of PricewaterhouseCoopers LLP.

    23.2            Consent of Hale and Dorr LLP, included in Exhibit 5.1 filed
                    herewith.

    24.1            Power of Attorney (See page II-6 of this Registration
                    Statement).

___________________

(1) Incorporated by reference to Exhibits to the Registrant's Registration
    Statement on Form S-1 (File No. 33-49286).

(2) Incorporated by reference to Exhibits to the Registrant's Quarterly Report
    on Form 10-Q for the period ended March 31, 1997.

(3) Incorporated by reference to Exhibits to the Registrant's Current Report on
    Form 8-K dated August 25, 1999.

(4) Incorporated by reference to Exhibits to the Registrant's Annual Report on
    Form 10-K for the fiscal year ended September 30, 1998.