Beacon Power Receives Certification for Smart Power M5 Inverter System from Underwriters Laboratories; Completed Production Units Ready for Immediate Shipment to Distributors.

Energy Editors/Business Editors/High-Tech Writers

WILMINGTON, Mass.--(BUSINESS WIRE)--Dec. 11, 2003

Beacon Power Corporation (NASDAQ: BCON), a leader in sustainable energy storage and power conversion systems, announced that the Smart Power M5 system has been approved for listing by Underwriters Laboratories (UL) in both the U.S. and Canada. Achieving UL approval is the final step in making a product fully available for commercial sale.

"Gaining UL approval for the Smart Power M5 is a significant accomplishment, and one we believe the industry has been waiting for," said Bill Capp, Beacon Power president and CEO. "The notice we received yesterday authorizes us to ship units with the UL label. The entire Beacon team deserves credit for successfully bringing this product through UL approval in a professional and timely manner."

The Smart Power M5 is designed for use in grid-connected solar power applications, and addresses the needs of customers who have concerns about the stability and reliability of the electrical grid. The Smart Power M5 immediately converts to an independent battery back-up mode when the grid fails, continuing to provide power to critical loads. It is also the most compact, easy to install and efficient product in this category.

About Underwriters Laboratories

Underwriters Laboratories Inc. (UL) is an independent, not-for-profit product safety certification organization that has been testing products for more than a century. UL has an undisputed reputation as the leader in U.S. product safety and certification.

About Beacon Power Corporation

Beacon Power Corporation (NASDAQ: BCON) designs and develops sustainable energy storage and power conversion solutions that provide reliable electric power for the renewable energy, telecommunications, distributed generation and UPS markets. Beacon's latest product is the Smart Power M5, a 5-kilowatt power conversion system for grid-connect solar power applications. The Smart Power M5 is a UL-approved, "all-in-one" power conversion system incorporating multiple high-performance components in one unit that delivers instantaneous power in the event of a grid outage. Beacon is also known for its advanced flywheel-based Smart Energy systems, designed to provide reliable, environmentally friendly power quality solutions for electric utility transmission and distribution and other applications.

For more information call 888-938-9112, or visit www.beaconpower.com.

Safe Harbor Statements under the Private Securities Litigation Reform Act of 1995:

Material contained in this press release may include statements that are not historical facts and are considered "forward-looking" within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements reflect Beacon Power Corporation's current views about future events and financial performances. These forward-looking statements are identified by the use of terms and phrases such as "believe," "expect," "plan," "anticipate," and similar expressions identifying forward-looking statements. Investors should not rely on forward-looking statements because they are subject to a variety of risks, uncertainties, and other factors that could cause actual results to differ materially from Beacon Power Corporation's expectation. These factors include: a short operating history; a history of losses and anticipated continued losses from operations; a need to raise additional capital combined with a questionable ability to do so; conditions in target markets; no experience manufacturing any product on a commercial basis; the company has only recently entered into the renewable energy market through its inverter products, and hence, has only limited experience in this sector; no commercial contracts for sales to date; the dependence of sales on the achievement of product development and commercialization milestones; the uncertainty of the political and economic climate of any foreign countries into which Beacon hopes to sell, including the uncertainty of enforcing contracts and the potential substantial fluctuation in currency exchange rates in those countries; significant technological challenges to successfully complete product development; dependence on third-party suppliers; intense competition from companies with greater financial resources; possible government regulation that would impede the ability to market products; possible product liability claims and the negative publicity which could result; any failure to protect intellectual property; the possible need in the future to hire and retain key executives, particularly in light of the substantial workforce reductions during 2001 and 2002; the recent volatility in the stock price of companies operating in the same sector; the power of controlling shareholders and the limited ability of others to influence the outcome of matters put to the vote of shareholders. These factors are elaborated upon and other factors may be disclosed from time to time in Beacon Power Corporation's filings with the Securities and Exchange Commission. Beacon Power Corporation expressly does not undertake any duty to update forward-looking statements.