Active Power Doubles Energy of its Extended Runtime Product; Battery-Free Prototype Produces 80 kW for 15 Minutes; Remains on Milestone Track.

Energy Editors/Business Editors

AUSTIN, Texas--(BUSINESS WIRE)--June 9, 2004

Active Power, Inc. (Nasdaq:ACPW) today announced that it successfully completed the second of five milestones for its new battery-free energy storage system by operating a prototype at 80 kilowatts (kW) for 15 minutes. The new prototype delivers double the energy of the previous unit and has achieved the desired output power for the first version of the product.

Active Power's extended runtime product is initially slated to replace lead-acid batteries in the 3-phase Uninterruptible Power Supply (UPS) market below 100 kilovolt-amps (kVA), which is approximately 45% of the overall $2 billion 3-phase UPS market. Follow-on versions of this technology platform will be directed toward the low power telecommunications sector and its approximately $4 billion backup power market.

"This new product opens up several low power market segments that our current products don't address," stated Joe Pinkerton, Chairman and CEO of Active Power, Inc. "By delivering well over 20 times the energy of our current flywheel, the new battery-free product will allow us to satisfy the extended runtime demands of an entirely new set of customers."

As outlined earlier this year, the company has set forth the following additional milestones to be completed over the remainder of 2004:

-- Deliver 10 kW for 2 hours in Q3;

-- Unveil extended runtime technology publicly in Q3; and

-- Ship first alpha units to customers in Q4.

With over 500 units installed worldwide and more than 8 million hours of field operation, Active Power's products are a proven alternative to battery-based systems. The company offers the industry's broadest range of battery-free power quality solutions: the CleanSource DC product line, which is compatible with all leading UPS brands and is available in the 100 kW to 2000 kW range, and the CleanSource UPS product family, available from 65 kVA to 3600 kVA. Recognized by Frost & Sullivan for

its ability to satisfy customer needs with new and innovative products, Active Power continues to rapidly expand its product line to address the needs of new market segments and geographies. For more information visit www.activepower.com, e-mail [e-mail] or call 1-877-FLYWHEEL (359-9433).

About Active Power:

Active Power, Inc. (www.activepower.com) designs, manufactures and markets battery-free power quality products that provide the consistent, reliable electric power required by today's digital economy. An ISO 9001-registered company, Active Power is the first to commercialize a flywheel energy storage system, CleanSource(R) that provides a highly reliable, low-cost and non-toxic replacement for lead-acid batteries used in conventional power quality installations.

Cautionary Note Regarding Forward-Looking Statements:

This release may contain forward-looking statements that involve risks and uncertainties. Any forward-looking statements and all other statements that may be made in this news release that are not historical facts are subject to a number of risks and uncertainties, and actual results may differ materially. Specific risks include delays in new product development, product performance and quality issues and the acceptance of our current and new products by the power quality market. Please refer to Active Power filings with the Securities and Exchange Commission for more information on the risk factors that could cause actual results to differ.

Active Power and our Active Power logo and CleanSource are registered trademarks of Active Power, Inc. All other trademarks are the properties of their respective companies.