Beacon Power is an American limited liability company and wholly owned subsidiary of Rockland Capital LLC specializing in flywheel-based energy storage headquartered in Tyngsboro, Massachusetts. Beacon designs and develops products aimed at utility frequency regulation for power grid operations. The storage systems are designed to help utilities match supply with varying demand by storing excess power in arrays of 2,800-pound (1,300 kg) flywheels at off-peak times for use during peak demand. Beacon Power was founded in Woburn, Massachusetts in 1997 as a subsidiary of SatCon Technology Corporation, a maker of alternative energy management systems. The company went public in 2000.