The U.S. electric grid operates at a frequency near 60 Hz, with generation and loads adjusted to keep the frequency within a few tenths of 60 Hz. Larger deviations from this base frequency are an indicator of grid distress, i.e. over-generation or overload. Frequency regulation of the electric grid can be provided by batteries, which can respond in milliseconds, to help continuously maintain grid frequency in an optimal operation range by exchanging power with the grid.
To solve this problem, East Penn Manufacturing Co., a battery manufacturer located in Lyon Station, PA is demonstrating battery energy storage that can be interconnected to the electric grid and provide services such as frequency regulation and peak shaving. These services support grid stability and increased renewable generation on the grid. In 2010, East Penn entered a cooperative agreement totaling $5,087,269, including $2,543,523 of funding from the U.S. Department of Energy's Smart Grid Demonstration Program (SGDP) to build an energy storage facility to support electric grid operation.