Most energy generated by utilities flows into the grid to meet the daily power needs of homes and businesses. Some energy, however, is stored in batteries to use later during times of high demand. When the extra power is needed, the battery discharges its energy to the grid to meet the demand. The battery then recharges at night when demand is low.
Homes and businesses can use batteries of their own to save money through a practice known as peak shaving. When energy demand on the grid is high, prices rise. When that happens, stored energy in batteries is released to supply power to the home or business, reducing electricity bills. The batteries then recharge at night, when demand and prices are low, and can also store energy generated by small-scale wind or solar installations.