June 25 (Reuters) - Electric utilities in the U.S. are increasingly turning to batteries to shift power from periods of low prices to high-priced ones, according to an analysis from the U.S. Energy Information Administration.

The strategy, referred to as arbitrage, involves utilities charging batteries by buying electricity during low-cost periods and then selling that electricity when electricity prices increase. Arbitrage is now the primary use case for 10,487 MW of battery capacity in the U.S., the EIA said.

Energy storage technologies like batteries allow electric utilities to store power for later use, manage supply and demand in real time, and help prevent blackouts, among other use cases.

Utilities are also using batteries to bolster electric-grid reliability, the analysis found. Other instances of battery use include dealing with excess wind and solar power on the grid.

Electric utilities in the U.S. were operating 575 batteries, reflecting a total capacity of 15,814 MW, at the end of 2023 -- a figure that the EIA expects will more than triple by the end of 2028, with another 35,953 MW of battery storage added to the grid.

In California, for instance, battery storage on the grid has ramped up dramatically after the state experienced rolling blackouts during a heat wave in 2020. In 2022, batteries accounted for 2.4% of generation during the evening hours of another heat wave, the California Independent System Operator reported.

Earlier this month, Entergy and a unit of NextEra Energy signed an agreement to develop up to 4.5 gigawatts (GW )of new solar and energy storage projects, expected to provide renewable energy to more than 3 million customers in Arkansas, Louisiana, Mississippi and Texas. (Reporting by Kavya Balaraman in Bengaluru Editing by Matthew Lewis)