According to a recent report by Platts, the combined power rating of installed electricity storage in the U.S. grew 181.5 megawatts (MW) over the past year to a new high of 585.5 MW at the end of the second quarter of 2017, based on reports filed with the U.S. Federal Energy Regulatory Commission. This means that almost one-third of the current installed electricity storage has come online in just the last 12 months.

According to the report, 22 companies own and operate 45 grid-connected storage facilities in 12 states, all of which are battery storage systems with the exception of two flywheel units.

Of the installed power rating, approximately half (276.8 MW) are used for frequency regulation. The remaining are in place to provide ancillary services, allow for the integration of additional renewables, and provide an alternative to costly grid infrastructure upgrades (e.g., installing storage units in lieu of having to upgrade distribution lines in areas of growing power demand).

One of the reasons for the rapid growth in utility-scale electricity storage is the fact that prices for storage units continues to decrease. Another is that the technology is improving such that storage is lasting longer and is more reliable.

Leaders in the installation of electricity storage include AES, NextEra Energy Resources, Invenergy Investment, Southern California Edison, and San Diego Gas & Electric.