The combined power rating of installed electricity storage in the US grew 181.5 MW over the past year, and totaled 565.5 MW at the end of the second quarter of 2017, according to data filed with the US Federal Energy Regulatory Commission.
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The data show 22 companies own and operate 45 grid-connected energy storage facilities in 12 states. All of the installations are battery storage systems bar two flywheel units. Of the installed power rating, 276.8 MW is used for frequency regulation.
A regional breakdown of the data shows 22 battery systems and one flywheel system are located in PJM Interconnection's footprint and have a combined power rating of 301 MW. The energy rating, or the duration in terms of hours of storage a system provides as measured in megawatt-hours, was not made available by companies for all of the systems in PJM.
However, there were 10 battery storage systems operational in the California Independent System Operator footprint at the end of Q2 that had a combined power rating of 114.2 MW and a reported combined energy rating of 405 MWh. The largest, San Diego Gas & Electric's 30-MW Escondido facility, installed at the end of the first quarter, has an energy rating of 120 MWh.
A lithium-ion battery system installed by AES Energy Storage at SDG&E's Escondido substation in February was part of the California Public Utilities Commission's efforts to address the loss of the Aliso Canyon natural gas storage facility north of Los Angeles that supplies gas to peaking units.
The Escondido system consisted of 400,000 batteries packed into 24 containers. Also in Q1, AES Energy Storage, again in partnership with SDG&E, brought a 7.5-MW, 30 MWh battery system at the utility's El Cajon substation into service.
The Q2 2017 Energy Storage Rankings to be published in Platts Megawatt Daily, takes into account the difference between who builds a facility and who owns it.
AES, which owns three systems in PJM and one in the Midcontinent Independent System Operator market that have a combined power rating of 83.3 MW, holds the top position in the ranking.
Second in the table is NextEra Energy Resources, which owns four PJM battery storage facilities and one in the ISO New England footprint with a combined power rating of 76.4 MW and an energy rating of 38.2 MWh. NextEra's largest facility -- coming in at 20 MW, 10 MWh -- is its Frontier Battery Energy Storage unit in New Jersey.
Invenergy Investment, which owns a small storage facility in ERCOT but also a 31.5-MW facility in West Virginia and a 36-MW, 13.8-MWh facility in Illinois, is ranked third.
Ranked fourth is Southern California Edison, which owns four battery storage units in California, including the 20-MW, 80-MWh Mira Loma facility that was installed in January by Tesla.
SoCal Ed's facilities have a combined power rating of 48 MW, and a combined energy rating of 120.4 MWh.
By owning the Escondido and El Cajon substation facilities, SDG&E is ranked 8th in terms of those units' combined power rating of 37.5 MW. However, the utility is top ranked in terms of energy rating. The combined energy rating of SDG&E's two facilities is 150 MWh.
--Jeffrey Ryser, firstname.lastname@example.org
--Edited by Keiron Greenhalgh, email@example.com