A new report fromSEPA estimates a total of 760.3MWh of energy storage was interconnected US-wide in 2018, hitting a cumulative market size of 1,966.6MWh.

According to the organisation, investor-owned utilities (IOUs) dominated last year, accounting for 64.3 percent (488.6MWh) of nation-wide energy storage installations.

However, public power utilities and electric cooperatives were in catch-up mode after seeing a dramatic ramp-up in 2018, SEPA found.

They interconnected 271.7MWh of storage last year – a whopping 300% jump from 2017. Public power was the fastest-growing segment, increasing by more than 1,400%.

Utilities Southern California Edison, Kaui Island Cooperative and Pacific Gas & Electric boasted the most MWh storage capacity in the country at 153MWh, 102MWh, and 73.2MWh respectively.

Across market segments, utility-supply storage witnessed the largest roll-out, with 2018's installations of 394.8MWh 11.3% above the 2017 figures.

Non-residential storage grew by 34.9%, with deployments totaling 189.9MWh. California interconnected more non-residential storage than any other state, at 151.9MWh, trouncing runners-up Colorado (18MWh connected) and New York (12.3MWh).

Residential storage deployments quintupled in 2018 from the previous year and totaled 189.9MWh. Residents in California, Hawaii, and Vermont led the charge, interconnecting 99.9MWh, 33.6MWh and 13.5MWh respectively.

According to Mac Keller, co-lead author and research associate at SEPA, the US storage market is “primed for continued growth” from its current size of 1,966.6MWh.

- Energy storage deployments are accelerating, driven by increasingly compelling economics and favorable state policies and residential programs in California, Hawaii, and Vermont. Beyond traditional back-up generation, storage is able to provide ancillary services, ramping, smoothing, peaking and baseload generation services to meet the demands of an increasingly diversified and distributed electrical system, he said.

The report notes that the cost of building lithium-ion storage assets has declined by 72.9% since 2013.