The Energy Storage Report 2024

Now available to download, covering deployments, technology, policy and finance in the energy storage market

Stem, Prometheus complete first of three 2024 BESS projects for Arizona co-ops


System integrator Stem Inc and developer Prometheus Power have deployed the first of three BESS projects in Arizona for utilities in the AEPCO co-operative.

The 40MWh battery energy storage system (BESS) was added to an existing 20MW solar PV plant for Sulphur Springs Valley Electric Co-op (SSVEC), part of the non-profit member-owned Arizona Electric Power Cooperative (AEPCO).

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The Sulphur Springs project is one of three similarly sized deployments that Stem and Prometheus are deploying for AEPCO utilities in Arizona, all of which are expected to be online by the end of the year.

Stem is employing its Athena energy management system (EMS) software platform to operate and monitor the project. A photo provided in the announcement, shown above, indicates that the BESS units used for the project were the Stack750e that are part of system integrator Powin’s Centipede grid-scale BESS platform.

Stem Inc has been active in the co-operative utility segment which the company’s CEO John Carrington said is a significant part of the grid-scale energy storage market in the US.

“More than 900 electric co-ops across 48 states make up the largest electric utility network in the U.S. The segment is forecasted to be one of the fastest growing segments of the front-of-the-meter (FTM) market through the end of this decade and is projected to represent over 20% of all future storage deployments,” Carrington said.

Stem Inc said in May that it expected positive EBITDA in 2024 despite a dip in revenues and bookings in the first quarter of the year, something seen by other US-focused system integrators.

Arizona meanwhile continues to grow as a major energy storage market in the US, among the most active behind leaders California and Texas. In the last few months, Leeward signed a cross-border PPA for a 450MWh BESS, Plus Power secured US$82 million tax equity for a BESS project while the largest in the state was brought online by SRP and NextEra.

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