The Energy Storage Report 2024

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Regulator quashes ERCOT’s proposed state-of-charge rules for BESS


The Public Utility Commission of Texas has ordered the state’s grid operator ERCOT to rescind state-of-charge (SOC) rules requiring batteries to hold additional capacity to provide ancillary services.

The Commission ordered ERCOT to remove its proposed NPRR (Nodal Protocol Revision Request) 1186 in a letter last week (18 January) signed by the Commission’s interim chair and two of its four commissioners.

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By codifying a temporary rule, NPRR 1186 would have meant battery energy storage system (BESS) resources on the ERCOT grid would need to hold – operators argued – more capacity than required when providing ancillary services (such as ERCOT Contingency Reserve Service, Reg-Up and Reg-Down, Responsive Reserve Service or spinning reserve).

The rules also meant BESS technology was having its energy supplies monitored and mandated in real-time in a way no other resources are. Operators said it was an unnecessary limitation on their ability to operate considering penalties already exist for failing to provide contracted ancillary services, for all types of resources including batteries.

Although the Commission’s commentary on NPRR 1186 and its reasons for rejecting it are not on its filings register, commissioner James Glotfelty was quoted in local press saying:

“This presentation that ERCOT put together shows me one thing, really, and that is that every resource fails. So, singling out ancillary services providers of battery storage is discriminatory. Gas plants fail. Nuclear plants fail. Coal plants fail.” 

Companies that submitted filings opposing NPRR 1186 in the lead-up to the Commission’s decision last week were BESS operators Engie, Aypa Power, Eolian and Plus Power (co-filed) and Jupiter Power, as well as environmental organisation Sierra Club. Others that commented earlier in the stakeholder process opposing include operators Spearmint Energy and Key Capture Energy and energy trader Aspire Power.

The only filing in support of NPRR 1186 was oil and gas major Shell, which operates thermal power plants in the state (alongside some BESS). Thermal power plants were historically the main provider of ancillary services, but have increasingly been displaced by BESS which are faster-reacting, cheaper and (obviously) less polluting. ERCOT expects the capacity of BESS on its grid to grow to 9.5GW by October 2024.

Read all the filings related to NPRR 1186, including the companies’ letters opposing or supporting it, and the Commission’s final decision, on its website here.’ publisher Solar Media will host the 5th Energy Storage Summit USA, 19-20 March 2024 in Austin, Texas. Featuring a packed programme of panels, presentations and fireside chats from industry leaders focusing on accelerating the market for energy storage across the country. For more information, go to the website.

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