The North American Electric Reliability Corporation’s (NERC) 2025 State of Reliability report, which reviews bulk-power system performance in 2024, finds early evidence that battery energy storage systems (BESSs) are strengthening primary frequency response in regions with high storage penetration.
NERC documented several events in which BESSs supplied 100% of frequency-regulation capacity, and they routinely covered more than 70% of needs during system disturbances.
The graph from the report highlights the chief advantage of BESSs, which is speed. During a frequency dip, the dotted line — representing BESS response — reacts faster than conventional generation. This leads to the frequency nadir— the low point of frequency — being shallower and shorter.
Fast action is critical. If frequency drifts for too long, generating units disconnect to protect themselves, as happened recently in Spain. BESSs have long proved their worth in the fast acting frequency space: Australia’s Hornsdale system — the first big BESS on the power grid in the world — kept the grid stable after a large coal plant tripped offline.
Older solar plants with legacy inverter settings can struggle when frequency strays outside normal limits, a stability concern the report also flags.
From 2021 to 2024, Texas retired some gas and coal units yet increased available frequency support, mainly through new BESSs. In Texas, BESSs are required by rule to provide frequency support, NERC notes.
In early May, the California Energy Commission released a report also suggesting that the state’s power grid had become more stable in recent years as BESS deployments increased.
The report noted that in 2024, the CAISO region hit 100% “clean energy” every “three out of five days”, and that despite periods of extreme heat, the grid didn’t issue a single Flex Alert for the whole year.
With the power grid shifting toward inverter based resources, versus thermal power plants, BESS systems are now being called on to become the base of stability for the grid. Grid forming inverters have been deploying in leading solar market Australia since 2021. New research is suggesting that BESS units with grid forming capabilities can enable more solar to run on local power grids.
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