Changes to rules governing payments for fast-response assets in the Pennsylvania– New Jersey–Maryland (PJM) electricity market earlier this decade allowed batteries to compete in providing frequency regulation services. This was followed, in 2013, by a mandate from the California
Public Utilities Commission (CPUC) requiring that the utilities it regulates build 1.3GW of energy storage capacity by 2020. Similarly, the National Grid in the UK has conducted enhanced frequency response auctions in which batteries provided the bulk of the capacity.
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