ESS (energy storage system)
energy storage · battery storage · BESS
An ESS stores electricity and releases it when needed. Korean law calls it an 'electricity storage device'.
An ESS (energy storage system) holds electricity in a medium such as a battery and later feeds it back to the grid. The Electric Utility Act calls it an 'electricity storage device'.
Storing surplus power when renewables run high can cut curtailment. In May 2025 the Korea Power Exchange announced a competitive tender for its central contract market for ESS: 500 MW / 3,000 MWh on the mainland and 40 MW / 240 MWh on Jeju.
How to read it: MW is how much power it can release at once; MWh is how much it can hold. 500 MW / 3,000 MWh can run at full output for six hours.