C-rate
Also known as: Charge Rate, Discharge Rate
A measure of how fast a battery is charged or discharged relative to its capacity. A 1C rate means the battery is fully charged or discharged in one hour; 0.5C means two hours; 2C means 30 minutes. Utility-scale BESS typically operates at 0.5C (2-hour duration) or 0.25C (4-hour duration).
In energy storage
C-rate directly determines the power-to-energy ratio and therefore the duration of a BESS. A 100 MW / 200 MWh system operates at 0.5C; the same battery capacity paired with 50 MW of PCS would be 0.25C (4-hour duration).