C-rate

C-rate is a measure of how fast a battery charges or discharges relative to its rated energy capacity, expressed as a multiple of that capacity per hour: a 1C rate fully discharges a battery in one hour, 0.5C takes two hours, and 2C takes thirty minutes. It is calculated by dividing a system's power rating in kW by its energy capacity in kWh, so a 100 kWh battery paired with a 50 kW inverter runs at 0.5C and yields two hours of duration at full power. BESS spec sheets often list power and capacity separately rather than stating C-rate directly, so buyers have to compute it to compare products. Most grid-scale storage built for daily solar shifting sits in the 0.25C-0.5C range (four- to two-hour duration), while shorter-duration systems built for frequency regulation run at 2C or higher; a higher C-rate also degrades a lithium-ion cell faster, so it doubles as a proxy for expected cycle life.