Storage duration
How long a storage system can deliver its rated power.
A battery beside a clock represents the energy-to-power ratio, not a particular operating schedule.
Storage duration is how long a fully charged system can deliver a stated discharge power. Nominal duration is usable energy capacity divided by that power, with both ratings measured on the same AC or DC basis.
Dividing energy capacity by power
Divide usable energy in MWh by discharge power in MW and the units reduce to hours. Both values must use the same measurement boundary. Do not divide a battery’s stored DC energy by an AC power rating without accounting for the conversion and operating limits.
Lower discharge power can extend delivery time. Actual duration also depends on starting state of charge, temperature, degradation, and any energy reserved for other services. Losses should be included where the quoted usable-energy rating has not already allowed for them.
Why it matters
Duration helps distinguish short bursts of support from moving larger amounts of energy across several hours.