Battery runtime calculator
Estimate constant-load runtime from stored energy, a usable fraction and discharge efficiency, while checking the AC power limit.
Educational reference only. Examples and calculator results are not approved installation designs, equipment selections or operating instructions.
Your inputs
Results update as you edit. Use a decimal point. Default values are hypothetical, not recommended equipment sizes.
Energy at the storage-side boundary, before the two factors below.
Available share after the chosen reserve or state-of-charge window.
One-way delivery efficiency, not round-trip efficiency.
Include any auxiliary loads in this total.
The load must not exceed the battery/inverter’s AC power limit.
Illustrative result
- Estimated constant-load runtime
- 3.24 h
- Estimated AC-delivered energy
- 810 kWh
Worked steps
- Edelivered = 1,000 × 0.9 × 0.9 = 810 kWh
- t = 810 / 250 = 3.24 h
- Power check: 250 kW ≤ 500 kW AC limit
Calculations use unrounded values; displayed steps are rounded to three decimal places or five significant digits for extreme values.
Formula and units
Edelivered (kWh) = Estored × usable fraction × discharge efficiency; t (h) = Edelivered / PAC
Change one input to see its effect. Inputs are calculated in your browser and are not submitted to a calculation service.