Power & Electrical
Battery Runtime Calculator
Estimate runtime from battery capacity, voltage, usable percentage, efficiency and load.
Battery performance varies with age, temperature, discharge rate and inverter/load efficiency.
Notes and next steps
How it works
Estimate runtime from battery Ah, voltage, load, usable capacity and efficiency.
Estimating method: Watt-hours = amp-hours × voltage. Runtime hours = watt-hours × usable percentage ÷ 100 × efficiency percentage ÷ 100 ÷ load watts.
Worked example
100 Ah at 12 V is 1200 Wh. At 80% usable and 90% efficiency with a 100 W load, runtime is 8.64 hours.
Common mistakes
- Using full capacity instead of usable capacity.
- Ignoring inverter efficiency.
- Forgetting battery age and temperature.