Power calculator

RV Battery Runtime Calculator

Estimate how long a battery bank can support a steady electrical load. This is a planning estimate; real runtime changes with battery age, temperature, inverter behavior, surge loads and appliance cycling.

Battery-bank capacity (Ah)

Nominal voltage (V)

Usable capacity (%)Use a conservative figure appropriate for your battery chemistry and manufacturer guidance.

Inverter/system efficiency (%)

Average electrical load (watts)

Nominal energy—

Estimated usable energy—

Approx. runtime—

Formula: usable Wh ≈ amp-hours × voltage × usable-capacity % × system-efficiency %. Runtime ≈ usable Wh ÷ average load watts. AC appliance startup surges and cycling can materially change real results.

Average load matters more than nameplate peak

A refrigerator, furnace blower or air conditioner may cycle rather than draw continuously. For useful planning, estimate average energy use over the period you care about instead of assuming the peak wattage runs every minute.

Battery chemistry changes usable capacity

Different battery types and manufacturers specify different recommended depth-of-discharge and operating limits. Use the battery maker’s guidance rather than a generic percentage when planning a real system.