Battery runtime planner

Enter your own power station and loads. Estimate running time, then check whether each outage window fits.

Power station

Battery capacity Wh

Usable capacity % of label

AC conversion loss %

AC output limit W continuous

AC surge limit W

Replace these illustrative entries with the rated output and usable energy of your own unit. Conversion loss is a user assumption, not a guaranteed efficiency.

Running load

Total running devices W

Combined starting peak W

Enter the total running watts of devices used together. Starting peak is the maximum combined draw during a start, including devices already running. It is not an extra load for the whole outage.

Outage windows

Short outage hours

Long outage hours

Extended outage hours

Estimate

No recharging, solar input, changing load, idle draw, temperature derating, aging, or battery cutoff behavior is modeled. Nameplate Wh is not a promise of AC output. Match plugs, voltage, waveform and manufacturer's surge-duration specification before relying on backup power. Do not use this estimate for medical or other safety-critical equipment.

Method: usable AC energy = capacity Wh × usable fraction × (1 - loss fraction); runtime = usable AC Wh ÷ running W. Required nameplate capacity = running W × hours ÷ (usable fraction × conversion fraction). Starting peak is checked separately against the unit's surge rating. Sources: U.S. Department of Energy, Battery Power for Your Residential Solar Electric System (2002), derives energy from wattage × hours and discusses usable battery capacity; U.S. Department of Energy, Analysis of Refrigeration Units in Off Grid PV/Wind Hybrid Systems on Tribal Land (2018), describes DC-to-AC inverter conversion and the short starting-power surge of a refrigerator motor. Accessed September 27, 2026. Assumptions and equation here are planning estimates, not product ratings.