1. Choose what stays on
Start with an example or add your own appliances. Hours are total running hours per 24-hour day, not hours plugged in.
Saving is optional and local to this browser. Shared links include your appliance labels and settings. No account or email required.
Base configurations worth checking
How the estimate works
Daily appliance energy is the sum of running watts × hours used. For an outage, we scale by outage hours ÷ 24. Required battery Wh = (appliance Wh ÷ AC efficiency + inverter idle W × outage hours) ÷ (1 − reserve fraction).
Short outages use a proportional daily profile. If all of an appliance’s use falls inside that outage, increase its hours/day accordingly or calculate that short event separately. A 12-hour overnight outage will not necessarily use half a normal day’s energy.
Startup needs a separate check
Running output assumes every active appliance could run together. Starting demand adds the largest single appliance’s extra starting watts. Multiple simultaneous motor starts can exceed this estimate. Published surge ratings have time limits; verify the manufacturer’s manual, outlet limits and the actual load.
Replace examples with measured values
The fridge, office and overnight presets are illustrative inputs, not typical-use claims. Use a plug-in meter, appliance label or manual. CPAP power varies with heated humidifiers and tubing; confirm a suitable backup with the equipment manufacturer. A calculated match is not medical-backup certification.
No automatic expansion assumptions
Matching uses base capacity, running output and native voltage only. It does not silently combine batteries or count solar generation. For a longer outage, investigate verified expansion configurations and use the solar recharge calculator. Read the full sizing guide for wiring and equipment checks.
Sources and model limitations
Manufacturer sources and check dates are shown alongside matching products. The public dataset contains the specifications. Planning assumptions are not manufacturer guarantees or physical test results. Voltage, connector compatibility and transfer equipment need a separate check before connecting a home circuit.