🔋 Outage Runtime Calculator
Estimate how long a battery power station will run your appliances during an outage.Free, no signup, no ads on this page. Built and maintained byHilario Herrera in Florida.
This page is free to link to or reference in hurricane preparedness guides — no permission needed. It carries no advertising and no affiliate links. If you need the underlying appliance-wattage data, the open dataset is CC BY 4.0. Questions or embed requests: [email protected].
2. What you'd run at the same time:
— hours
How this calculation works
Runtime equals usable capacity divided by the total watts you are running. AC loads are derated 15% for inverter conversion loss; loads that run off USB or 12V ports bypass the inverter and are derated 5%. Appliance figures are typical running draws, not nameplate maximums — the microwave figure is real input draw, because a "1,000 W" oven's rating describes cooking output, not consumption.
Before reporting hours, the calculator checks two hard limits: whether the station's continuous output can carry the load at all, and whether its peak rating covers the startup surge of motor appliances (roughly 3–6× running watts for a compressor). If either fails, no runtime is shown, because the honest answer is that the unit cannot run that load.
Compressor appliances cycle on and off, so real-world refrigerator-only runtime is often 2–3× longer than continuous-draw math suggests. Full assumptions are on themethodology page. These are estimates from published specifications, not measurements of your specific appliance — the label on your unit beats our math.
Related free resources
Pre-storm systems check (interactive readiness checklist) ·100 backup power questions answered ·Generator safety rules (CPSC/CDC sourced) ·Open equipment dataset (CC BY 4.0)
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