Power Station Runtime Calculator
Tap your station's size and what you'll plug in: see how long it lasts.
Device watts from a utility's sizing guide (EWEB) and Generac; the formula is Anker's. Free, and nothing you enter leaves this browser.
The formula
Hours = battery watt-hours x 0.85 / total watts. The 0.85 is Anker's allowance for efficiency losses on AC loads; its example is a 1,000 Wh station running a 100 W TV for about 8.5 hours. Add up everything running at the same time first.
- Watts versus watt-hours: the watt rating is the most the station can supply at once; the watt-hours are how much energy it stores, which sets the runtime.
- Cycling appliances such as refrigerators and CPAP machines switch on and off. Virginia Cooperative Extension says a refrigerator runs at full power about a third of the time it's plugged in, so the calculator counts a fridge at a third of its watts. The other devices count as running all the time.
- Startup surges matter for refrigerators, pumps and power tools: check that the station's surge rating covers them.
- Idle drain: turn off outputs you aren't using to stretch the battery.
More of the power outage kit
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How we built this
Every fact on this page comes from the sources listed below, read on . Where an organization doesn't publish a clear answer, we say so and tell you where to look instead of guessing.
- Anker SOLIX: How long will a power station last?
- Virginia Cooperative Extension: Estimating appliance and home electronic energy use (2020)
- EWEB (Eugene Water & Electric Board): Generator sizing considerations
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