Power Station & Generator Wattage Calculator

How the wattage calculator works

1. Select your appliances. Check the ones you'd want to keep running during an outage, or start from a quick preset (outage essentials, medical priority, or camping).
2. We add up running watts and the realistic starting-watts spike. Only one large motor (like a fridge or sump pump) typically starts at once — the calculator models that worst case, the same way generator manufacturers size their units.
3. You get a sized recommendation. The table below shows exactly which power station capacities fit your load, how long each would last, and the minimum generator rating if you'd rather go that route.

Running watts vs. starting watts: why both numbers matter

Every power station, portable generator and whole-house standby unit is rated for two different numbers, and mixing them up is the single most common sizing mistake. Running watts (also called rated or continuous watts) is what an appliance draws once it's already operating — a fridge humming along, a fan spinning at speed. Starting watts (also called surge or peak watts) is the short burst, usually under a second, that a motor needs to overcome inertia when it first kicks on. For a compressor-driven appliance like a refrigerator, sump pump or air conditioner, that surge can be two to three times the running figure.

A generator or power station that only covers your running-watts total will shut down, trip a breaker, or stall the moment a big motor tries to start. That's why this calculator doesn't just add up running watts — it finds the single highest-surge appliance in your selection and assumes it starts while everything else is already running, then sizes for that worst-case moment. It's the same conservative approach manufacturers use on their own sizing charts.

Power station vs. generator: which one do you actually need?

Portable power stations (roughly 300Wh to 5,000Wh+, built around LiFePO4 batteries from brands like Jackery, EcoFlow, Bluetti and Anker) are silent, produce zero exhaust fumes, and can be used indoors or in an apartment. They're the right fit for a fridge, Wi-Fi, medical devices, lighting and device charging — the small-to-medium loads that make up most outage priorities. Fuel-powered generators (portable or whole-house standby) cost less per watt at higher capacities and can run a well pump, central air conditioning, an electric water heater or a full HVAC system, but they need to run outdoors, require fuel storage, and whole-house units need professional installation with an automatic transfer switch.

A note on real-world runtime

The runtime estimates above assume your appliances draw their running watts continuously, which overstates real usage for anything that cycles — a fridge compressor, for example, typically runs 30-50% of the time rather than constantly. Treat the numbers here as a conservative floor: your actual runtime in daily use will usually be longer, not shorter.

⚠️ Wattage figures used in this calculator are typical industry averages for planning purposes, not a substitute for your appliance's own nameplate rating. For anything safety-critical — medical equipment, sump pumps, large motors — always confirm the exact wattage printed on the appliance itself before sizing your backup power.

Frequently asked questions