Power Station Sizing Calculator
Tell the calculator which appliances you want to keep running and for how long. It adds up the real watt-hours — allowing for how often each device actually cycles, plus inverter and battery losses — and gives you a usable-capacity range, the inverter rating to look for, and power stations that fit. No email, no sign-up.
How it works
Every device on the list carries a real running-wattage figure and a duty cycle: the share of each hour it actually pulls power. A fridge, for instance, runs closer to a third of the time, not constantly, so planning as if it ran flat out overshoots by a lot.
The calculator multiplies watts by that duty cycle across the hours you choose, adds the energy lost turning battery DC into household AC, and keeps a safety reserve so you're not planning down to the last watt. That total is your usable watt-hour range.
Motors — pumps, compressors, microwaves — spike well above their running watts for a moment when they start. The tool flags the surge rating your inverter needs to cover, so a station doesn't trip the instant the fridge kicks on.
Frequently asked questions
How many watt-hours do I need to run a refrigerator during an outage?
A typical full-size fridge draws about 100–200 running watts but only cycles roughly a third of the time, so it uses close to 1–2 kWh over a full day. Keeping it cold for 24 hours usually means a station in the 1,000–2,000 Wh range, more once you add other devices. Pick your fridge above to get a number for your exact plan.
What size power station do I need for my whole house?
Whole-home backup is a different job from keeping essentials alive. Most people size for a short list — fridge, a few lights, phones, maybe a CPAP or sump pump — which lands in the 1–3 kWh range. Running central air, electric heat, or a well pump pushes you toward a generator or a large expandable system. This calculator is built for the essentials case.
Do I need to plan for surge watts, or just running watts?
Both. Running watts decide how long the battery lasts; surge watts decide whether the station can start the device at all. Anything with a motor briefly pulls two to three times its running watts. If the inverter's surge rating is too low, it shuts off instead of starting the appliance, so the calculator shows both numbers.
How accurate is the estimate?
It's a planning range, not a guarantee. Real draw shifts with temperature, battery age, how full your fridge is, and the exact model. We round up and add reserve on purpose, so the honest reading is "buy at least this much," not "this precise number."