Pick what you need to keep alive and for how long. The answer is capacity in watt-hours, less about fifteen per cent for inverter losses, divided by the draw — and the arithmetic is printed with every result so you can put your own appliance’s label through it. It also checks the thing most calculators skip: whether the output can start a motor at all.
Pick what you need to keep alive and for how long. The answer is an estimate, not a measurement: that model’s watt-hours, minus 15% for inverter losses, divided by the draw we assume. The arithmetic is printed with every result so you can put your own numbers through it.
The label is usually on the back or inside the door. If it gives amps, multiply by 120 in the US.
Read these as estimates. The draw is a typical figure, not your appliance: a large American refrigerator and a small European one differ by a factor of two, and a compressor cycles on and off, so its average depends on the room temperature, how often the door opens and how old the seals are. We remove 15% for inverter losses; the real figure varies with load. And matching the running watts is not enough to start a motor: a fridge, a freezer, a sump pump or an air conditioner pulls roughly three times its running draw for the first instant, which is what the surge column is about. Check the label on your own appliance before you rely on any of this.
Watts is the output: what the station can deliver at any instant, and therefore what it can run at all. Watt-hours is the capacity: how much it holds, and therefore for how long. A large battery behind a small inverter will not start a refrigerator however long it could theoretically run one.
Anything with a motor — a fridge, a freezer, a sump pump, an air conditioner — asks for roughly three times its running draw for the instant it starts. That surge is what the “starts it” column checks, and it is a rule of thumb rather than a specification: if one specific appliance is the reason you are buying, read the surge from its own label.
The models in the table are one manufacturer’s, because their published capacities are the ones we have read and dated. The arithmetic is the same for any brand.
The full sizing method, or how long a battery runs a refrigerator.
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