How we calculate

The calculator uses three numbers per appliance and two per power station. Here is every one of them.

Energy: how big the battery must be

For each item: average draw (W) × hours. We add them up, subtract any solar top-up, then divide by 0.85 for inverter losses. Example: a fridge at 60 W average for 6 hours is 360 Wh; ÷ 0.85 = 424 Wh of battery.

Output: what it can run at once

We add the running watts of everything you picked, then add the biggest start-up spike on top. A station qualifies only if its continuous output covers the running total and its surge rating covers the spike. Where a manufacturer doesn't state a surge rating, we use its continuous rating, which is the safe assumption.

Solar

If you tick solar, we assume a 200 W panel puts back about 700 Wh on a sunny day, for each full day of your plan. Cloudy days give less.

Picks

• Our pick: the smallest station that covers your whole plan with a 10% margin (batteries lose a little capacity with age and in the cold) and can start everything on it. If that model is sold out we pick the next one up.
• Spend less: a smaller station from another brand that covers at least half your hours.
• Room to grow: a larger station from another brand with at least 15% more battery.
• Above about 4,200 Wh we recommend a generator instead, because it costs less for loads that size.

Appliance values

Typical figures. Your own device's label is better: check the watts on the plug or nameplate.

Power stations we compare

Specs from each manufacturer's own product page, checked 16 October 2026. Stock changes often; discontinued models are removed.

Generators

For the generator sizer we add up the running watts of everything you want on at the same time, then add the single biggest start-up extra (starting watts minus running watts) on top, because motors start one at a time. That is the standard sizing rule Generac publishes. A generator qualifies when its running watts cover the total with a 10% margin and its starting watts cover the peak, on the fuel you chose (propane ratings are lower). If anything on your list usually runs on 240 V, only generators with a 120/240 V outlet qualify.

Water and food

Water: 1 gallon per person per day (Ready.gov), doubled for very hot weather. Food: 2,000 calories per adult per day (the FDA label basis) and 1,400 per child (our assumption). The Red Cross recommends 3 days to evacuate and 2 weeks at home.

What we don't do

We haven't bench-tested these models ourselves; every figure is the manufacturer's published spec run through the maths above. We don't print prices, because they change often; the retailer's page always shows the current one.