⚡The Backup Power Guide
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Power Station Size Calculator: What Size Do I Need?

Pick the appliances you want to keep running during an outage, adjust the watts and hours, and get the capacity (Wh) and output (W) you need, plus matching models.

By The Backup Power Guide · Written by a solar installation & maintenance professional · Updated October 30, 2026
ApplianceWattsHours / dayStart W
0Capacity needed (Wh)
0Running watts if all on
0Peak with largest motor start

Math: Σ(watts × hours) × days ÷ 0.85 inverter efficiency. Wattages are typical estimates; check your appliance labels. Model specs come from each product's listing.

Short answer: Phones, lights and Wi-Fi for a day fit a 1,000 Wh power station. Add a refrigerator for a full day and most households land around 2,000–3,000 Wh, depending on the fridge (or a 1,000 Wh unit recharged with solar). Freezers, pumps, AC units and space heaters push you to 3,000 Wh+ home backup units.

Frequently asked questions

How do I calculate what size power station I need?

Add up watt-hours: running watts × hours of use for each appliance. Divide by about 0.85 to cover inverter losses, then multiply by the number of days you want to cover. The power station must also supply the total running watts of everything on at once, plus the starting surge of the largest motor.

Can a 1000Wh power station run a refrigerator?

Yes, for several hours to roughly half a day or more. A typical fridge compressor draws around 100–200 W while running and cycles on and off, so many fridges use roughly 1–2 kWh per day. Check your fridge label or Energy Guide sticker and use the fridge runtime calculator for your numbers.

Why does starting (surge) wattage matter?

Motors in fridges, pumps and AC units briefly draw several times their running watts when they start. If the power station cannot cover that surge, it will shut off even though the running watts look fine.

Are these appliance wattages exact?

No. They are typical estimates to get you started. The label on your appliance (watts, or volts × amps) is the number to trust.

Next: How long will my fridge run? · Best power stations for home backup

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