What size generator do I need?
Add everything you want to run at the same time. We total the running watts, add the single largest motor-start surge, and apply a 20% headroom margin — the same method as Generac's official sizing worksheet. Then we show which battery power stations cover the same list, and for how long.
Your appliance list
How this number is built (assumptions, with grades):
• Appliance watts come from Generac's official Wattage Worksheet, Generac owner's-manual wattage charts, and Home Depot's sizing guide — each row on our wattage chart names its source. Where sources conflict, we do not average them; the chart shows the conflict. CONFIRMED (primary sources).
• Only one motor is assumed to start at a time, while everything else is already running — Generac's worksheet rule. CONFIRMED (method as published).
• The ×1.20 headroom follows the common sizing guidance also printed by Generac (add 20% for safety margin and future loads). REPORTED.
• Runtime estimates use our standard 0.85 AC efficiency assumption — see how we calculate. REPORTED (Bluetti's published runtime formula uses the same 0.85 factor).
More backup-power calculators
Pick any of 30 power stations, add your loads, get hours — with a motor-start check.
How long will it run my fridge? →Duty-cycle aware: a fridge's compressor only runs part of the time.
CPAP runtime calculator →Hours and nights per charge for your device's wattage. Device runtime only — no medical claims.
Solar charging time →How long your panels really take, with the 0.78 real-world derate and your station's input cap.
Appliance wattage chart →Running and starting watts for 65 appliances, every row sourced.
Power station runtime pages →Specs and runtime tables for 30 models, from manufacturer data only.
Generator sizing questions
What size generator do I need for a refrigerator?
A fridge draws roughly 600–800 running watts by Generac's worksheet figure (700W) and needs up to about 2,200 additional watts for a split second when its compressor starts. Any generator or power station rated above ~1,000W continuous with surge headroom above ~2,900W starts one comfortably. Runtime is a different question — see the fridge runtime calculator.
Why do starting watts matter more than running watts?
Motors (fridges, pumps, saws, air conditioners) draw 2–3× their running watts for a moment at startup. A unit that covers your running total but not the start peak will trip the instant a compressor kicks on. Our calculator checks both, and refuses to print a runtime for a load a model can't start.
Can a battery power station replace a generator for home backup?
For essentials — fridge, lights, phones, laptop, CPAP — yes, for hours to a day or two depending on capacity, and silently with no fuel. For central AC, electric water heaters, dryers, or multi-day outages without solar, a fuel generator or a whole-home system is the honest answer. Our sizing results say so when your list outgrows every battery model in the database.
WattLong is reader-supported. Some links on this site are affiliate links: if you buy through them, we may earn a commission at no extra cost to you. See our affiliate disclosure. All results are estimates — verify with the manufacturer and a licensed electrician before relying on them.