Free tool
What size generator do you actually need?
See the starting wattage your essential loads demand, then whether a battery, portable generator, or installed standby system fits the outage pattern before you compare products or sign an installer quote.
Choose your loads and outage pattern. Select what must stay running, then choose how long your outages usually last. No wattage or equipment lane is assigned from starter defaults.
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Choose my loadsYour sizing math
Choose your loads and outage pattern
Select what must stay running, then choose how long your outages usually last. No wattage or equipment lane is assigned from starter defaults.
Assumptions and sources
Reviewed July 12, 2026
Appliance figures are rounded planning inputs, not promises for your exact equipment. Replace them with the watts on each data plate. The model adds running loads, the largest motor-start surge, and 20% planning headroom.
The appliance wattages, 20% headroom, cost bands and generic fuel-use figures are Generator Guide editorial planning assumptions reviewed July 12, 2026. They are not model-specific consumption data or local quotes. Check the exact generator fuel chart, usable tank capacity and complete installer scope before relying on runtime or price.
- City of San Diego generator sizing guide explains adding running watts and motor startup needs for portable generators.
- Generac wattage worksheet documents the running-load plus largest-starting-load method and example appliance estimates.
- CPSC generator safety covers carbon monoxide, outdoor placement, and the danger of backfeeding.
Have a licensed electrician install any interlock or transfer switch. Never connect a generator to house wiring through a wall outlet.
Want the reasoning behind these numbers? Read the sizing guide, the real-cost guide, and before you run anything, the carbon monoxide rules.