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What size generator do I need?
Tick the appliances you want to keep running during an outage. We'll add up the running watts, account for motor starting surges, and suggest a standby-generator size.
Your estimate
- Running load
- 1,600 W
- Motor starting surge
- + 1,500 W
- Safety headroom (20%)
- × 1.2
Estimated need: 3.7 kW
Recommended size10 kW
This is a planning estimate from typical wattages, not a measurement of your home.
How this estimate works
- Running load. We sum the running watts of everything you selected, using typical values for common residential equipment.
- Starting surge. Motors (A/C, pumps, fridge compressors) draw extra power for a second or two when they start. We add the single largest motor's additional surge; motors rarely kick on at the exact same moment.
- Headroom. We add 20% so the generator isn't running flat-out, which is better for lifespan and leaves room for the things this list forgot.
- Round up. The result is rounded up to the next standard standby size (10–36 kW).
What this can't tell you
Real sizing depends on your actual appliances (check their data plates), whether you'll manage loads with a smart transfer switch, and local code. Two identical houses can need different sizes. Treat this as a solid starting point for a conversation, not the final answer.
Verify with a licensed electrician. Generator sizing, transfer switches, and installation are permitted electrical work in most jurisdictions. Have a licensed electrician confirm your load calculation before you buy.
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