Generator Sizing Calculator
Choose the appliances you need to keep running during an outage and get a recommended backup generator size that covers both continuous load and startup surge.
Appliances to Power
Recommended Size
Recommended Generator Size
Total Running Watts
Peak Surge Watts
Sizing Note
Sizing your generator...
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Select the appliances you want to run to see a recommended generator size
How Generator Sizing Works
Running vs. Surge Watts
- • Running (rated) watts are the continuous power a device needs
- • Surge (starting) watts are the brief spike when a motor kicks on
- • Motors like pumps and compressors surge well above their running draw
- • Usually only one large motor starts at a time
How We Size It
- • Add up the running watts of everything you select
- • Add the single largest startup surge on top of that
- • Include roughly 20% headroom so the generator is not maxed out
- • Round up to a common generator size
Wattage presets are typical estimates. Check the nameplate on your own appliances for exact figures, and consult a licensed electrician before connecting a generator to your home.
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