What size generator runs a furnace?

Use the about 2,200 W inverter class as the starting estimate for Furnace blower, 1/2 HP.

Running 800 W + largest start delta 800 W = 1,600 W peak. Add 25% headroom: 2,000 W.

Sizing estimate only - confirm with a licensed electrician; never backfeed a panel.

Loads used

Load	Running W	Starting W	Note
Furnace blower, 1/2 HP	800	1600	estimated 2x blower start

Models in this class

Honda EU2200i

1,800 running / 2,200 starting W. gasoline.

official Honda technical specifications list 2200 W max and 1800 W rated

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WEN 56235i

1,900 running / 2,350 starting W. gasoline.

official WEN page lists 2350 surge watts and 1900 rated watts

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Champion 201317

1,850 running / 2,500 starting W. gasoline.

current 2500 W Champion inverter used as successor-class substitute for 100692

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Why the estimate can change

Use nameplate watts when available. Pumps, compressors, altitude, fuel type, and extension-cord voltage drop can all change the practical generator size.