Generator Size for a Furnace
Size a generator for a furnace blower. Enter its running and startup watts to see the recommended size with surge headroom.
Runs locally in your browser — no upload, no trackingTry: Furnace blower running watts=800, Furnace blower startup (surge) watts=1800 → 800 W, 1,800 W, 2,160 W, 3.5 kW
How to use
A gas furnace itself uses little power, but the blower motor that pushes the heat draws about 800 running watts and surges to 1,800 on start. Size for the blower, not the burners. Enter your appliance's running and startup (surge) watts and press Calculate. The recommended size adds a 20% safety margin to the surge so the generator is never running at its limit.
These are typical figures — the plate on your furnace may read differently. If you run more than one device together, use the multi-appliance calculator instead.
FAQ
What size generator will run a furnace?
A furnace blower draws about 800 running watts and 1,800 starting watts. A 3 kW generator runs the blower; pair it with a fridge and sump pump and you are into the 5 kW range.