Portable Generator Fuel Consumption and Runtime Planning
Estimate gallons per hour and tank runtime from load watts and manufacturer fuel curves.
Generators are sold on peak watts and tank size. Outages ask a different question: how long will this tank last at my actual load? Answer that with fuel consumption at load, not brochure extremes.
Rated vs. real load
A 3,500 W unit does not burn full fuel at 400 W of fridge and lights. Consumption scales roughly with electrical load—often quoted in gallons per hour at half and full load in manuals.
Runtime math
Runtime = tank gallons ÷ consumption gal/hr at your load. If you do not know partial-load consumption, assume something between idle and full spec—many owners use seventy percent of full-load rate as a guess until they test.
Safety and sizing
Never run portable units indoors. Match starting surge for motors—well pumps win the sizing fight, not LED bulbs.
Fuel storage reality
Gasoline ages; rotate stored fuel with stabilizer. Propane models trade tank swap convenience for energy density math. Log hours per outage to refine next year's storage plan.
Generators reward conservative planning. Test once under real loads, record gal/hr, and you will never guess tank life during a storm again.