How Much Fuel Does a Standby Generator Use?

A Generac 22kW model G007325-0 is listed at 2.45 gallons of propane per hour at half load and 3.71 gallons at full load. On natural gas, the published figures are 221 and 311 cubic feet per hour. Those are model-specific reference points, not a prediction for every house. The same “22kW” label on a different generator can come with different fuel requirements. Generac publishes these figures in the G0073250 specifications.

Published fuel consumption for four Generac models

The table below uses Generac specification sheet A0005151077, Rev. D, dated August 13, 2026. Model numbers identify the transfer-switch bundles; the figures apply to the generator configurations covered by that sheet. LP means propane. Natural-gas figures are cubic feet per hour, not gallons.

Source: Generac 22–28kW specification sheet, page 4. Half load means half of the applicable fuel-specific output rating. Different rows therefore represent different electrical loads; this is not an equal-output efficiency test. For example, the 22kW model is rated at 21kW on natural gas, so its NG half-load point is 10.5kW.

What that means over a day

Multiply an hourly fuel rate by the hours spent at that load. For the G007325-0 on propane, a hypothetical 24 hours at half load gives 2.45 × 24 = 58.8 gallons. At full load, the arithmetic is 3.71 × 24 = 89.04 gallons.

On natural gas, those two reference calculations are 221 × 24 = 5,304 cubic feet and 311 × 24 = 7,464 cubic feet. They show scale. They do not establish a minimum, maximum, or expected bill for your home.

A more useful planning example splits the day: 16 hours at the published half-load rate plus 8 hours at full load would use (16 × 2.45) + (8 × 3.71) = 68.88 gallons of propane. This is an illustrative load schedule, not measured household performance. Real HVAC and pump loads cycle, and actual consumption at intermediate loads requires better data than a two-point table.

Why an older 22kW figure may be different

Generac’s older Guardian sheet lists the G007043-10 at 2.53 and 3.90 gallons of propane per hour, and 228 and 327 cubic feet of natural gas per hour, at half and full load respectively. The Guardian specification sheet, page 4, covers that equipment. Keep the model suffix and document revision with any number you use; do not mix those figures into a newer-model estimate.

Turn the calculation into a fuel plan

Write down the appliances you intend to run and when: overnight heating, daytime cooling, well-pump operation, cooking, and optional loads. Then prepare a modest-use case and a heavier-use case. Reducing appliance use can lower total demand, but delaying a load without reducing its eventual use does not guarantee a particular fuel saving.

For propane, compare the estimate with the fuel actually available above your supplier’s refill reserve, allowing separately for other gas appliances. The propane tank sizing guide works through that calculation. For natural gas, ask the installer and utility to confirm full-load delivery capacity; an average daily estimate cannot size a gas pipe.

Bring your model number, fuel type, and expected outage loads to Brite Generators at 270-223-6302. Those details make a fuel estimate useful before you commit to equipment or a tank.