Your generator
Your estimate
How does generator fuel consumption work?
Generators burn fuel based on how much power they actually deliver, not their rated size. A 7,500W generator running at 50% load delivers 3,750W and burns roughly half of what it would at full load.
We estimate hourly fuel use by multiplying your active load (in kW) by a fuel-rate constant for your fuel type. These are typical values observed across common home generators:
| Fuel type | Rate per kW per hour | Notes |
|---|---|---|
| Gasoline | ~0.14 gal/kWh | Standard for portables |
| Diesel | ~0.08 gal/kWh | Most efficient |
| Propane | ~0.18 gal/kWh | About 0.75 lb/kWh |
| Natural gas | ~12 ft3/kWh | Whole-home units |
Rates are typical at 50% load. Efficiency drops slightly at very light loads and improves near the generator's efficient operating range. Your unit's manual is the most accurate source.
How long will a generator run on a tank of fuel?
A 5,000W gasoline portable at 50% load (2,500W active) uses about 0.35 gal/hr, which means a 5-gallon tank runs roughly 14 hours. A 400-lb propane tank holds about 94 gallons, and a tank is filled to roughly 80% of that. On a 12kW standby at 50% load (6kW, about 1.1 gal/hr at these rates) that is roughly 3 days of continuous running. Runtime drops fast as you add load.
What if you need to run longer than one tank?
If your runtime math tells you the outage will outlast one tank, the practical fix is either a bigger tank or an efficient dual-fuel unit that also runs on propane, which stores indefinitely. These are common size brackets, matched to the load figures in the wattage chart.
- Westinghouse 7500 Peak EFI Dual Fuel (EFI cuts fuel use, runs gas or propane)
- DuroMax XP13000HX Dual Fuel (large portable, longer runtime at low load)
- Generac 14kW Whole Home (standby, runs on natural gas with no refueling)
As an Amazon Associate I earn from qualifying purchases. Sizing comes first: use the calculator to confirm the watts you need, then compare models in that bracket. Verify rated running watts against the nameplate before buying.
More tools and guides
Explore the rest of the generator toolkit:
- Solar generator size calculator (battery Wh for camping, RV & blackouts)
- Generator size calculator (what size do you need?)
- Generator wattage chart (running & starting watts for home appliances)
- Portable vs standby generator (which should you buy?)
- What size generator for a well pump? (1/2 HP and 1 HP, plus the 240 volt catch)
- What size generator for a sump pump? (1/2 HP and 1 HP, and why storms are worst)
- What size generator for a refrigerator and freezer? (startup watts plus food safety time)
- What will a 7,500 watt generator run? (a full worked example)
Disclaimer: This is an estimate for planning purposes only. Actual fuel consumption varies by generator make, model, engine efficiency, altitude, and ambient temperature. Your generator's owner's manual is the authoritative source for its fuel consumption. Never run a generator indoors.