Generator Fuel Consumption & Runtime Calculator

Estimate burn rate, tank runtime, and daily fuel use at any load

Enter fuel type, tank size, rated kW, and load percent (or actual kW). Get fuel burn, runtime at load, 50%/100% comparisons, and daily consumption — the runtime companion to generator sizing.

Also try our Generator Sizing Calculator and Generator Transfer Switch Calculator.

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Fuel Runtime vs Generator Sizing

The Generator Sizing Calculator answers “how big?” This tool answers “how long?” once you know rated kW and expected load. Runtime is tank size divided by burn rate; burn rate scales with load because engines are less efficient near full load.

Default Fuel Rates

Gasoline: 0.10 gal/kWh at half load, 0.15 at full load
Propane: 0.12 / 0.18 gal/kWh
Diesel: 0.08 / 0.12 gal/kWh
Natural gas: 0.09 / 0.14 therms/kWh (or pipeline unlimited)

Override the defaults when you have manufacturer fuel-curve data — portable inverter generators are often more efficient than open-frame units.

FAQ

Why does 50% load last longer than half of 100% runtime?

Specific fuel consumption (fuel per kWh) is usually better at partial load than at full load. Running at half load does not simply double runtime versus full load.

How should I enter propane tanks?

Use usable liquid gallons when possible. If you only know pounds, roughly divide by 4.2 for gallons of liquid propane.

What about natural gas pipeline?

Choose pipeline mode to see burn rate without a finite tank. Runtime then depends on maintenance intervals and load, not stored fuel.

Generator Fuel Consumption & Runtime Calculator

Recommended Electrical Tools

P3 Kill A Watt Electricity Monitor

Fluke 117 Digital Multimeter

Klein CL800 Clamp Meter

Fuel Runtime vs Generator Sizing

Default Fuel Rates

FAQ

Why does 50% load last longer than half of 100% runtime?

How should I enter propane tanks?

What about natural gas pipeline?

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