How accurate is this estimate?

The calculator uses published consumption factors for each fuel type at a given load. Real-world consumption can vary ±10–20% depending on generator age, altitude, temperature, and how stable the load is. Use the result as a planning estimate, not a guarantee.

What load percentage should I use?

Most generator manufacturers rate consumption at 50% and 100% load. Running at 50–75% load is common for residential backup use. Running continuously at 100% increases wear and raises fuel consumption significantly. For conservative budgeting, use 75%.

How does fuel type affect consumption?

Gasoline generators typically consume about 0.50 gallons per hour per kilowatt at full load. Diesel is more efficient — roughly 0.40 gal/kWh. Propane burns cleaner but has lower energy density, consuming about 0.65 gal/kWh equivalent. Prices also differ, so the cheapest fuel per gallon is not always the cheapest to run.

My generator is rated in kVA, not watts. What do I enter?

Multiply kVA by the power factor (typically 0.8 for most generators) to get kW, then multiply by 1000 to get watts. For example, a 10 kVA generator at 0.8 PF = 8 kW = 8000 watts.

Does idle consumption differ from loaded consumption?

Yes. Generators at very low loads (under 25%) can be less fuel-efficient per watt of output because the engine still burns fuel to run itself. The calculator applies a mild efficiency penalty below 25% load to reflect this.

Generator Fuel Consumption Calculator

Name: Generator Fuel Consumption Calculator
Availability: InStock
Author: Nham Vu

Enter your generator's rated wattage, load percentage, fuel type, and run hours to estimate fuel use per hour and total running cost.

Generator Settings

Rated Wattage (W)

Check your generator label or manual. Enter kVA × 800 if rated in kVA.

Load Percentage: 75%

10% (light) 50% (typical) 100% (full)

Fuel Type

Units:

Fuel Price ($/gal)

Run Time (hours)

Results

Consumption / hr

—

gal/hr

Total Fuel

—

gallons

Total Cost

—

USD

Parameter	Value
Effective load	—
Power draw	—
Fuel type	—
Base rate (full load)	—
Adjusted rate	—
Run time	—
Cost per hour	—

Estimates use published consumption factors: gasoline 0.50 gal/kWh, diesel 0.40 gal/kWh, propane 0.65 gal/kWh at full load. Actual usage varies by generator model, altitude, and ambient temperature. Use as a planning guide.

Summary

Enter your generator's rated wattage, load percentage, fuel type, and run hours to estimate fuel use per hour and total running cost.

How it works

Enter your generator's rated wattage (found on the label or manual).
Set the load percentage — how hard the generator is actually working (50–75% is typical for continuous use).
Select your fuel type: gasoline, diesel, or propane.
Enter your local fuel price per gallon (or liter if you switch units).
Enter how many hours you plan to run the generator.
Read the estimated fuel consumption per hour and total cost.

Use cases

Budget fuel for a camping trip or outdoor event with a portable generator.
Estimate running costs during a power outage before buying a standby generator.
Compare gasoline vs diesel vs propane running costs for the same generator size.
Plan fuel reserves for a job site generator running multiple shifts.
Calculate monthly operating costs for a backup generator on a business property.
Determine how long a full fuel tank will last at a given load.

Frequently Asked Questions

Last updated: 2026-07-04 · Reviewed by Nham Vu