Generator Runtime Calculator
Estimate generator runtime, usable fuel, delivered electrical energy and operating cost from tank size and measured fuel consumption.
Default project preview
9.6 hours
Delivered energy per usable tank
43.2 kWh
Fuel cost per hour
$2.81
Usable-tank fuel cost
$27.00
Fuel for planned period
9 gal
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Fuel tank capacity
Enter this project assumption in gal. The current imperial default is 8 gal.
Fuel reserve
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Fuel consumption at planned load
Enter this project assumption in gal/hour. The current imperial default is 0.75 gal/hour.
Average delivered electrical load
Enter this project assumption in kW. The current imperial default is 4.5 kW.
Fuel price
Enter this project assumption in per gal. The current imperial default is 3.75 per gal. Minimum: 0.
Planned operating period
Enter this project assumption in hours. The current imperial default is 12 hours.
How to read the outputs
Delivered energy per usable tank
4.5 kW average load. Default preview: 43.2 kWh.
Fuel cost per hour
consumption × entered fuel price. Default preview: $2.81.
Usable-tank fuel cost
7.2 gal. Default preview: $27.00.
Fuel for planned period
12 operating hours. Default preview: 9 gal.
Usable tanks for plan
rounded up. Default preview: 2.
Fuel reserve
not included in usable fuel. Default preview: 10%.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Usable fuel = tank capacity × (1 − reserve). Runtime = usable fuel ÷ fuel consumption per hour. Delivered energy = runtime × average electrical load. Operating cost uses fuel consumption and price.
Related tools
Continue planning the project
FAQ
Generator Runtime Calculator questions
Why enter fuel consumption instead of only generator size?+
Generators of the same rating can use different amounts of fuel, and consumption changes substantially with load.
What reserve should be used?+
A reserve accounts for unusable fuel, gauge uncertainty and avoiding a completely dry tank. Use a value appropriate to the equipment.
Does this calculate safe generator capacity?+
No. Use a generator-sizing and electrical-load calculation to verify starting loads, continuous rating and connection method.