Generator Fuel Consumption Calculator

About this calculator

A generator's fuel consumption rating is usually quoted at full load — the number of liters or gallons of diesel or gasoline it burns per hour when producing its rated kilowatt output. Actual burn rate falls as the load percentage drops, though not in a perfectly straight line, because an engine still needs fuel to idle its cylinders and alternator even with almost no electrical demand. This calculator applies the load percentage to the full-load figure and multiplies by the run time to give a practical estimate of total fuel used.

Electricians, event planners and site managers use this kind of estimate to size a fuel tank for a job, budget diesel costs for a multi-day power outage, or work out how often a portable generator needs refueling during a camping trip or construction shift. Knowing expected consumption also helps decide whether a smaller, more efficient unit running near its sweet-spot load would be cheaper to run than an oversized generator idling at low load.

Enter the generator's full-load fuel consumption, the percentage of that rated load it will actually run at, and how many hours it will run, and the calculator returns the estimated fuel burned for the job.