Generator Fuel Cost by Load Calculator — See the Cost at Any Load
Estimate how much fuel a generator uses at a chosen electrical load and convert that fuel use into hourly, daily and annual operating cost.
Generator and fuel assumptions
Why generator fuel cost changes with load
A diesel generator consumes fuel even with little electrical output, while fuel consumption normally rises as electrical load increases. That makes fuel cost per useful kWh particularly important when comparing lightly loaded operation with higher utilization.
What the curve model does
The calculator begins with your no-load fuel rate and moves toward the full-load rate using the selected exponent. The curve is deliberately user-controlled instead of presenting a generic manufacturer curve as universal.
Why load percentage matters
A 500 kW generator operating at 20% load is not equivalent economically to a 100 kW generator operating at 100% load, even when the useful output is similar.
Worked example
At 65% load, a generator rated 500 kW produces a modeled 325 kW output. The entered fuel curve then estimates fuel use and cost at that operating point.
Practical use
Use the result to compare operating schedules, generator loading strategies or alternative unit sizes. Replace the approximation with project-specific fuel-curve data when making procurement decisions.
Limitations
Ambient conditions, fuel temperature, engine condition, auxiliary loads and transient operation can change real fuel consumption.
Frequently asked questions
Does the calculator include generator auxiliary loads?
Only if they are reflected in the fuel data you enter.
Can I use gallons instead of litres?
This version uses litres. Convert supplier data before entering it.
Does a lower fuel cost always mean better generator operation?
No. Reliability, loading limits, maintenance, redundancy and application requirements also matter.