Free online calculation of diesel generator (genset) power, energy and fuel consumptionpower energy generator calculation  diesel gas

Principle of diesel generator (DG)

The principle of thermal engine (or diesel engine or genset) electricity generation is quite simple. An electric thermal generator is a device that converts mechanical energy obtained from an external thermal source (fuel combustion) into electrical energy as the output.

Quick calculator of Diesel engine power

Enter your own values in the white boxes, results are displayed in the green boxes.

Calculate active and apparent electrical power of a genset:



Calculation of energy and fuel consumption of a diesel generator:

If you want to calculate energy and fuel cost associated to this active power, fill the time value below (number of hours and days the diesel engine is running) :


liter/kWh (see examples of fuel consumption rates)
Currency :
Cost of fuel :   per liter
Total amount of electricity bill :

Formula to calculate genset active and apparent power

How to calculate output power of a diesel engine? The simplest formula is :

Active power P = S * cosphi
Apparent power S = P / cosphi

   P = active electric power in output of the diesel generator in kW
   S = apparent electric power in output of the diesel engine in kVA
   Cosphi = power factor (usually between 0.8 and 1)

How to calculate output energy and consumption of a diesel engine? The formula is :

Energy in output : E = P*h*d (kWh)
Consumption of fuel : C = E*Ckwh (liter)

   E = active electric energy in output of the diesel engine in kWh
   P = active electric power in output of the diesel engine in kW
   h = number of hours per day the genset runs
   d = number of days the power generator runs
   Ckwh = Consumption of fuel per kWh (usual value is between 0.3 and 0.6 l/kWh)
   C = Consumption of fuel in liter

Excel file to calculate genset active and apparent power and fuel consumption

This excel file will help you to calculate power and electricity production according to load, fuel consumption and cost of kWh from diesel or gas generator.

Download Excel calculator for electric generator

Example of consumption per kWh consumption of a diesel generator at 75% of nominal power

Manufacturer Type Continious power COP (kW) Diesel consumption per kWh (l/kWh)
PRAMAC ES5000 5.4 kVA 4.3 0.51
SDMO SDMO T9HK 9 kVA 7.2 0.48
Caterpillar Model D100-6 125 kVA 90 0.3
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