Heat of Combustion Calculator
Combine fuel quantity, heating value, and efficiency to evaluate released energy and usable output.
Use kilograms of fuel consumed.
Specify higher or lower heating value as needed.
Accounts for heat losses and incomplete combustion.
Total energy
105,000 kJ
Useful energy
94,500 kJ
Useful energy (kWh)
26.25 kWh
How to Use This Calculator
Determine fuel quantity
Measure the mass of fuel consumed during the combustion process.
Look up heating value
Use tabulated higher or lower heating values for the fuel and operating moisture content.
Estimate efficiency
Account for burner, boiler, or engine efficiency to capture real usable output.
Review calculated energy
The calculator multiplies mass and heating value, then scales by efficiency and converts to kilowatt-hours.
Formula
Energy = mass * heating value
Useful energy = mass * heating value * efficiency / 100. Convert to kWh by dividing kilojoules by 3600.
Example
Burning 2.5 kg of fuel with 42000 kJ/kg and 90 percent efficiency delivers 94500 kJ, equal to 26.25 kWh.
Full Description
The heat of combustion measures the energy released when fuel burns completely. Practical systems experience losses, so useful output is lower than theoretical energy.
Knowing both values supports sizing boilers, engines, and heat recovery units, and helps compare fuel options on an energy basis.
Frequently Asked Questions
What is the difference between HHV and LHV?
Higher heating value includes condensation of water vapor; lower heating value assumes exhaust water stays vapor. Choose the one that matches your system.
Can I use volume instead of mass?
Convert volume to mass using fuel density before using this calculator.
How does moisture affect heating value?
Moisture lowers effective heating value because energy goes to evaporating water. Use data for the actual moisture content.
What if efficiency is unknown?
Start with an estimate from equipment manuals or leave efficiency at 100 percent to see theoretical energy.
Why report kWh?
Electrical output and many utility bills use kilowatt-hours, making it useful for comparing against electricity consumption.