Energy
Boiler Efficiency Calculator
Calculate boiler efficiency from measured fuel input and useful steam or hot-water heat output.
Use the same fuel unit as the heating value below, such as kg/h for liquid or solid fuel, or Nm³/h for gas.
Use a heating value consistent with the efficiency basis being evaluated, typically LHV or HHV as required.
Use the steam-table enthalpy at the actual steam pressure and temperature.
Boiler Efficiency
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Useful thermal output divided by measured fuel-energy input.
Boiler efficiency
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Fuel energy input
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Useful heat output
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Estimated heat loss
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Heat loss fraction
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Fuel per tonne of steam
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Compare results only when fuel heating value, fuel measurement and useful heat output are on a consistent basis. HHV- and LHV-based efficiencies are not directly interchangeable.
Method:
Direct boiler efficiency is:
η =
Useful Heat Output ÷ Fuel Energy Input × 100
Fuel energy input is:
Fuel Input =
Fuel Consumption × Fuel Heating Value
For steam production:
Useful Heat =
Steam Flow ×
(Steam Enthalpy − Feedwater Enthalpy)
Feedwater enthalpy is approximated from:
hfw ≈
4.186 × Feedwater Temperature
in kJ/kg when temperature is entered in °C and the reference enthalpy is taken near 0°C.
For hot-water boilers:
Useful Heat =
Water Flow ×
cp ×
(Tout − Tin)
using a water specific heat of approximately 4.186 kJ/kg·K.
This is a direct or input-output efficiency calculation. It does not separately determine stack losses, excess-air losses, radiation losses, blowdown losses or unburned-fuel losses.
Steam enthalpy should come from an appropriate steam property table or process measurement for the actual pressure and temperature. Superheated steam must use the corresponding superheated-steam enthalpy.