Work out boiler efficiency instantly with clear inputs, formula shown and shareable results.
The direct or input-output method compares the heat absorbed by the steam with the heat released by the fuel. Steam flow times enthalpy rise is the useful output; fuel flow times gross calorific value is the input. The gap is the sum of stack, blowdown, radiation and unburnt losses.
Direct method efficiency
η = steam flow x enthalpy rise / (fuel flow x GCV) x 100
η = steam flow x enthalpy rise / (fuel flow x GCV) x 100. The direct or input-output method compares the heat absorbed by the steam with the heat released by the fuel.
When fuel or steam metering is unreliable. The indirect method adds up measurable losses instead, which also shows which loss to attack.
This calculator takes 4 inputs: Steam generated, Enthalpy rise, feedwater to steam, Fuel consumption, Fuel gross calorific value. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.