Turbine Efficiency Calculator

Work out turbine efficiency instantly with clear inputs, formula shown and shareable results.

About Turbine Efficiency Calculator

Isentropic efficiency compares the actual enthalpy drop across a turbine with the ideal drop for a reversible adiabatic expansion to the same exhaust pressure. Power output is mass flow times actual enthalpy drop. Specific steam consumption, kilograms of steam per kilowatt-hour, is the practical performance index.

Formulas

Isentropic efficiency

Efficiency = (h1 - h2_actual) / (h1 - h2_isentropic)

Power

Power (MW) = mass flow (kg/s) x enthalpy drop (kJ/kg) / 1000

Worked example

With the default values below, Turbine Efficiency Calculator returns Isentropic Efficiency of 87.500%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Steam Flowminimum 0 t/hour: 300 t/hour
Inlet Steam Enthalpyminimum 0.01 kJ/kg: 3,400 kJ/kg
Actual Exhaust Enthalpyminimum 0.01 kJ/kg: 2,350 kJ/kg
Isentropic Exhaust Enthalpyminimum 0.01 kJ/kg: 2,200 kJ/kg

Results

Isentropic Efficiency: 87.500%
Power Output: 87.500
Actual Enthalpy Drop: 1,050.00
Specific Steam Consumption: 3.4286

Step by step

1Values used
2Isentropic efficiency
3Power
4Isentropic Efficiency= 87.500
5Power Output= 87.500
6Actual Enthalpy Drop= 1,050.00
7Specific Steam Consumption= 3.4286

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What efficiency is typical?

85-92% for a large multi-stage condensing turbine, 70-80% for small single-stage machines. Blade erosion, deposits and seal wear degrade it over time.

Why does exhaust pressure matter so much?

Lowering condenser pressure increases the available enthalpy drop substantially. A 10 mbar rise in back pressure can cost around 1% of output, which is why condenser cleanliness is closely monitored.