Cogeneration Savings Calculator

Work out cogeneration savings instantly with clear inputs, formula shown and shareable results.

About Cogeneration Savings Calculator

Cogeneration efficiency is electricity plus useful heat divided by fuel input, commonly 75-85%. The meaningful measure is primary energy saving: the fuel a separate power station at 50% efficiency and a boiler at 85% would need, less the fuel the cogeneration plant actually uses. Savings of 10-25% are typical.

Formulas

Overall efficiency

Efficiency = (electrical output + useful heat) / fuel input

Primary energy saving

PES = 1 - fuel used / (electricity / reference power efficiency + heat / reference boiler efficiency)

Worked example

With the default values below, Cogeneration Savings Calculator returns Overall Cogeneration Efficiency of 85.714%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Electrical Outputminimum 0 MW: 5 MW
Useful Heat Recoveredminimum 0 MW thermal: 7 MW thermal
Fuel Inputminimum 0 MW thermal: 14 MW thermal
Boiler Efficiency If Heat Made Separatelyaccepts 1–100 %: 85 %

Results

Overall Cogeneration Efficiency: 85.714%
Primary Energy Saving: 23.226%
Fuel Saved: 4.2353
Fuel For Separate Generation: 18.2353

Step by step

1Values used
2Overall efficiency
3Primary energy saving
4Overall Cogeneration Efficiency= 85.714
5Primary Energy Saving= 23.226
6Fuel Saved= 4.2353
7Fuel For Separate Generation= 18.2353

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

Why must the heat be useful?

Heat that is rejected to atmosphere does not count. Cogeneration only saves energy where there is a genuine, coincident heat demand — a plant sized for electricity with no heat sink is just an inefficient power station.

Does cogeneration qualify for incentives?

Many jurisdictions certify high-efficiency cogeneration against a primary energy saving threshold, often 10%. Certification usually requires metered electricity and heat data.