Boiler Efficiency Calculator

Estimate Boiler Efficiency

Compare useful heat output with fuel input, or assess heat-loss performance

Use the direct method for steam or hot-water output, or the indirect method to estimate efficiency by subtracting measured heat losses. This is intended for preliminary energy assessment.

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Boiler Efficiency Calculator

Direct and Indirect Boiler Efficiency Assessment

Choose the direct method to compare useful heat with fuel energy, or the indirect method to identify the losses reducing efficiency.

Choose the assessment method that matches your available data

Direct method uses steam or hot-water output and fuel input. Indirect method sums individual heat losses, helping identify the most important improvement opportunity.

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Customer and Boiler Details

Customer / company name * Contact person * Email * Phone number * Boiler type *

Calculation Method

Direct Method Useful heat output divided by fuel energy input. Indirect Method 100% minus the total measured heat losses.

Boiler Output Type

Steam Use steam and feedwater enthalpy values. Hot Water Use water flow and temperature rise.

Selected method

Direct Method â€” Steam

Calculates efficiency from useful steam heat output compared with fuel energy input.

Boiler Efficiency (%) = [Steam Flow Rate Ã— (Steam Enthalpy âˆ’ Feedwater Enthalpy)] Ã· [Fuel Flow Rate Ã— Fuel Calorific Value] Ã— 100

Steam Output Data

Steam flow rate * Steam flow unit * Steam enthalpy, kJ/kg * Feedwater enthalpy, kJ/kg *

Fuel Energy Input

Fuel flow rate * Fuel flow unit * Fuel calorific value * Calorific value unit *

Select matching fuel flow and calorific value units: mass with mass, volume with volume, or NmÂ³ with NmÂ³.

This calculator provides an estimated boiler efficiency for preliminary energy assessment. For official energy audit reporting, use verified site measurements, calibrated instruments, fuel analysis, steam table data, and applicable standards or guidelines.

Need a Detailed Boiler Assessment?

DW Energy and Engineering can help verify fuel use, steam conditions, combustion performance, heat losses, and practical boiler efficiency opportunities.