Boiler Efficiency Calculator | Thermal Efficiency, Heat Output, Fuel Consumption

📖 How to Use This Boiler Efficiency Calculator

Enter steam output – The mass flow rate of steam produced in kg/h.

Enter steam enthalpy – The enthalpy of the produced steam (kJ/kg). Saturated steam at 10 bar ≈ 2778 kJ/kg.

Enter feedwater enthalpy – The enthalpy of the feedwater entering the boiler (kJ/kg). At 20°C ≈ 84 kJ/kg.

Enter fuel consumption – The mass flow rate of fuel burned in kg/h.

Select fuel type – Choose from common fuels or enter a custom heating value.

🔥 Understanding Boiler Efficiency

Boiler thermal efficiency is the ratio of useful heat output (heat absorbed by the water/steam) to the heat input from the fuel. It indicates how effectively the boiler converts fuel energy into useful steam energy.

The calculation formula is:

η = (ṁₛ × (hₛ - h_fw)) / (ṁ_f × LHV) × 100
where ṁₛ = steam mass flow (kg/h), hₛ = steam enthalpy (kJ/kg), h_fw = feedwater enthalpy (kJ/kg), ṁ_f = fuel mass flow (kg/h), LHV = lower heating value (kJ/kg).

Typical boiler efficiencies: 75-85% for industrial boilers, 85-92% for modern condensing boilers.

💡 Practical Applications

Power plants – Steam generation and efficiency monitoring.
Industrial heating – Process heating and steam systems.
Energy audits – Assess and optimize boiler performance.
Environmental compliance – Reduce fuel consumption and emissions.
Cost reduction – Identify efficiency improvement opportunities.

❓ Frequently Asked Questions (FAQ)

What is boiler thermal efficiency?

Boiler thermal efficiency is the percentage of fuel energy that is converted into useful heat. It is calculated as (heat output / heat input) × 100.

What is the difference between LHV and HHV?

LHV (Lower Heating Value) excludes the latent heat of vaporization of water in combustion products. HHV (Higher Heating Value) includes it. This calculator uses LHV, which is more relevant for boiler efficiency.

What is a good boiler efficiency?

Modern condensing boilers can achieve 90-95% efficiency. Standard industrial boilers typically achieve 75-85%. Higher efficiency means lower fuel costs and emissions.

What causes boiler efficiency losses?

Major losses include: flue gas heat loss (most significant), radiation loss, convection loss, and incomplete combustion. Proper maintenance and optimization can reduce these losses.

How do I improve boiler efficiency?

Install heat recovery systems, reduce excess air, tune the burner, insulate surfaces, reduce blowdown, and use economizers to preheat feedwater.

What is the effect of feedwater temperature on efficiency?

Higher feedwater temperature reduces the heat required to produce steam, increasing efficiency. Each 6°C increase in feedwater temperature improves efficiency by approximately 1%.