Boiler Thermal Efficiency (Direct Method)

Direct method: useful heat output divided by fuel energy input.

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Formula

η = output ÷ input × 100

Example calculation

170,000 out ÷ 199,000 in → 85.4%.

Practical HVAC use

Commissioning and performance tracking.

Common mistakes

Using nameplate rather than measured values.

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Educational tool. Results are estimates from the stated formulas; always confirm with manufacturer data and the code adopted in your jurisdiction. All calculators