Calculation sequence
Step-by-step method
- Calculate water temperature rise.
- Calculate water-side output with the entered fluid factor.
- Divide output by fuel input and compare with the entered reference efficiency.
CommissioningIntermediateCentral Plant
Boiler Efficiency Verification Calculator
Estimate boiler thermal efficiency from fuel input and measured water-side output.
Why it matters: A transparent input-output balance helps identify mismatched meters, unstable firing, flow error, and test-boundary concerns.
Calculated result
Engineering evaluation
Calculated input-output efficiency (η)83.33 %
- Calculated water-side output (Qout)
- 2.5 MMBtu/h
- Water temperature difference (ΔT)
- 10 °F
- Difference from reference efficiency (δη)
- -1.667 percentage points
- Unaccounted input-output difference (Qloss)
- 0.5 MMBtu/h
Engineering interpretation
The input-output balance indicates 83.33% efficiency, -1.667 percentage points from the entered 85% reference. Confirm fuel heating-value basis, meter timing, stable firing rate, and the complete thermal boundary.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
ΔT = Tl−Te
Qout = FVΔT/1000000
η = Qout/Qin×100
δη = η−ηd
Qloss = Qin−Qout
within entered criterion when |δη| ≤ T
Current substitution
Qout = 500×500×10/1000000 = 2.5 MMBtu/h; η = 83.33%; δη = -1.667 points.
Equation legend
Inputs and calculated quantities
- Qin
- Measured fuel input — MMBtu/h or kW
- V
- Measured water flow — gpm or L/s
- Te
- Entering water temperature — °F or °C
- Tl
- Leaving water temperature — °F or °C
- F
- Fluid heat-transfer factor — Btu/(h·gpm·°F) or kJ/(L·K)
- ηd
- Approved reference efficiency — %
- T
- Authorized efficiency tolerance — ± percentage points
- η
- Calculated input-output efficiency — %
- Qout
- Calculated water-side output — MMBtu/h
- ΔT
- Water temperature difference — °F
- δη
- Difference from reference efficiency — percentage points
- Qloss
- Unaccounted input-output difference — MMBtu/h
Applications
How this calculation is used
Building design
Check scheduled input, output, and efficiency relationships.
Construction
Evaluate startup metering and stable-load test data.
Commissioning
Compare measured thermal efficiency with an approved reference and tolerance.
Quality controls
Assumptions and limitations
Assumptions
- Entered values represent the same stable operating condition.
- Measurements and reference values use consistent units and boundaries.
Limitations
- This is a screening and field-verification tool, not an automatic acceptance decision.
- Project criteria, manufacturer data, governing standards, and measurement uncertainty remain controlling.
Field use
Verification procedure
- Confirm the approved reference values and test boundary.
- Stabilize the system and record calibrated field measurements.
- Review calculation assumptions, uncertainty, and supporting evidence before disposition.
Common engineering mistakes
- Comparing readings taken at different loads, modes, or reference conditions.
- Treating a calculated status as proof of code, contract, or manufacturer compliance.
Technical basis
References and source standards
- U.S. Department of Energy—Industrial Assessment and System ResourcesFederal technical resources for fan, pump, motor, boiler, chiller, and energy-system performance evaluation.
- ASHRAE Handbook—FundamentalsCurrent handbook chapters covering fluid flow, thermodynamics, psychrometrics, measurement, and engineering analysis; the project reviewer must verify the licensed edition used for approval.
- ASHRAE Commissioning ResourcesCommissioning-process context for defining test methods, acceptance criteria, evidence, and owner requirements.
Engineering calculation disclaimer
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
Read the full use and limitation statement