Steam boiler efficiency by the direct and indirect methods for gas, oil and coal: excess air from flue gas O2, every heat loss, fuel consumption, and the yearly fuel and cost saved by trimming excess air or stack temperature.
USD 39 one-time purchase
Download the sample report (PDF)
Need it once? Use it online: check your data free, unlock results from USD 9 for 3 runs.
What it does
Two methods to compare
Indirect (heat-loss) efficiency from the fuel analysis and flue gas, and direct efficiency from the metered fuel flow, with the difference flagged.
Gas, oil and coal
Fuel gas from composition in mol %, oil and coal from ultimate analysis, with HHV and LHV calculated or entered.
Excess air and flue gas
Excess air from flue gas O2 (dry or wet, CO corrected), air-fuel ratio, flue gas flow and composition and the water dew point.
Every heat loss
Dry flue gas, hydrogen and moisture in fuel, air moisture, CO, unburned carbon, radiation and blowdown, one by one.
Fuel and cost
Fuel consumption, steam-to-fuel ratio, CO2 emitted and the yearly fuel heat and cost.
What-if tables
Lower oxygen, cooler flue gas or both: new efficiency, fuel saved and money per year, with dew point checks.
Built for engineers
- Visible formulas — nothing hidden, so you can check every step.
- Fully referenced — methods from the standard references, checked against their published worked examples.
- Safe to share — sheets are protected against accidental edits, with an open password so you can still customise.
- Built-in input checks — clear warnings for impossible inputs and values outside typical ranges.
For engineering estimates; verify against site data. Code-based methods are aligned with the publicly documented procedure; they are not a licensed reproduction or a certification.
Preview the workbook
Real pages from the workbook with its built-in example loaded (example data, not a measured plant). Choose a page below, or select the large image to enlarge it.
Specification and checks
| Format | Excel workbook (.xlsx), no macros |
| Version | v1.0 |
| Works in | Excel 2010 or later, Windows and Mac |
| Units | SI, US and British, mixed freely |
| Includes | Guide tab with method and references, calculator, print-ready report |
| Checked against | 170 recalculated runs against an independent Python model (Cantera data, iapws steam package, element-balance solver): all 96 selector combinations, SI, US, British and industry units and 66 edge cases; largest deviation 0.0005 %. |
| Free version | Try the free boiler efficiency calculator |
Online tool or Excel workbook?
A free web calculator for the key figures of this topic is on the free calculator page.
| Online tool | Excel workbook (this page) | |
|---|---|---|
| What it does | The same sheet as the Excel workbook, run in your browser | Steam boiler efficiency by the direct and indirect methods for gas, oil and coal: excess air from flue gas O2, every heat loss, fuel consumption, and the yearly fuel and cost saved by trimming excess air or stack temperature. |
| Cost | Check your inputs free. Results: 3 runs for USD 9, or every online tool for USD 15 a month (USD 99 a year) | USD 39 once, yours to keep |
| Input checks and findings | Every input checked; findings with the unlocked results | Every input checked, with findings and recommendations |
| Report for your calculation file | Printable results sheet | Print-ready report with your plant, tag, document number, revision and sign-off |
| Formulas | Method described in the guide | Every formula visible in its cell |
| Save, edit and rerun your cases | Each run separately | Yes: keep and edit your own file |
| Works offline, on a plant PC | No, needs the internet | Yes: Excel 2010 or later, Windows and Mac |
Online access and the Excel workbook are separate licences: one does not include the other.
Compatibility, licence and support
| File | Excel workbook (.xlsx), no macros, version v1.0; works in Excel 2010 or later on Windows and Mac. Sheets are protected against accidental edits, with an open password so you can customise. |
| Licence | Single user. A team licence (up to 5 named users) is 3 × the shop price; site licences on request — licence terms. |
| Updates | Updates to this major version are included; download them again from the link in your receipt. |
| Support | Email [email protected] with your order number — questions on the method, your inputs or your results are welcome. |
| Refunds | If the tool does not work as described, or has an error we cannot fix, email [email protected] with your order number within 14 days of purchase and we will refund you in full. Refunds are not offered for a change of mind once a file has been downloaded. Read the full refund policy. |