✅ – Clear boundary definition, reference temperature (usually 77°F or 59°F depending on fuel LHV/HHV basis). ✅ Indirect loss method – Very accurate for boilers > 100,000 lb/hr steam. Losses include dry flue gas, moisture from fuel/fuel H₂, moisture in air, unburned carbon, radiation/convection, and unmeasured losses. ✅ Well-tested, industry-accepted – Used for decades in performance guarantee tests. ✅ Detailed correction curves – For deviations in feedwater temperature, ambient temperature, fuel composition, etc. ✅ Fuel flexibility – Works for gas, oil, solid fuels (with appropriate sampling).