Fuel Energy Saved (Boiler Efficiency Adjustment)

Converts recovered or lost useful heat into the larger amount of fuel energy actually displaced or consumed, accounting for boiler efficiency. At 80% efficiency, 1.25 BTU of fuel is burned per BTU of useful heat delivered.

$$\text{Fuel energy saved}=\frac{\text{Heat recovered}}{\text{Boiler Efficiency}}$$

Variables

Symbol	Meaning	Unit
Heat recovered	Useful heat recovered or lost	MMBTU/yr or BTU/hr
Boiler Efficiency	Fraction of fuel energy delivered as useful heat	dimensionless

Worked example

5,475 MMBTU/yr of recovered condensate heat at 80% efficiency displaces 5,475 / 0.8 = 6,844 MMBTU of fuel per year.

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Part of The Blueprint of Water