Annual fuel energy avoided by efficiency improvement calculator

Annual avoided fuel energy is calculated as Q_useful × (1/η_old − 1/η_new). Use the stated system boundary and matching input units.

Units

\Delta F = Q_{\text{useful}} \times \left(\frac{1}{\eta_{\text{old}}} - \frac{1}{\eta_{\text{new}}}\right)

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Given

\Delta F = 20{,}000 \times \left(\frac{1}{0.75} - \frac{1}{0.85}\right) \approx 3{,}137

Symbol	Meaning	Unit
$\Delta F$	annual avoided fuel energy	MMBtu/year
$Q_{\text{useful}}$	unchanged annual useful heat	MMBtu/year
$\eta_{\text{old}}$	initial boiler efficiency	—
$\eta_{\text{new}}$	improved boiler efficiency	—

Symbol	Meaning	Unit
$\Delta F$	annual avoided fuel energy	GJ/year
$Q_{\text{useful}}$	unchanged annual useful heat	GJ/year
$\eta_{\text{old}}$	initial boiler efficiency	—
$\eta_{\text{new}}$	improved boiler efficiency	—

Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.