Annual setback fuel-cost savings calculator

Use weather-bin calculations or the nomograph for useful heat savings, then adjust for efficiency.

Units

S = \frac{q_{\text{saved}} \times A \times c_{f}}{\eta_{h}}

Calculator

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

Given

S = \frac{4800 \times 18{,}000 \times 0.000012}{0.8} = 1{,}296

Symbol	Meaning	Unit
$S$	annual cost savings	$/yr
$q_{\text{saved}}$	useful heat saved per area	kWh/(m²·year)
$A$	heated area	m²
$c_{f}$	fuel-energy price per kilowatt-hour	$/kWh
$\eta_{h}$	heating efficiency	fraction

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