Heating-degree-day cost calculator

The factor 24 converts degree days to degree hours for continuous operation.

Units

C_{h} = \frac{U \times A \times \mathrm{HDD} \times 24 \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

C_{h} = \frac{0.085 \times 4800 \times 4200 \times 24 \times 0.000015}{0.85} \approx 725.8

Symbol	Meaning	Unit
$C_{h}$	annual heating cost	$/yr
$U$	overall conductance	Btu/(h·ft²·°F)
$A$	surface area	ft²
$\mathrm{HDD}$	heating degree days at the selected base	°F·day/yr
$c_{f}$	fuel price	$/Btu
$\eta_{h}$	heating efficiency	fraction

Symbol	Meaning	Unit
$C_{h}$	annual heating cost	$/yr
$U$	overall conductance	W/(m²·K)
$A$	surface area	m²
$\mathrm{HDD}$	heating degree days at the selected base	K·day/year
$c_{f}$	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.