Heat loss, heating energy and cost
Window Heat Loss Calculator
Estimate steady window heat loss, monthly heating energy and cost from area, U-factor and temperature difference.
Imperial and metric Rounded purchase quantities Cost estimate
Default project preview
2,800 BTU/h
Thermal loss
0.82 kW
Monthly delivered heat
295.4 kWh
Monthly input energy
328.2 kWh
Monthly heating cost
$59.08
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Advertisement
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Heat loss = area × U-factor × temperature difference. Input energy divides by heating efficiency or COP.
FAQ
Window Heat Loss Calculator questions
Does a lower U-factor reduce heat loss?+
Yes. Lower U-factor means less heat transfer.
Are drafts included?+
No. Air leakage is separate.
Can a heat-pump COP be entered?+
Yes. Enter a representative operating value.