Building Heat Loss Calculator
Heat loss through walls, windows, or a roof, and the heating cost.
W/m²K
m²
°C
°C
h
$/kWh
%
How it works
Heat loss (W) = U-value × area × temperature difference. A lower U-value means better insulation. Daily energy = loss × heating hours ÷ 1000, and the cost divides by system efficiency. Add up several surfaces by running the calculation for each. The estimate assumes a constant temperature difference. Example: with the default values, heat loss comes to 882 W.
FAQ
Is this calculator free?
Yes. No signup is needed and nothing you enter is stored.
Is the result exact?
Results are rounded for display. For financial, medical, or legal decisions, confirm with a professional.
Do my numbers leave my device?
No. The calculation runs in your browser.