Heat Loss Through a Wall Calculator
Heat lost through a surface, the daily energy it costs and the price of that energy.
Results
Heat loss
283.5
W
Energy
6.804
kWh/d
Cost
1.22
Cost
36.74
What this tool does
This is the steady-state loss through one surface: multiply the U-value by the area and by the temperature difference. It is the calculation that shows why insulating a cold wall pays for itself, and it covers conduction only — draughts and ventilation are separate losses.
Formula
Q = U × A × ΔT
Variables
| Symbol | Meaning | Unit |
|---|---|---|
u | U-value | W/(m²·K) |
a | Area | m² |
ti | Initial temperature | °C |
te | Final temperature | °C |
p | Price per kWh | — |
Q | Heat loss | W |
E | Energy | kWh/d |
C | Cost | — |
CM | Cost | — |
Worked example
- U-value0.35 W/(m²·K)
- Area45 m²
- Initial temperature20 °C
- Final temperature2 °C
- Price per kWh0.18
- Heat loss283.5 W
- Energy6.804 kWh/d
- Cost1.22
- Cost36.74
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.