Building Heat Loss Calculator
Fill in the values and the answer updates as you type.
How the Building Heat Loss Calculator 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.
Inputs and results
The Building Heat Loss Calculator takes 7 inputs and gives 3 results.
What you enter
- U-value (W/m²K) — starts at 0.35.
- Surface area (m²) — starts at 120.
- Indoor temperature (°C) — starts at 21.
- Outdoor temperature (°C) — starts at 0.
- Heating hours per day (h) — starts at 12.
- Energy price ($/kWh) — starts at 0.15.
- Heating system efficiency (%) — starts at 95.
What you get
- Heat loss (W)
- Energy per day (kWh)
- Monthly heating cost (30 days)
Example: Building Heat Loss Calculator with the starting values
With u-value 0.35 W/m²K, surface area 120 m², indoor temperature 21 °C, outdoor temperature 0 °C and heating hours per day 12 h, the calculator returns:
| Heat loss (W) | 882 |
|---|---|
| Energy per day (kWh) | 10.6 |
| Monthly heating cost (30 days) | $50.13 |
Change any value above and the results update straight away.
Building Heat Loss Calculator FAQ
How do I use the Building Heat Loss Calculator?
Enter u-value, surface area, indoor temperature and outdoor temperature in the fields, then read heat loss (w), energy per day (kwh) and monthly heating cost (30 days) in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Building Heat Loss Calculator calculate?
Heat loss through walls, windows, or a roof, and the heating cost. It returns heat loss (w), energy per day (kwh) and monthly heating cost (30 days) from the 7 values you provide.
What values does the Building Heat Loss Calculator start with?
It opens with u-value 0.35 W/m²K, surface area 120 m², indoor temperature 21 °C and outdoor temperature 0 °C so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Building Heat Loss Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Building Heat Loss Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.