Estimate wall-insulation payback
| Annual wall heat loss before | 10,368 kWh |
| Annual wall heat loss after | 1,728 kWh |
| Estimated annual saving | 8,640 kWh · $1,037 |
| Simple payback | 4.8 years |
Important: this is a wall-conduction estimate only. It excludes windows, roofs, floors, air leakage, thermal bridges and cooling effects; use it for early planning, not a final building specification.
What this estimate includes
The calculation models conductive heat loss through one wall area before and after insulation. It converts the estimated kWh reduction into a cost saving using the energy price you enter.
Use this for early planning
A whole-building assessment should include the roof, floor, windows, ventilation and local building requirements. Ask a qualified professional to specify a retrofit.
How U-values turn into kilowatt-hours
Heat loss through a wall is U-value × area × temperature difference. Over a heating season this is usually estimated with heating degree-days (HDD): annual kWh ≈ U × A × HDD × 24 / 1000. For 50 m² of wall in a climate with 2,500 degree-days:
| Wall | U-value (W/m²K) | Annual heat loss |
|---|---|---|
| Uninsulated solid wall | 1.5 | 4,500 kWh |
| After insulation | 0.3 | 900 kWh |
| Saving | 3,600 kWh |
The money saved is that heat divided by the heating system's efficiency, multiplied by the fuel price. Degree-days for your location are published by national weather services; the U-values above are typical illustrations, not measurements of a particular wall.