Insulation Savings Payback
Estimate conduction savings and simple installation payback.
Your numbers
Annual energy saving
Steady degree-day estimate; excludes air leakage, cooling changes, rebound, finance and energy-price changes.
Scenario comparison
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Formula
Use E = A(Uₒ−Uₙ)D×24/(1000η). A is area in m²; Uₒ and Uₙ are old and new transmittance in W/m²·K; D is annual heating degree days in K·day; η is system efficiency. E is annual energy saving in kWh.
Estimate conduction savings and simple installation payback.
Worked example
- Envelope area (m²)
- 100
- Old U value (W/m²·K)
- 1
- New U value (W/m²·K)
- 0.5
- Annual heating degree days (K·day)
- 2000
- Heating system efficiency
- 1
- Energy price per kWh
- 0.2
- Installation cost
- 1000
- Annual energy saving
- 2,400 kWh
- Annual bill saving
- 480
- Simple payback
- 2.08333 years
Scope and limitations
Steady degree-day estimate; excludes air leakage, cooling changes, rebound, finance and energy-price changes.
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Formula version: 966099260e37 · Example checked: