Insulation / draught-proofing payback
Stack loft, cavity, draught-proofing and glazing measures with multiplicative heat-loss reductions.
Your situation
Measures (applied in order, multiplicatively)
Incl.?
Yes — in package
Incl.?
Yes — in package
Incl.?
Yes — in package
Incl.?
Skipped
Estimate only. Based on the assumptions you entered. Get a site-specific survey before spending money.
Combined annual saving
€468
Package cost
€2,250
Package payback
4.8 years
Heating cost after measures
€1,032
Per-measure (in order)
- Loft insulation (−15%)save €225/yr · payback 3.6 yr
- Cavity wall insulation (−12%)save €153/yr · payback 7.8 yr
- Draught-proofing (−8%)save €89.76/yr · payback 2.8 yr
Formula with your numbers
remaining starts at €1,500
after Loft insulation: remaining × (1 − 15/100); saving €225; payback 800 / saving
after Cavity wall insulation: remaining × (1 − 12/100); saving €153; payback 1200 / saving
after Draught-proofing: remaining × (1 − 8/100); saving €89.76; payback 250 / saving
package_payback = €2,250 / €468
Frequently asked questions
Why multiplicative reductions?+
You cannot save the same heat twice. If loft insulation cuts remaining heat loss by 15% and draught-proofing by 10%, remaining demand is 0.85 × 0.90 of the start — not 25% off additively.
Related tools
Tariff compare
Split usage across peak, off-peak and night bands and rank up to three tariffs.
kWh converter
Convert freely between kilowatt-hours, cost and CO₂ using editable grid intensity.
Solar payback
Estimate simple payback and 25-year net gain from a rooftop PV system with transparent assumptions.