Payback Period Calculator
The honest question: how many years until new windows pay for themselves? Plug in your install quote, your annual heating savings, and any grant funding. We'll tell you the break-even year — and whether it's worth doing at all.
Break-even year — —
- Net install cost (after grant)
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- Total savings over lifetime
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- Net lifetime gain / loss
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- Effective annual return
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Break-even year assumes annual savings grow with the energy-inflation input, discounted at the discount-rate input. Effective annual return is the internal rate of return (IRR) across the window's expected lifetime — the "interest rate" your install effectively earns.
How to read the verdict
- Break-even < 8 years: very strong. Most homeowners keep their house longer than that, so you'll capture the gain.
- 8–15 years: solid. Worth doing if you're staying put, if the windows are visibly failing, or if comfort / noise reduction is a driver in its own right.
- 15–25 years: marginal on energy alone. Only do it if the old windows are rotten, leaking, or the house sale needs them replaced.
- > 25 years: bad deal on pure economics. Reconsider — maybe secondary glazing or draught-proofing is the cheaper fix. See our secondary glazing guide.
Next step
Grant Eligibility Checker — ECO4 / HUG2 grants can slash
your net install cost, improving payback dramatically.
Cost Calculator — get a real install-cost estimate for your postcode.