Savings calculator

Loft insulation savings calculator

Estimate rough annual savings and simple payback from topping up loft insulation, based on your heating spend, current loft insulation depth and likely installation cost.

Last reviewed: 16 April 2026 - UK-focused estimate, not an installer quote

Quick answer

Loft insulation is often one of the cleaner payback cases when the loft is easy to access and the current insulation depth is low. The strongest return usually comes from topping up a poorly insulated loft, not from squeezing a little more out of one already near modern depth.

Enter your loft insulation details

This calculator is aimed at a rough top-up estimate, not major roof work or a difficult conversion-style loft where access and labour costs are unusual.

Use your own heating spend if you can

This calculator is much more useful with your real annual heating cost than with a guessed national average, because the saving and payback both scale from that starting point.

Current home and loft setup
Worked example: under-insulated loft

A home spending about GBP 900 a year on heating with only 100mm of loft insulation could see a useful annual saving from a top-up, especially if the loft is simple to access and install.

Worked example: already well insulated

If the loft is already near 250mm to 300mm, the extra saving from adding more is usually much smaller. Comfort may still improve, but the financial payback is less compelling.

What usually changes the result

Current insulation depth, the amount already spent on heating, fuel type, and whether installation is straightforward are the main drivers.

Assumptions used

  • The calculator uses annual heating cost as the baseline rather than trying to guess your exact heat loss in kWh.
  • The saving rate is higher where current loft insulation depth is low, and lower where the loft is already close to modern top-up depth.
  • Simple payback is installation cost divided by estimated annual saving. It does not account for future tariff changes.

When it is likely to be worth it

  • Lofts with little existing insulation and straightforward access often give the best payback.
  • Homes with higher heating costs tend to see stronger savings in cash terms.
  • If installation is awkward, the comfort benefit may still matter even when payback is slower.

Is it worth it?

Use the result together with what you know about the loft, not on its own.

  • If the payback looks strong and the loft is easy to top up, this is often a sensible upgrade.
  • If the payback looks middling, draught proofing or control changes may be worth comparing first.
  • If the loft already has a good depth of insulation, extra spend may be more about comfort and marginal gains than fast payback.
How to read the payback

A short payback usually makes the decision easier. A slower payback does not automatically mean it is a bad idea, especially where the loft is clearly under-insulated or the work is easy to do.

How much can loft insulation save in the UK?

It varies. The biggest savings usually come where the loft is under-insulated and the home already spends a fair amount on heating. The calculator gives a rough cash estimate rather than a one-size-fits-all claim.

Does loft insulation always pay back quickly?

No. Payback is usually better when current insulation is sparse and the loft is easy to top up. If the loft is already well insulated or awkward to work on, payback can be slower.

Should I compare loft insulation with smaller upgrades first?

Often yes. Low-cost measures such as draught proofing and LED upgrades can be useful benchmarks, especially where budget is tight or the loft work is not straightforward.