Quick answer: Loft insulation plus cavity wall insulation, the typical insulation job, costs a modelled UK average of £2,950 (Energy Saving Trust installed prices, September 2026), with a range of £1,918 to £4,573. At up to £478 a year in estimated savings for a semi that has neither, its modelled payback of around 6 years is second only to EV chargers in our index.
Pound for pound, few other upgrades we model come close. This page sets out the insulation numbers from our UK Home Energy Cost Index; for choosing between loft, cavity and solid-wall measures, see the insulation guide — and the U-value glossary entry explains the key performance measure.
Key insulation statistics for 2026
- Loft and cavity wall insulation together cost a modelled UK average of £2,950 — Home Energy Quotes Cost Index, September 2026 (Energy Saving Trust installed prices).
- Most loft-and-cavity jobs fall between £1,918 and £4,573 depending on property size — Home Energy Quotes Cost Index, September 2026 (modelled).
- Insulation is the fourth-cheapest upgrade in our index — a little under half the cost of solar — Home Energy Quotes Cost Index, September 2026 (modelled).
- London loft-and-cavity jobs average a modelled £3,540; Northern Ireland £2,100, where the Energy Saving Trust prices cavity wall insulation at about £1,000 — Home Energy Quotes Cost Index, September 2026 (modelled).
- The most-to-least expensive regional gap is £1,440 — Home Energy Quotes Cost Index, September 2026 (modelled).
- North West and Yorkshire households both average £2,803, 5% below the national figure — Home Energy Quotes Cost Index, September 2026 (modelled).
- Loft and cavity wall insulation could save a semi that has neither up to £478 a year, while a loft top-up from 120mm saves about £21 (estimate, Energy Saving Trust figures re-priced) — Home Energy Quotes Cost Index, October–December 2026 price cap (modelled).
- Modelled simple payback is around 6 years, second only to EV chargers among the upgrades we track — Home Energy Quotes Cost Index, October–December 2026 price cap (modelled).
- Insulation’s modelled annual saving (£478) is higher than a heat pump’s (£272) on the October–December 2026 cap, for about a quarter of the pre-grant cost — Home Energy Quotes Cost Index (modelled).
- Insulation carries 0% VAT until March 2027 — GOV.UK, checked July 2026.
- The Warm Homes: Local Grant offers up to £16,600 for insulation (within a £33,200 per-home cap) for eligible households, open to March 2028 — GOV.UK, checked July 2026.
- With gas at 7.97p/kWh under the October–December 2026 Ofgem price cap, every kWh of heat your insulation keeps in is money not spent.
Insulation costs by UK region
Insulation is labour-heavy work, so regional wage differences show up clearly. These figures are for loft plus cavity wall insulation: a loft top-up alone costs far less, and solid-wall insulation far more, about £12,000 to £15,000 (Energy Saving Trust). Northern Ireland sits lower because the Trust prices cavity wall insulation there at about £1,000, against £2,200 in Great Britain.
| Region | Modelled cost, loft and cavity wall insulation | vs UK average |
|---|---|---|
| UK average | £2,950 | — |
| London | £3,540 | +20% |
| South East | £3,304 | +12% |
| East of England | £3,127 | +6% |
| South West | £3,098 | +5% |
| West Midlands | £2,891 | −2% |
| East Midlands | £2,862 | −3% |
| Scotland | £2,832 | −4% |
| Yorkshire & the Humber | £2,803 | −5% |
| North West | £2,803 | −5% |
| Wales | £2,773 | −6% |
| North East | £2,744 | −7% |
| Northern Ireland | £2,100 | −29% |
All modelled figures on this page come from the Home Energy Quotes Cost Index — insulation prices start from the Energy Saving Trust’s installed costs (checked September 2026), adjusted by our regional labour indices, with Northern Ireland on the Trust’s own Northern Ireland prices. They are not quotes for your specific home. Real insulation prices vary with property type, spec and installer, so treat these as a starting point and read how we calculate costs for the full method and its limitations.
Grants and VAT relief
Insulation is one of the best-supported upgrades. The Warm Homes: Local Grant can fund insulation worth up to £16,600 for households in EPC D–G homes with income under £36,000 — free, and open to March 2028. All insulation also carries 0% VAT until March 2027. The Great British Insulation Scheme, however, closed on 31 March 2026, so check the current grant list before assuming an older guide still applies.
Use the savings calculator to see what insulation could knock off your own heating bill at today’s cap rates.
Download the dataset
The full Cost Index (9 upgrades × 12 UK regions: installed costs July 2026, savings at the October to December 2026 price cap) as CSV: gre-cost-index.csv. Free to reuse with attribution (CC BY 4.0) — please credit Home Energy Quotes and link the methodology. Figures are modelled estimates, not quotes.