See how much you could save every year with loft insulation, cavity wall insulation, internal wall insulation (IWI) or external wall insulation (EWI). Based on Energy Saving Trust figures for a typical gas-heated UK home.
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EcoHome UK installs every measure shown above. Most homeowners qualify for grant funding under ECO4 or GBIS — we'll check for free.
Get a free survey →How is this calculated? (Methodology & sources)
Annual savings figures are based on data published by the Energy Saving Trust for typical gas-heated homes in Great Britain. Figures assume the Ofgem default tariff cap. Real savings vary depending on house age, occupancy, current energy prices and the specific install.
Annual savings used (£/year, fully uninsulated baseline):
| House type | Loft insulation | Cavity wall | Solid wall (IWI/EWI) |
|---|---|---|---|
| Detached | £590 | £515 | £590 |
| Semi-detached | £355 | £325 | £375 |
| Mid-terrace | £305 | £215 | £240 |
| End-terrace | £330 | £270 | £310 |
| Detached bungalow | £410 | £305 | £350 |
| Mid-floor flat | £255 | £160 | £200 |
Adjustments applied:
- If you already have some loft insulation (under 120mm), loft top-up saving = 25% of the figure above.
- If walls are already insulated, that measure is excluded.
- IWI (internal wall insulation) and EWI (external wall insulation) deliver near-identical thermal savings; we show the same figure with notes on the practical differences.
- Cavity wall insulation only applies to homes with cavity walls. Solid wall insulation only applies to homes with solid walls.
- CO₂ figures use BEIS standard conversion factors: 0.183 kg CO₂ per kWh of gas displaced.
- Lifetime saving uses 25 years (typical PAS 2030/2035 lifespan) and assumes flat real energy prices — likely a conservative estimate.
Sources: Energy Saving Trust — Home Insulation, Ofgem energy price cap, UK Government GHG conversion factors.
This calculator is for guidance only. For an accurate quote based on your specific property, request a free survey.
What's the difference between IWI and EWI?
Internal Wall Insulation (IWI) is fitted to the inside face of external walls. Cheaper than EWI but reduces internal floor area slightly and is disruptive to fit (requires moving sockets, skirting, redecorating).
External Wall Insulation (EWI) is fitted to the outside of the building and rendered over. More expensive, but no internal disruption, and it dramatically improves the look of older properties. Often the best choice for solid wall homes that need re-rendering anyway.
Both deliver similar energy savings — the choice usually comes down to budget, planning constraints, and what you want the house to look like. EcoHome UK installs both.