The single most important fact cavity wall insulation grants cover most of the cost for most homeowners in 2026
If you own a home with unfilled cavity walls, you may be wondering whether the government still offers financial help to insulate them. The answer is yes, and the support is more generous than many realise.
The Great British Insulation Scheme (GBIS) and the Energy Company Obligation (ECO4) are the two main government-backed routes for free or heavily subsidised cavity wall insulation in 2026. Eligibility is primarily based on household income, receipt of certain benefits, or the property’s Energy Performance Certificate (EPC) rating. A full cavity wall insulation installation typically costs £1,500–£2,500, but grants can reduce the homeowner’s share to £0 in many cases (GOV.UK, 2026). The scheme is administered by energy suppliers, not the government directly, so the process involves contacting your supplier or a registered installer.
The difference between the Great British Insulation Scheme and ECO4 for cavity wall grants
GBIS is a broader scheme targeting homes with the lowest EPC ratings (D–G) and does not require the household to be on a specific benefit; it focuses on a single insulation measure per property (GOV.UK, 2026). ECO4 is a more targeted scheme for low-income and vulnerable households, requiring the homeowner or a member of their household to be in receipt of a qualifying benefit such as Pension Credit, Income Support, or Child Tax Credit (Ofgem, 2026).
Both schemes are funded by a levy on energy suppliers and are legally required to meet annual installation targets set by Ofgem. The key practical difference is that ECO4 can fund multiple measures in one home (e.g., cavity wall insulation plus loft insulation), whereas GBIS typically funds one measure per property. If you are on a low income, ECO4 is the better route because it can cover a broader package of improvements. If you are not on benefits but your home is poorly insulated, GBIS is the primary option.
Quick numbers typical cost, grant value, and energy savings for cavity wall insulation in 2026
| Metric | Value |
|---|---|
| Average installation cost (unsubsidised) | £1,800 |
| Average grant value (GBIS/ECO4) | £1,800 (full cost covered if eligible) |
| Typical annual energy bill saving | £300–£400 |
| Typical payback period (unsubsidised) | 4–6 years |
| Estimated carbon saving per year | 650–750 kg CO₂ |
Figures based on a semi-detached property. The unsubsidised cost of £1,800 comes from the Energy Saving Trust’s cavity wall insulation cost guide (Energy Saving Trust, 2026). The annual saving of £300–£400 is calculated using 2026 average energy prices (Energy Saving Trust, 2026). The carbon saving of 650–750 kg CO₂ per year is based on DESNZ conversion factors (DESNZ, 2026).
How to check if you are eligible for a cavity wall insulation grant in 2026
The primary eligibility criteria for ECO4 is that your household receives one of the qualifying benefits, such as Income Support, Jobseeker’s Allowance, Pension Credit, or Universal Credit, and your property has an EPC rating of D or below (Ofgem, 2026). For GBIS, you do not need to be on a benefit, but your property must have an EPC rating of D–G and you must be a domestic electricity or gas customer (GOV.UK, 2026).
Your property must have unfilled cavity walls. Cavity walls are typical in homes built after 1920 and before the 1990s. The property must also be suitable for installation, meaning no severe damp, structural issues, or existing insulation that would need removal. If you are unsure, a free survey by an approved installer will determine suitability. You can check your EPC rating online via the government’s EPC register (GOV.UK, 2026).
The step-by-step process to apply for a cavity wall insulation grant
Step 1: Check your eligibility online using the government’s “Simple Energy Advice” tool or your energy supplier’s eligibility checker (GOV.UK, 2026).
Step 2: If eligible, contact a registered installer who is MCS-certified and approved to work under the GBIS or ECO4 scheme (MCS, 2026).
Step 3: The installer will arrange a free survey to confirm your cavity walls are suitable and measure the property for the required amount of insulation.
Step 4: If approved, the installer will schedule the work. For a typical semi-detached home, installation takes one day.
Step 5: The grant is paid directly to the installer by the energy supplier. You pay nothing if fully eligible, or a contribution if partially eligible. You should not be asked to pay the installer directly for the work covered by the grant.
How to verify your installer is certified and the work is guaranteed
All cavity wall insulation work under government schemes must be carried out by an installer registered with the Microgeneration Certification Scheme (MCS) or a similar approved body. The installer must also be registered with the Cavity Wall Insulation Guarantee Agency (CIGA) to provide a 25-year guarantee on the work (CIGA, 2026).
You can check the MCS installer database at mcscertified.com or the CIGA register at ciga.co.uk before hiring. If the installer is not MCS or CIGA registered, the work will not qualify for the grant and the guarantee may be invalid. It is also worth checking that the installer holds a valid Gas Safe Register certificate if the work involves any gas connections (Gas Safe Register, 2026). How to find a certified insulation installer
What the grant covers and what it does not cover for cavity wall insulation
The grant covers the full cost of the insulation material, such as foam or beads, and the labour for installation in eligible cavity walls. It also covers the cost of drilling the required holes and sealing them after installation (Ofgem, 2026).
The grant does NOT cover any preparatory repairs, such as fixing damp, repointing brickwork, or clearing existing insulation from a previously filled cavity. It also does NOT cover insulation in solid walls, which require a different grant route under the same schemes, or in walls with severe structural issues. If your home requires additional work to make it suitable, such as installing a damp-proof course, that cost is your responsibility and is not covered by the grant (GOV.UK, 2026).
For homeowners considering cavity wall insulation without a grant, the payback period of 4–6 years makes it a cost-effective improvement even without subsidy. However, with grants covering the full cost for most eligible households, there is little reason to delay checking eligibility. Solid wall insulation grants compared
Frequently Asked Questions
Yes, if you own a home with unfilled cavity walls and meet income or EPC criteria. Eligibility is primarily based on household income, benefits, or an EPC rating of D–G, as set by GOV.UK and Ofgem.
After a grant, your share can be £0 if you qualify fully. Without a grant, installation costs £1,500–£2,500 according to the Energy Saving Trust.
ECO4 funds multiple insulation measures for low-income households on benefits, while GBIS funds a single measure for homes with EPC D–G without requiring benefits. Ofgem sets the rules for both.
Contact your energy supplier or a registered installer directly, as grants are administered by suppliers. Check eligibility on GOV.UK before applying.
Yes, through the Great British Insulation Scheme if your home has an EPC rating of D–G. This does not require benefits, as confirmed by GOV.UK.
