Great British Insulation Scheme and Solar: What's Covered?

GBIS was launched in April 2023 as part of the government's energy efficiency programme. It sits alongside ECO4 but with broader eligibility — designed to help a wider range of households access a single insulation measure.

GBIS is targeted at properties that would benefit most from insulation — homes rated EPC D or below — and makes funding available to both low-income households on benefits and a broader group of lower-income households even without qualifying benefits.

GBIS funds a single primary insulation measure per property. The most commonly installed measures are:

• Loft insulation — the most cost-effective home energy improvement in the UK — saves £175–£300/year for a typical semi
• Cavity wall insulation — for properties with unfilled cavity walls — saves £145–£170/year
• Solid wall insulation (internal) — for pre-1920s solid-brick properties
• Underfloor insulation — where accessible floor void exists
• Room-in-roof insulation — for properties with converted lofts

GBIS has a two-group eligibility structure, making it more broadly accessible than ECO4:

Group A — means-tested (benefits-based)

Households receiving qualifying benefits (same list as ECO4), in any property regardless of EPC rating.

Group B — broader eligibility

Households in EPC band D or below, in council tax bands A–D, without needing to be on qualifying benefits. This is the significant expansion — homeowners with modest incomes who aren't on benefits but live in relatively poorly-insulated homes can qualify.

GBIS matters for solar buyers for a reason that's easy to overlook: insulation should come before solar.

A solar system is sized to cover a portion of your electricity demand. If you insulate after installing solar, your heating demand falls and your home retains heat better. The solar system you installed may now be slightly oversized for the reduced load — which isn't a disaster, but means you could have installed a smaller, cheaper system.

Conversely, insulating before solar means the solar system is sized to your post-insulation demand — the right size, delivering optimal economics from day one.

For a homeowner with an EPC of D or E:

• Step 1: Check GBIS eligibility — if qualified, access free loft or cavity wall insulation.
• Step 2: Re-assess electricity demand post-insulation (particularly if you have electric heating).
• Step 3: Size and install solar system based on post-insulation demand — likely 1–2 panels fewer than pre-insulation sizing.
• Step 4: EPC improves with both insulation and solar — potentially moving from D to B or C, with significant mortgage, resale and rental compliance benefits.

For lower-income households qualifying for both GBIS (insulation) and Warm Homes Plan (solar), the two can be coordinated as a single whole-house improvement package — potentially covering insulation, solar and battery storage at no cost.

GBIS is delivered through energy suppliers and approved installers. The process:

• Contact an approved installer (like Alliant) or your energy supplier's grant team
• Eligibility is checked — EPC rating, council tax band, income/benefits status
• If eligible, a free survey confirms which measure is most appropriate
• The measure is installed at no cost if fully funded, or with a potential contribution for some Group B measures

Alliant is approved for energy efficiency installations under GBIS. We check eligibility and manage the process — including coordinating GBIS insulation with any subsequent solar installation.