ECO4 Window Grant Eligibility: Income, EPC and Measure Criteria

ECO4 runs until 31 December 2026 and has allocated over £4 billion of energy company obligation funding — but the scheme’s rules on which homes qualify for window replacements catch out more applicants than any other single measure.

The three eligibility gates

ECO4 is not a single test. You must pass through three gates, and failing any one means your application stops.

Gate 1: The property’s EPC rating

ECO4 targets the least efficient homes. Your property must have an EPC rating of D, E, F, or G. If your home is rated C or above, you do not qualify for any ECO4 measure — including windows.

This is the gate that catches the most people. A mid-terrace Victorian house with original sash windows may feel cold and cost a fortune to heat, but if the EPC assessor gave it a low-C band (which is common where the walls have cavity insulation and the loft is insulated), ECO4 is closed.

Check before you apply: Search your property’s EPC at the government register (find-energy-certificate.service.gov.uk). Certificates last 10 years. If yours is older than 10 years, you may need a new assessment.

Gate 2: The resident’s eligibility

ECO4 has two resident routes:

Route	Criteria	Notes
Main route	Receiving a qualifying benefit	Listed below
Local Authority route	Nominated by a LA as fuel-poor or low-income	LA refers you — you do not apply directly

Qualifying benefits for the main route:

• Pension Credit (Guarantee Credit or Savings Credit)
• Income-related Employment and Support Allowance (ESA)
• Income-based Jobseeker’s Allowance (JSA)
• Income Support
• Universal Credit (with household income below a threshold)
• Child Tax Credit (with household income below £16,190)
• Working Tax Credit (with household income below £16,190)
• Carer’s Allowance (added under ECO4)
• Disability Living Allowance (DLA)
• Personal Independence Payment (PIP)
• Attendance Allowance
• Armed Forces Independence Payment
• Constant Attendance Allowance
• War Pensions Mobility Supplement
• Industrial Injuries Disablement Benefit

If you are on Carer’s Allowance but no other benefit, you qualify under ECO4’s expanded criteria. Previous ECO phases did not include carers — this is a change that many advice pages have not yet updated.

Gate 3: The measure rules

Even if your home is EPC D-G and you receive a qualifying benefit, ECO4 does not automatically pay for new windows. The measure rules dictate what can be installed and when.

ECO4 measure rules for windows

ECO4 operates a “whole-house” approach. Measures are not chosen individually — they are selected as a package that improves the property’s EPC to at least band C (or as close to C as practical). Windows are a secondary measure, meaning they can only be funded as part of a package that includes a primary measure.

Primary measures (must be installed first or alongside)

• Insulation (cavity wall, loft, solid wall, floor)
• Heating system upgrade (boiler replacement, first-time central heating, heat pump)

Secondary measures (funded only alongside a primary measure)

• Windows (double glazing where single exists, or upgrading existing double to A-rated)
• Doors (if they contribute to the thermal improvement of the property)
• Draught-proofing
• Hot water cylinder insulation

The practical implication

You cannot apply for ECO4 windows alone. If you need new windows but your loft and walls are already insulated and your boiler is recent, ECO4 will not fund the windows because there is no primary measure to pair them with.

This is the most common reason for ECO4 window applications being rejected: the home already has adequate insulation, so there is no package to build.

The EPC uplift requirement

ECO4 requires that the package of measures lifts the property by at least one EPC band. The assessor calculates this before the work starts, using the Standard Assessment Procedure (SAP). If replacing single glazing with A-rated double glazing does not move the EPC from, say, E to D, then windows will not be included in the package — the funding will go to insulation or heating instead.

How much do windows contribute to an EPC uplift?

Windows affect the “thermal fabric” element of the EPC. The exact uplift depends on the starting point:

Starting glazing	Upgraded to	Typical EPC points gain
Single glazing	A-rated double	8-15 SAP points
Old double (1990s)	A-rated double	3-8 SAP points
Double (post-2002)	A-rated double	1-4 SAP points

A single-to-double upgrade on a typical 3-bed semi can shift the EPC by a whole band. An old-double-to-new-double upgrade rarely shifts it by more than a few points.

For more detail on how glazing affects EPC, see our EPC uplift and glazing guide and the broader energy performance certificate explanation.

Can you get windows under GBIS or HUG2?

ECO4 is not the only grant scheme. Two others operate alongside it:

Great British Insulation Scheme (GBIS)

GBIS is a single-measure scheme focused on insulation. Windows are not an eligible measure under GBIS. If you want grant-funded windows, GBIS will not provide them.

However, GBIS and ECO4 can be stacked. A homeowner could receive loft insulation under GBIS and then use that insulation as the primary measure to enable ECO4-funded windows. This stacking approach requires an installer who manages both schemes — ask specifically when you enquire.

Home Upgrade Grant Phase 2 (HUG2)

HUG2 is a local authority-led scheme for off-gas-grid homes. Windows are an eligible measure under HUG2 if the property has an EPC of D-G and is not connected to the mains gas network. HUG2 funds are allocated by local authority — check with your council whether HUG2 funding remains available in your area.

Grant stacking: combining schemes

Combination	Windows funded?	Condition
ECO4 alone	Yes	Property EPC D-G + qualifying benefit + primary measure
ECO4 + GBIS	Yes	GBIS funds insulation (primary measure), ECO4 funds windows
ECO4 + HUG2	Yes	HUG2 fills gaps in the ECO4 package
GBIS alone	No	Windows are not a GBIS measure

The TrustMark requirement

All ECO4 installations must be carried out by a TrustMark-registered installer. TrustMark is the government-endorsed quality scheme for home improvements. An installer who is not TrustMark-registered cannot access ECO4 funding, regardless of their competence.

This matters because many established window installers are FENSA-registered but not TrustMark-registered. If your preferred installer is FENSA-only, they cannot deliver ECO4-funded windows. You will need to find a TrustMark-registered installer or ask your current installer to register.

What to expect from an ECO4 window installation

If you qualify, the process runs as follows:

1. Referral or application: Through an energy supplier, a local authority, or a TrustMark installer
2. Technical survey: A qualified assessor visits the property, measures the windows, and calculates the EPC uplift
3. Package design: The installer designs a package of measures (primary + secondary) that achieves the required EPC uplift
4. Installation: Typically 4-8 weeks from approval; windows are manufactured to measure
5. Post-installation EPC: A new EPC assessment confirms the uplift has been achieved
6. No cost to the householder: ECO4 covers the full cost of the materials and installation — you do not pay

Common reasons for rejection

1. EPC band C or above: The most common reason. Your home is too efficient already.
2. No qualifying benefit: You do not receive any of the listed benefits.
3. No primary measure available: Your home already has adequate insulation and a modern boiler — windows alone are not enough.
4. Listed building or conservation area: Window replacement may be restricted by planning controls. ECO4 will not fund a measure that requires planning permission that has not been granted.
5. Already received ECO measures: If your home had ECO3-funded work that should have resolved the glazing, ECO4 may not fund a second upgrade.

Summary

• ECO4 can fund window replacements, but only as part of a package that includes a primary measure (insulation or heating)
• Your property must be EPC rated D-G and you must receive a qualifying benefit
• Windows alone are not funded — you need insulation or a heating upgrade first
• GBIS does not fund windows, but can provide the primary measure that activates ECO4 window funding
• A TrustMark-registered installer is mandatory — your local FENSA fitter may not qualify