Which Energy Suppliers Must Fund ECO and What Each Offers

The Energy Company Obligation (ECO) started in 2013 and requires energy suppliers to fund heating and insulation improvements in homes across Great Britain¹. The suppliers that must take part are the medium and large ones: the scheme places a Home Heating Cost Reduction Obligation on medium and large energy suppliers, and under ECO4 a supplier becomes obligated once it supplies at least 150,000 customers in the relevant qualification year². The current phase, ECO4, runs to 31 March 2026, and the Government announced in Budget 2025 that funding for ECO would end in March 2026⁴. The scheme has since been extended to 31 December 2026⁶.

Between 2013 and December 2025, ECO delivered 4.4 million measures in 2.6 million homes across Great Britain⁵. Suppliers have, in aggregate, exceeded all their obligation targets up to the end of ECO3⁵.

The Energy Company Obligation explained and who funds it

ECO is a legal obligation on energy suppliers to improve the energy efficiency of domestic properties. It places legal obligations on suppliers to deliver energy efficiency measures to domestic premises, and it is designed to tackle fuel poverty and help reduce carbon emissions². The obligation is not a government grant paid from taxation: the money comes from the suppliers themselves, recovered through a charge on energy bills, which is covered in a later section.

The scheme provides funding to improve energy efficiency in difficult to treat housing and in the homes of those most in need⁹. Under ECO4, obligated suppliers are legally required to help reduce heating costs for low income and vulnerable households by delivering energy efficiency and heating measures¹⁰. The obligation falls on the suppliers, not on installers or councils: a council may refer a household through flexible eligibility, but the funding and the decision to install sit with the obligated supplier¹¹.

ECO is an energy efficiency scheme for Great Britain, so it covers England, Scotland and Wales, with ECO4 applying in all three nations⁷. Northern Ireland is outside the scheme and has its own separate programme.

Obligated suppliers and the way targets are divided up

The obligation falls on medium and large energy suppliers². Under ECO4, a supplier must supply at least 150,000 customers in the relevant qualification year to be obligated for a given phase, and each supplier that exceeds the thresholds has an obligation calculated based on each unit of supply above the supplier allowance³.

The overall target is not split evenly. It is divided between obligated suppliers according to each supplier's relative share of the domestic gas and electricity market, so the biggest suppliers carry the largest share². Under ECO3, a total of 26 suppliers were obligated under the scheme, which gives a sense of how many companies beyond the big six have carried the obligation¹³. Only obligated suppliers may take part in trades, so smaller suppliers cannot buy their way into or out of the scheme's market³.

The record of delivery is strong in aggregate: suppliers exceeded all their obligation targets up to the end of ECO3⁵. Ofgem publishes monthly reports showing how suppliers are progressing towards their targets and the number and types of measures installed, so a household can check which suppliers are actively delivering¹⁴.

Measures covered by ECO: insulation, heating and solar

ECO obliges suppliers to deliver measures such as insulation, heating, and solar panels⁶. In practice this means funding to upgrade heating or improve home insulation, and qualifying householders can access it through the scheme¹⁵. The Affordable Warmth element of earlier phases provided basic heating and insulation measures for the poorest and most vulnerable households, and that focus on low income and vulnerable households continues under ECO4¹⁶.

There are quality controls on who does the work. All ECO4 measures, except district heating connections, must be installed by, or under the responsibility of, a person registered with TrustMark or an equivalent body, and the installation must be lodged with TrustMark or equivalent¹⁷. Installers under ECO must be TrustMark accredited and will have a registration number, which a householder can ask to see¹⁸. More detail on this requirement is on our page about TrustMark registered installers under ECO4.

Scheme costs and where the money comes from

ECO is funded through a charge on the energy bills of all customers of regulated energy companies with over 250,000 customers¹⁹. In other words, the suppliers meet the cost of the measures, but they recover that cost across their customer base, so every billpayer contributes rather than the Treasury. This is the same model used for other environmental and social schemes that Ofgem administers on behalf of the UK government and the devolved administrations²⁰.

For an individual household, the position is twofold. If you receive funded measures, the supplier pays for them directly and you pay nothing beyond your normal bills, though the level of support varies by supplier because ECO is not a grant scheme with fixed amounts¹⁸. If you do not receive measures, you still pay your share of the levy through your bills. The scheme therefore transfers cost from the households that receive measures to the billpaying population as a whole.

How Ofgem administers the scheme: targets, audits and enforcement

Ofgem is the ECO administrator²¹. Its role involves setting targets for each obligated energy supplier, ensuring compliance, and monitoring suppliers' progress towards those targets¹⁸. Its work includes calculating suppliers' obligations and tracking performance against them, processing notifications, auditing suppliers, counter fraud, and reporting to the Secretary of State at the Department for Energy Security and Net Zero².

Ofgem has real teeth. It uses information gathering powers under the ECO4 Order to require suppliers to provide information about proposals, evidence of compliance and the costs of achieving their obligations³. Where a supplier fails to meet the requirements of the ECO4 Order, Ofgem may take enforcement action, which can include opening investigations, making orders and imposing penalties³. Ofgem also sends suppliers an annual sample of the measures they have notified during the year for audit, and where it identifies that local authorities have not carried out adequate due diligence checks on flexible eligibility referrals, it will include this in the report²².

Eligibility rules and applying via your supplier

The main eligibility route is benefits. You could be eligible for ECO if you receive at least one of the following: Child Benefit, Pension Guarantee Credit, Income-related Employment and Support Allowance, Income-based Jobseeker's Allowance, Income Support, Universal Credit, Housing Benefit, or Pension Credit Savings Credit¹⁸. Tax Credits, including Child Tax Credits and Working Tax Credits, also appear on the qualifying list, and income thresholds apply to Child Benefit²³. Our page on which benefits qualify for ECO4 funding covers the detail.

Applying is a matter of contacting a supplier directly. You can contact any of the obligated energy suppliers to find out how they may be able to help you benefit from the scheme, even if they are not your energy provider, and Ofgem publishes an obligated supplier contact details page for this purpose¹⁸. Eligible residents need to contact a participating energy supplier, and the list is on Ofgem's website¹¹. There is also a second route: under ECO4 Flex, local authorities can refer households that do not receive a qualifying benefit, following guidelines set by Ofgem, so a council referral is worth exploring if you are not on benefits¹¹. Questions about supplier compliance go to ecogbis_compliancequeries@ofgem.gov.uk¹⁴.

Where ECO falls short: eligibility caveats and what Ofgem does not oversee

The most important caveat is that eligibility is not an entitlement. Ofgem states it plainly:

Ofgem guidance¹⁸

It is up to energy suppliers to determine which measures they want to fund, the level of funding they provide, and the retrofit coordinator or installers they choose to work with¹⁸. ECO is not a grant scheme, and different companies or installers may provide different levels or types of support¹⁸. Two neighbours with identical homes and identical benefits can be offered entirely different outcomes depending on which supplier they approach.

Ofgem's oversight also has limits. It has no oversight of the contractual arrangements between the obligated energy companies and the installers they use, and it cannot guarantee that an energy supplier will undertake remedial works if something goes wrong with an installation²⁴. Where an issue remains after the complaints steps, and the measure is an ECO measure within the current scheme that the supplier wants to count towards its targets, Ofgem expects the supplier to have a process to assist with rectification, but that is an expectation rather than a guarantee²⁴. Complaints about an installation follow the Ofgem complaints process page¹⁴.

When the scheme closes: funding, applications and next steps

ECO4 runs until 31 March 2026¹⁵. The Government announced in Budget 2025 that funding for ECO would end in March 2026⁵. The scheme has since been extended to 31 December 2026, and energy efficiency measures under ECO will continue until the end of 2026⁶. The Government also consulted on extending the ECO4 end date, which set out that the scheme obligates the larger energy suppliers to deliver a target of annual bill savings by installing energy efficiency and heating measures in homes²⁵.

For households with projects in flight, the position is reasonably clear. There is no limit on the number of applications a supplier can make on or before 31 March 2027, so measures notified before the deadlines can still be processed and counted towards supplier targets³. A household that has already been assessed or has an installation scheduled should stay in contact with its supplier, but the formal machinery for completing projects continues beyond the end date for new work.

ECO's impact on household energy self sufficiency

ECO is one of the few routes by which a household can get substantial energy work done at no direct cost, and the measures it funds, insulation, heating and solar panels, are exactly the ones that cut a home's dependence on bought energy. A better insulated home with a modern heating system uses less gas or electricity whatever the price does, and solar panels funded through the scheme reduce the amount a household must buy from a supplier at all. Over 4.4 million measures have been delivered on this basis since 2013⁵.

The dependence that remains is real, though. The household does not choose the measure, the installer or the funding level: the supplier does¹⁸. The scheme itself is paid for through a levy on everyone's bills, so even a household that receives nothing still contributes¹⁹. And the scheme is closing: funding ends in March 2026 with delivery extended to 31 December 2026, so the window for a household to benefit is finite⁵. For a household weighing ECO against other routes, our pages on the Boiler Upgrade Scheme and the Great British Insulation Scheme set out the alternatives, and the full picture is in our guide to home energy grants and schemes in the UK.