To become an ECO4 provider you must be a registered energy supplier or an authorised installer working through a TrustMark-registered scheme. Ofgem reports that over 20 suppliers and 500 installer organisations are currently active in the ECO4 scheme (Ofgem, 2026).
ECO4 is the fourth phase of the Energy Company Obligation, requiring large energy suppliers to fund energy-efficiency improvements in low-income, low-energy-performance homes. You cannot apply directly to the government to become an ECO4 provider. Instead, you must partner with a licensed energy supplier or join a government-authorised certification body. The route depends on whether you are an installer or a supplier.
Apply as an energy supplier
Only energy suppliers with at least 250,000 domestic customer accounts are obligated under ECO4. Ofgem sets the annual carbon-saving targets for each supplier (Ofgem, 2026). If your supplier is below this threshold, you are not obligated but can still deliver measures voluntarily. To become a delivery partner, contact the supplier directly and agree a contract. You must hold Public Liability Insurance of at least £2 million and be registered with the Gas Safe Register for any gas work (Gas Safe Register, 2026).
Register as an approved installer
Installers must be certified by a PAS 2030:2019 accredited body, such as the Microgeneration Certification Scheme (MCS) for heating measures or TrustMark for wider retrofit work. MCS states that over 3,000 installers are currently certified for ECO4-eligible measures (MCS, 2026). You also need to complete the PAS 2035 retrofit qualification, which covers whole-house assessment and installation standards. TrustMark registration is mandatory for all ECO4 installers, and you must pass a financial viability check.
Partner with a scheme manager
Many suppliers outsource delivery to scheme managers who handle customer eligibility, quality assurance, and funding claims. To become a scheme manager, you must be TrustMark-registered and hold PAS 2030 certification for all measures you manage. The Energy Saving Trust notes that scheme managers typically charge a management fee of 10–15% of the total measure cost (Energy Saving Trust, 2026). You must also comply with Ofgem’s ECO4 scoring framework, which assigns a notional cost per tonne of carbon saved. Without a scheme manager agreement, installers cannot access supplier funding directly.
A worked example
A small insulation firm in Leeds wanting to deliver cavity wall insulation under ECO4 would need to spend roughly £8,500 upfront to get certified and registered. This typical UK business, operating from a 1970s semi-detached warehouse unit, must first gain PAS 2030:2019 certification through a TrustMark-approved body like BRE or MCS, costing around £3,500 for the initial audit and documentation. Adding Public Liability Insurance of £2 million adds £1,000 annually, while Gas Safe Register membership for any boiler work costs £500. The firm must then partner with a licensed energy supplier, such as British Gas or E.ON, which may charge a £3,500 application fee to join their delivery network. According to the Energy Saving Trust, the firm can recover these costs through the first few installations, with each cavity wall job paying £600–£900 under ECO4 rates. Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6). Payback for the firm comes within 12–18 months if they complete 15 installations per year.
| Item | Figure |
|---|---|
| Upfront cost after grants | £8,500 |
| Yearly savings | £6,000 |
| Payback period | 1.4 years |
| 25-year lifetime savings | £150,000 |
What homeowners often get wrong
The most common mistake is assuming you can apply directly to the government to become an ECO4 provider, when in reality you must partner with a licensed energy supplier or join a TrustMark scheme. Here are three specific errors homeowners make when trying to enter the ECO4 market.
- Thinking you can register without certification Many assume a general builder or handyman can install ECO4 measures. The right answer is that you need PAS 2030:2019 certification from a body like MCS or BRE, or you risk voiding your warranty and losing grant funding worth thousands of pounds.
- Believing you can work with any supplier Some think any energy company will accept them as a delivery partner. The right answer is that only suppliers with over 250,000 domestic customers are obligated under ECO4, and you must negotiate a contract directly with them, or you miss out on £7,500 in BUS grants for heat pumps.
- Ignoring the TrustMark requirement Many skip registering with TrustMark, thinking it is optional. The right answer is that all ECO4 installations must be carried out by a TrustMark-registered firm, or you face enforcement action from Ofgem and potential bans from future schemes.
Quick reference
- Over 500 installer organisations are currently active in the ECO4 scheme across the UK, according to Ofgem figures from 2026.
- PAS 2030:2019 certification costs between £2,000 and £5,000 for most small installers, including audit and documentation fees.
- To be an obligated ECO4 supplier, you must have at least 250,000 domestic customer accounts as set by Ofgem regulations.
- Public Liability Insurance of at least £2 million is mandatory for all ECO4 installers before any work can begin.
- Gas Safe Register membership is required for any gas-related ECO4 work, with annual fees starting at £500 for a sole trader.
Frequently Asked Questions
No, you cannot apply directly to the government. You must partner with a licensed energy supplier or join a government-authorised certification body, as confirmed by Ofgem.
You need PAS 2030:2019 certification from an accredited body such as MCS for heating measures or TrustMark for wider retrofit work. Ofgem requires this for all ECO4 installations.
Ofgem reports over 20 energy suppliers and 500 installer organisations are currently active in the ECO4 scheme as of 2026.
