Learning how to become an ECO4 installer starts with a deadline: the scheme now runs until 31 December 2026, a nine month extension the government confirmed after a consultation. That consultation drew 215 responses from suppliers, installers and trade bodies (Energy Trust, 2026). For UK heating and insulation businesses, that gives a fixed window to get certified, registered with an obligated supplier and delivering measures before the scheme winds down in favour of the Warm Homes Plan.
Getting there involves several separate approvals rather than one application. Every installer needs TrustMark registration, most measures require PAS 2030 or PAS 2035 certification through a UKAS accredited certification body, and renewable technologies such as heat pumps and solar PV additionally need MCS certification (Ofgem, 2026; MCS, 2026). This guide walks through each requirement, what it costs, how long it takes, and how to actually get onto a supplier's contractor list.
Key Takeaways
- ECO4 has been extended to 31 December 2026, with no increase in delivery targets and no carry-over into a successor scheme (Energy Trust, 2026).
- TrustMark registration is mandatory for almost every ECO4 installer, with a £40 annual TrustMark fee plus separate Scheme Provider fees (TrustMark, 2026).
- Insulation and heating measures generally require PAS 2030:2023 installer certification and PAS 2035:2023 retrofit coordination, both mandatory since 31 March 2025 (Brighter Compliance, 2025).
- Heat pumps, solar PV and battery storage under ECO4 require MCS certification in addition to TrustMark (MCS, 2026).
- TrustMark itself now advises against joining solely to chase ECO4 work, since the scheme is in its final stages and GBIS has already closed (TrustMark, 2026).
What Does It Take to Become an ECO4 Installer?
Becoming an ECO4 installer means stacking three types of approval: business level TrustMark registration, measure level PAS 2030/2035 or MCS certification, and a working relationship with at least one obligated energy supplier who will contract your work (Ofgem, 2026). None of these bodies certify you for ECO4 directly. Instead, ECO4 sits on top of certifications that already exist for retrofit and renewables work more broadly.
That layered structure catches out a lot of new entrants. A Gas Safe registered heating engineer, for example, cannot install a heat pump under ECO4 on Gas Safe credentials alone. They need MCS certification for the heat pump itself and TrustMark registration for the business before any obligated supplier will put them on a contractor list (Ofgem, 2026). Insulation only firms face a parallel stack: PAS 2030 installer certification plus a recognised guarantee body such as CIGA for cavity wall work.
TrustMark Registration: The Non-Negotiable First Step
TrustMark registration is required for practically every ECO4 installer, with the sole exception of installers connecting district heating systems that are not linked to a shared ground loop (Ofgem, 2026). You cannot apply to TrustMark directly. Registration runs through one of more than 40 licensed Scheme Providers, trade associations and certification bodies that vet your competence before TrustMark adds you to its register.
The direct TrustMark fee is a modest £40 a year, but Scheme Providers set their own assessment and membership charges on top, and those vary by trade and business size (TrustMark, 2026). If you already need PAS certification for retrofit work, TrustMark expects that to come first. Its own guidance states you must gain PAS or MCS certification through a relevant certification body before a Scheme Provider will issue TrustMark registration for those trades (TrustMark, 2026). Our guide to becoming a TrustMark registered business breaks down that application sequence in more detail.
Do You Need PAS 2030 and PAS 2035 Certification?
Yes, for almost any insulation or heating measure delivered under ECO4. PAS 2035:2019 set the original whole house retrofit standard, and the updated PAS 2035:2023 and PAS 2030:2023 versions became mandatory from 31 March 2025 after a transition period (Brighter Compliance, 2025). PAS 2030 governs the physical installation, while PAS 2035 governs the assessment, design and coordination of the retrofit project as a whole.
Every ECO4 project needs a retrofit assessment, a retrofit coordinator and, where relevant, a retrofit designer overseeing the works, on top of the certified installer doing the physical job (nef, 2025). One notable change under the 2023 revision is that retrofit coordinators can no longer also act as retrofit designer on the same project, unless they hold separate, widely recognised design qualifications. That pushes many small firms toward subcontracting the role rather than training for it in house.
ECO4 also carries a minimum improvement rule tied to PAS 2035. Any property starting in SAP band F or G must be improved to at least band D, and any property starting in band D or E must reach at least band C (Ofgem, 2026). Installers who only think in terms of a single measure, one loft top up, for instance, often underestimate how much extra work that band jump can require once a proper assessment is done.
Is MCS Certification Required for Heat Pumps and Solar Under ECO4?
Yes. To appear on an obligated supplier's ECO4 contractor list for renewable technologies, an installer needs MCS certification for the specific technology. That could be an air source heat pump, ground source heat pump or solar PV system, and it comes alongside TrustMark registration for the business as a whole (MCS, 2026). MCS is currently mid-transition to a redeveloped installer scheme, which is worth factoring into your planning timeline rather than assuming the current process stays static.
Cost and timeline for MCS certification vary by technology and certification body, and depend heavily on how much of your team already holds relevant qualifications. We cover the full process in our guide to how to become MCS certified and break down realistic budgeting in our MCS certification cost guide, including where the redeveloped scheme changes what you need to budget for (MCS, 2026). If you are weighing up joining an existing umbrella scheme instead of certifying independently, our piece on the MCS umbrella scheme model covers that trade-off too.
What Do ECO4 Insulation Installers Need Specifically?
ECO4 insulation installers need PAS 2030:2023 certification for the measure type they install, plus TrustMark registration. They also need a recognised 25 year guarantee on every job, through a body such as CIGA, the National Insulation Association or the British Board of Agrément (CSE, 2026). All insulation installed under ECO4 has to carry a TrustMark approved guarantee, which is separate from the PAS certification itself and typically arranged through the guarantee body rather than the certification body.
Cavity wall and external wall insulation are the measures where this stacking is most visible. An installer might hold PAS 2030 certification for cavity wall work, be TrustMark registered, and still need a live CIGA membership before an obligated supplier accepts their paperwork, because the guarantee protects the homeowner if the installer later ceases trading. Skipping the guarantee step is one of the more common reasons applications get bounced back at the supplier stage.
How Do You Apply to Deliver Measures Under the ECO4 Scheme?
There is no single ECO4 scheme application form for installers to fill in with Ofgem directly. Instead, once TrustMark registered and appropriately certified, you contact an obligated energy supplier such as British Gas, E.ON or Octopus and ask to join their contractor or ECO4 delivery network (Ofgem, 2026). The supplier then runs its own due diligence before adding you.
Suppliers typically request evidence of TrustMark registration, PAS and MCS certificates where relevant, public liability insurance, and financial protection arrangements before onboarding an installer (Ofgem, 2026). Because suppliers set their own paperwork and pace, timelines vary considerably. Building a clean, complete certification file before approaching a supplier tends to shorten this stage more than anything else you can control.
ECO4 Installer Certification Costs and Timelines at a Glance
- TrustMark registration: Certifying body: TrustMark, via a licensed Scheme Provider; Applies to: All ECO4 measures (with minor exceptions); Approx. cost: £40/year TrustMark fee plus Scheme Provider fee, which varies (TrustMark, 2026); Approx. timeline: Provider dependent; TrustMark advises following up after 10 days
- PAS 2030:2023 installer certification: Certifying body: UKAS accredited certification body; Applies to: Insulation and heating measure installation; Approx. cost: Varies by measure and certification body; Approx. timeline: Weeks to a few months, including audit
- PAS 2035:2023 retrofit coordination: Certifying body: ABBE, City & Guilds and similar awarding bodies via training providers; Applies to: Whole house retrofit assessment and coordination; Approx. cost: Course and assessment fees vary by provider; Approx. timeline: Several weeks to a few months, modular delivery
- MCS certification: Certifying body: MCS approved certification body; Applies to: Heat pumps, solar PV, battery storage; Approx. cost: See our MCS certification cost guide for a full breakdown; Approx. timeline: See our how to become MCS certified guide
- Insulation guarantee registration: Certifying body: CIGA, NIA or British Board of Agrément; Applies to: Cavity wall and external wall insulation; Approx. cost: Membership and guarantee fees vary by body; Approx. timeline: Ongoing membership; 25 year guarantee issued per job
Common Mistakes When Becoming an ECO4 Installer
The most frequent misstep is treating TrustMark as the finish line rather than a checkpoint. Firms register with TrustMark first, then discover a Scheme Provider will not confirm their status until PAS or MCS certification for the relevant trade is already in place. That adds weeks of delay that could have been avoided by sequencing certification before registration.
A second common mistake is joining TrustMark purely to chase ECO4 work without checking scheme timing first. TrustMark's own guidance now tells applicants not to apply solely for ECO4 or GBIS purposes, since GBIS has closed and ECO4 is in its final stages ahead of the Warm Homes Plan (TrustMark, 2026). In practice, installers who plan for the Warm Homes Plan pipeline from the outset, rather than treating ECO4 as a standalone goal, tend to get more value from the same certifications over the following years.
Is It Still Worth Becoming an ECO4 Installer in 2026?
For most heating and insulation businesses, yes, provided the certification investment is framed around the wider retrofit market rather than ECO4 alone. The scheme still has genuine volume left before December 2026, and the certifications required, TrustMark, PAS 2030/2035 and MCS, all carry over directly into the Warm Homes Plan and related programmes such as the Warm Homes Local Grant (Energy Trust, 2026).
Homeowners researching the grant side of this, rather than the installer route, are usually better served by our separate guide to the ECO4 grant, which covers eligibility and what measures are typically funded. For installers managing multiple certifications, measure types and supplier relationships at once, proposal and system design software such as Reonic can help. It takes some of the administrative load off quoting solar and heat pump jobs, leaving more time for the certification work itself.
Frequently Asked Questions
How long does it take to become an ECO4 installer? Timelines depend on which certifications your business already holds. A firm starting from scratch, needing PAS 2030, PAS 2035 retrofit coordination and TrustMark registration, should budget a few months rather than weeks, since certification bodies require audits and Scheme Providers process applications at their own pace (TrustMark, 2026).
Can you become an ECO4 insulation installer without MCS certification? Yes. MCS certification only applies to renewable technologies such as heat pumps, solar PV and battery storage. ECO4 insulation installers instead need PAS 2030:2023 certification for their measure type, TrustMark registration, and a recognised guarantee through a body such as CIGA or the National Insulation Association (CSE, 2026).
What happens to ECO4 installers after the scheme ends in December 2026? The government has confirmed no increase in delivery targets and no carry-over arrangements beyond 31 December 2026 (Energy Trust, 2026). Certified installers are expected to transition into the Warm Homes Plan, which government has framed as a £15 billion successor programme covering similar measures.
Do you need to work directly with an energy supplier to deliver ECO4 measures? Yes. There is no route to deliver ECO4 measures without an obligated supplier contracting the work, since suppliers carry the compliance obligation and run their own due diligence on contractors (Ofgem, 2026). Certification alone does not generate ECO4 work without that supplier relationship in place.
Is TrustMark registration enough on its own to start ECO4 work? No. TrustMark registration is necessary but not sufficient. Most measures also require PAS 2030/2035 certification, and renewable technologies require MCS certification on top of TrustMark, before an obligated supplier will add an installer to its contractor list (Ofgem, 2026).
