TrustMark vs HIES: which installer protection matters

TrustMark and HIES are not competing badges and they are not the same thing. TrustMark is the government endorsed quality scheme itself, described in its own scheme rules as the only UK Government Endorsed Quality Scheme¹. HIES is a TrustMark Scheme Provider: a body that operates and manages the quality scheme under which its registered businesses are registered, including oversight of standards and complaint handling¹. So a householder choosing an installer is not choosing between two rival marks. They are looking at one mark, delivered through one of several providers.

The practical difference matters most when something goes wrong. TrustMark does not investigate individual complaints or award compensation¹. The scheme provider does that. Where a provider's handling is in question, the matter can be referred to TrustMark, which may review whether the correct procedures have been followed by the provider¹. That is a review of process, not a second opinion on the workmanship.

For a household, the value of the mark is that it is tied to standards and to a route for redress, not that it guarantees a particular outcome. Installers under UK Government schemes must be TrustMark registered and/or Microgeneration Certification Scheme (MCS) certified², and TrustMark's framework requires compliance and certification with PAS 2035:2019 and PAS 2030:2019 for all relevant ECO measures³.

TrustMark and HIES are different things: one is the mark, the other a scheme provider

The distinction is structural. TrustMark is operated by TrustMark (2005) Limited, a company registered in England and Wales with company number 05480144⁶. That company runs the scheme of that name⁸. It is not a membership club for installers and it does not carry out the work of registering them day to day.

HIES sits underneath that structure as a TrustMark Scheme Provider¹. In that role it operates and manages the quality scheme under which TrustMark Registered Businesses are registered, including oversight of standards and complaint handling¹. A householder who books a business registered through HIES is dealing with a TrustMark registered business, reached through a particular provider.

That layered arrangement is why the two names appear together so often and why they are so easily confused. The mark is the assurance a householder recognises. The provider is the organisation that actually holds the register entry, checks standards and takes the first pass at a complaint.

It also explains why the answer to "which one protects me" depends on the stage of the job. Before work starts, the mark is what a householder checks. After work starts, the provider is who a householder deals with. TrustMark's own published benefits for homeowners include government endorsed quality, robust consumer protection, a TrustMark Online Directory, competent and quality work backed by guarantees, a Customer Charter, Trading Standards integration, free advice and information, and verified consumer reviews⁹.

For energy independence, this is a governance layer rather than a technical one. It does not make a home generate its own power or heat. What it does is attach a route to redress to work that a household cannot easily inspect or judge for itself, which is the main protection a homeowner has when spending on insulation, heating or renewables.

What TrustMark actually guarantees a household

TrustMark is a government endorsed quality scheme¹⁰, and the scheme's own material describes it as the only Government endorsed scheme for domestic trades⁹. That endorsement is the core of what it offers. It is not a warranty, an insurance policy or a compensation fund.

What it brings is a set of published benefits: government endorsed quality, robust consumer protection, the TrustMark Online Directory, competent and quality work backed by guarantees, a Customer Charter, Trading Standards integration, free advice and information, and verified consumer reviews⁹. Those are the scheme's own words about what a householder can expect.

The standards behind the mark are where the substance sits. TrustMark's framework requires compliance and certification with PAS 2035:2019 and PAS 2030:2019 for all relevant ECO measures³. Those are the retrofit standards that govern how measures are assessed, designed and installed. The Scottish Government's quality assurance statement records that the Business and Regulatory Impact Assessment estimated there would be an increase in costs associated with TrustMark approvals and compliance, but judged that the value of ensuring work is done to high standards and with consumer protection outweighed that increase¹¹.

The mark is also used as a gatekeeper in public schemes. Installers under UK Government schemes must be TrustMark registered and/or MCS certified². Under ECO, installers must be TrustMark accredited and will have a registration number, except in the case of installers of district heating connections⁵. For innovation measures under ECO, all such measures must be lodged with TrustMark (or an equivalent) and delivered by TrustMark (or an equivalent) registered businesses¹².

What that means in practice is that the mark is a condition of access to public money, not a guarantee of a good job. It raises the floor. It does not remove the need to check the register, keep paperwork and know the complaint route.

What HIES is: a TrustMark Scheme Provider and what that means for you

HIES is a TrustMark Scheme Provider¹. That single line carries most of the practical weight for a householder, because it determines who handles a problem.

As a provider, HIES operates and manages the quality scheme under which its registered businesses are registered, including oversight of standards and complaint handling¹. So when a business registered through HIES does poor work, the complaint goes through the provider's process rather than to TrustMark directly.

There is a second layer above that. The matter can be referred to TrustMark, which may review whether the correct procedures have been followed by HIES as the Scheme Provider¹. That is a procedural review. It is not a re-inspection of the installation and it is not a compensation route.

HIES publishes a contact telephone number of 0344 324 5242¹⁶. TrustMark publishes general enquiries on 0333 555 1234¹⁷. Both are published contact routes rather than complaint outcomes, and neither is a substitute for the guarantee that sits behind the work.

The guarantee is the part that matters most when an installer has stopped trading. Government guidance on faulty ECO4 and Great British Insulation Scheme installations states that families affected should first contact the installer who carried out the installation, and where the installer is no longer trading or unable to remedy damages, they can contact their guarantee provider to initiate a claim¹⁸. That route exists independently of the scheme provider's complaint handling.

For a household, the sequence is therefore: installer first, then guarantee provider if the installer is gone, then the scheme provider's complaint process, then TrustMark if the provider's process itself was not followed. Each step has a different job.

Where to complain when an installation goes wrong

The starting point is the installer. Government guidance is explicit that affected families should first contact the installer who carried out the installation, and where the installer is no longer trading or unable to remedy damages, they can contact their guarantee provider to initiate a claim¹⁸.

Where the complaint is separate from the main installation, official guidance on poor quality wall insulation says a householder can follow the steps set out in the TrustMark complaints process¹⁹. That process runs through the scheme provider for a business registered with one.

Where the installer is registered through HIES, the provider handles the complaint as part of its oversight of standards and complaint handling¹. If the provider's procedures were not followed, the matter can be referred to TrustMark for a review of that process¹.

Alongside the installer and scheme routes, there is the energy supplier and network route. The Citizens Advice consumer service may refer a householder to the Extra Help Unit if they need support with a difficult or urgent complaint, cannot deal with their energy supplier on their own due to personal circumstances, are considered vulnerable, or are at risk of being disconnected from an energy supply²⁰. That referral route is aimed at supplier and supply problems rather than installation quality, but it is part of the wider picture.

For households in Northern Ireland, NI Energy Advice provides referrals to energy grants and other sources of help²¹. In Wales, the Welsh Government has published a written statement on support for householders impacted by the closure of the Energy Company Obligation scheme²², and local authority pages set out ECO flexibility funding routes¹⁷.

The pattern across all of these is the same: the first contact is the party that did the work, and the escalation routes are procedural rather than compensatory.

Citizens Advice's call for a single, mandatory accreditation scheme

The current arrangement is layered, and the government has consulted on replacing it. The consultation on reforming consumer protection for home upgrade schemes proposes a transparent public register of government approved installers, a single advice and support service covering the entire time a home is being upgraded, powers to hold installers and delivery partners to account including bans from working on government schemes, and a new data-backed system that spots risks and installer performance issues earlier²³.

The proposed integrated consumer protection service would deliver unified, end-to-end consumer services and assurance processes for all DESNZ-supported home upgrades, bringing together responsibilities for all retrofit measures under one service, with many functions currently carried out by TrustMark and MCS instead performed by the new service²⁴.

Citizens Advice responded to that consultation on 10 September 2026, welcoming the opportunity and supporting centralised oversight, stronger installer standards, simplified redress, independent advice and mandatory consumer protection across the home energy upgrades market²⁵. That is the consumer body's position: one scheme, mandatory, rather than a set of overlapping providers.

The direction of travel matters for households planning work now. The current system requires TrustMark registration and/or MCS certification for installers under government schemes², and ECO installers must be TrustMark accredited with a registration number⁵. If the proposed service is created, many of those functions would move. Until then, the existing structure is what a householder is working with.

How this fits the wider consumer protection picture for home upgrades

Installer accreditation is one layer of a wider set of protections, and it is worth being clear about which layer does what.

General consumer rights apply to work done in a home, and the government publishes consumer protection rights covering England and Wales²⁶. Those rights exist regardless of whether an installer holds a mark.

Public funding schemes add their own conditions. The Home Upgrade Grant statistical release covers measures installed, homes upgraded, installation rates, installations by region, local authority and parliamentary constituency, carbon, bill and energy savings, and changes in Energy Performance Certificate ratings²⁷. That monitoring is how delivery is tracked, and it is separate from any individual complaint.

Local authority routes also exist. Bristol City Council publishes grant and loan routes for improving home energy efficiency¹⁰, and Ceredigion publishes ECO flexibility funding information¹⁷. These sit alongside the national schemes rather than replacing them.

For energy independence, the honest position is that accreditation does not reduce a household's dependence on the grid, a supplier or a fuel. What it does is attach accountability to work that a household cannot verify itself. A retrofit measure installed badly can underperform for years, and the household has no easy way to tell. The mark, the standards behind it and the complaint route are the mechanisms that make that risk manageable rather than invisible.

The limits are real. TrustMark does not investigate individual complaints or award compensation¹. The guarantee provider is the route when an installer has stopped trading¹⁸. The scheme provider handles the complaint in the first instance¹. And the government has consulted on replacing much of this with a single service²⁴. A householder weighing up an installer is therefore weighing a system in transition, not a settled one.

Getting help: Citizens Advice contacts and referral routes

The Citizens Advice consumer service is the main published advice route for England and Wales. The number is 0808 223 1133, with a textphone on 18001 followed by the helpline number²⁸, and opening hours of Monday to Friday, 9am to 5pm⁴. A Welsh language line is published on 0808 223 1144⁴.

There is a separate general advice line on 0808 278 7932, described as free and impartial help and advice¹⁷. In England, a further number is published on 0808 144 8844²⁹.

The consumer service covers consumers in England and Wales³⁰, and is described as a free consumer service for people in England or Wales with problems with energy bills or supply³¹. Its published scope includes information and support on struggling to pay bills, problems with your energy supplier or supply, saving energy at home and getting a better energy deal²⁹.

Referral is the key mechanism. The consumer service may refer a householder to the Extra Help Unit if they need support with a difficult or urgent complaint, cannot deal with their energy supplier on their own due to personal circumstances, are considered vulnerable, or are at risk of being disconnected from an energy supply²⁰. The Energy Ombudsman also publishes advice for consumers worried about their energy bills³².

For installation disputes specifically, the TrustMark route is published as an email address, disputes@trustmark.org.uk, and an online form at trustmark.org.uk/homeowner/support/ces²². The Department for Energy Security and Net Zero has confirmed that it nominated TrustMark to directly support customers of the Energy Company Obligation scheme²².

For households in Scotland, the Scottish Government publishes a heat in buildings quality assurance statement covering standards for work¹¹. For Northern Ireland, NI Energy Advice provides referrals to energy grants and other sources of help²¹. For Wales, the Welsh Government's written statement covers support for householders impacted by the closure of the Energy Company Obligation scheme²².