Faulty energy efficiency installations

Nearly one year after the problems emerged, around 3,000 homes with defects had been found and fixed out of the more than 30,000 homes estimate to be affected. TrustMark, the government-endorsed quality scheme, did not notify the Department of high levels of faulty installations of external wall insulation until October 2024, more than two years after the start of ECO4 in April 2022. It highlighted similar concerns with internal wall insulation in November 2024. By mid-September 2025, nearly one year later, less than 10% of the estimated total number of affected homes had been found and fixed.1 TrustMark will oversee the programme to find and fix the remaining homes with faulty external 1 This is based on the midpoint of the estimated range of 32,000 to 35,000. 2,934 remediated homes / 33,500 = 9%. 3 wall insulation, of which it estimates there are around 20,000 as of November 2025. It expects to have audited all relevant homes (providing access is granted) within 15 months of when we took evidence in November 2025. TrustMark and the retrofit sector face a serious challenge in scaling-up audit activities at the pace necessary to meet these timescales. The Department plans to identify faulty internal wall insulation through existing audit processes, but we fear it may be overconfident in expecting this approach to be adequate. It is vital that the remaining homes with defects are found and fixed as soon as possible. As waiting times increase, the likelihood of damage occurring increases, and there are immediate health and safety risks that need urgent attention. recommendation a. In its Treasury Minute response, the Department should set out how it plans to scale-up its find-and-fix programme to meet the 15-month ambition and how it will find all the faulty internal wall insulation. b. Given the severity of the issue for residents of affected homes, the Department should be seeking to deliver the find-and-fix programme within a much shorter timeframe and should updat

Households do not have real assurance the government will protect them from unaffordable bills when the original installer or guarantees do not cover the cost of repairs. Ministers have stated that no household should have to pay to fix the issues. The original installer is liable for fixing the installation and costs up to £20,000 should be covered by a guarantee when the installer has ceased to trade or fails to remediate. This process leaves some households unprotected. Remediation costs will sometimes exceed the guarantee cap. It should normally cost between £250 and £18,000 per home to correct the installation, but in the worst case we are aware of it cost over £250,000 to fix the defects and resultant damage. We are sceptical that the original installers and the guarantee providers will be able to withstand the potential scale of claims. Households have not yet claimed on guarantees in large numbers, but not all installers are complying with the remediation process, and some company directors are closing and restarting their businesses to avoid remediation responsibilities. The Department plans to bring ECO partners together to find bespoke solutions for the “very small number” of households it anticipates will not be sufficiently covered under standard processes. We find neither the Department’s proposed solution nor its downplaying of the likely scale 4 of the problem at all credible. Since we took evidence in November 2025, the government has announced that it will end ECO. There will be no additional obligation beyond the existing ECO4 and GBIS targets and no levy on bills from April 2026, although the Department is yet to confirm whether it will extend the period for suppliers to meet their existing ECO4 obligations beyond March 2026. We are concerned there may not be a big enough retrofit market once ECO ends to ensure enough installers remain viable businesses able to complete the remediation. recommendation Given the urgency of this matter, the Departm

The Department’s senior officials took two years to recognise the scale of the problems, which led to many faulty installations that could have been avoided. This is unacceptable and demonstrates very poor overall supervision. The Department acted in October 2024 when TrustMark informed it of analysis indicating high levels of non-compliance with quality standards in external wall insulation. TrustMark only developed the analytical capabilities for interrogating its data and producing this kind of analysis in the latter half of 2024–prior to this it did not have the resources or systems to oversee what was happening on the ground. The Department should have done the due diligence on this before Trustmark were appointed to this role, however, the Department had access to other information that should have alerted it to the potential issues much earlier given that the ECO4 scheme started in April 2022. For example, TrustMark told us it had been sharing the results of its audits with the Department from 2022 and that when it started to identify the increased risk from 2023 into 2024, it undertook more audits to better 5 understand the level of risk. The Department’s failure to take minutes of its meetings with TrustMark meant it was unable to defend its position that it had not been alerted sooner. The Department also had risks to quality, assessments and standards on its programme risk register since November 2022 but did not take any proactive steps to prevent the risks materialising in the first place or escalate the risks appropriately. The Department gave the scheme virtually no senior level attention and should have carried out far more investigations much sooner. Its poor oversight of ECO4 and GBIS meant that senior leaders had assumed the quality assurance system was working when it was not. recommendation The Department should review its risk management and internal escalation systems so that issues identified within specific schemes are escalated swiftly and

The Department’s system of quality assurance and consumer protection was far too complicated, and organisations within it focused too much on their own tasks rather than whether the system was protecting consumers. The ECO schemes and the retrofit quality assurance and consumer protection system combine to make a system that is too layered, fragmented and complicated. The Department accepts there were “serious failings at every level” and the system “has not provided the protection that consumers deserve”. Responsibilities were unclear and organisations focussed on their individual roles within the complex system, rather than taking a step back to critically assess the system and identify risks and design flaws. For example, none of the expert organisations involved spotted that the move from a single- measure to multi-measure scheme would add delivery complications and therefore risk. TrustMark accepts it should have realised much sooner that the system design under-estimated the level of risk involved. The United Kingdom Accreditation Service (UKAS), which accredits the retrofit installer certification bodies, apologises for its “role within the system”. We welcome the organisations accepting some responsibility, but it is not good enough for organisations holding so much expertise and knowledge to say they delivered on their specific responsibilities and instead blame the system of which they were a key part. recommendation The Department should publish an annual report to Parliament on all its retrofit schemes, their level of non-compliance and estimated fraud, and whether or not the schemes are working as intended. 6

The Department did not give the risk of fraud appropriate priority, and it is likely that the known levels of fraud are a significant under-statement of the true level of fraud. No single organisation has overall responsibility for preventing and detecting fraud on ECO4 and GBIS. The Department did not carry out a fraud risk assessment during the design of ECO4 and the ownership of some known fraud risks was agreed only in October 2025. Ofgem’s role in relation to fraud is limited to progressing counter-fraud investigations where allegations have been made. Yet no organisation is responsible for pro-actively looking for fraud, nor holds all the data it would require to do so effectively. Ofgem has identified installations worth 1.75% of the scheme value as fraudulent but, given the above, we suspect the true level of fraud to be much higher and above the Departments tolerance threshold of 2%. If the Department had paid more attention to preventing and detecting fraud, it would likely have avoided some of the poor quality installations too. We suggest that the Serious Fraud Office should look at this case. recommendation a. Given the likely role of fraud in the poor quality installations, the Department should refer the issue to the Serious Fraud Office to investigate the extent of fraud across ECO and bring criminals to justice. b. HM Treasury should extend its requirement in Managing Public Money for a Fraud Risk Assessment on all new major areas of public spend to include levy-funded schemes instigated by the government, such as ECO. c. In future schemes, the Department should ensure that one body is responsible for fraud prevention and detection at the system level, enabled by counter-fraud activities of and data from other organisations in the system. d. HM Treasury should amend its guidance in Managing Public Money to recommend public bodies design fraud out of all new schemes as far as is sensible, and have one body responsible for fraud prevention and detecti

The serious failings to protect consumers on these schemes risk undermining confidence in all the Department’s retrofit schemes. The Department believes it is rebuilding confidence through the steps it has taken to date, such as suspending 38 installer businesses, implementing a “robust” reinstatement process, and requiring retrofit coordinators to visit 7 each site in person. We are extremely sceptical that the changes so far are sufficient, especially given the low level of remediation that has taken place to date. For example, there is still no requirement for the retrofit coordinator to be independent of the installer, so the person who is meant to check the retrofit has been completed to the correct standard can be appointed by the installer they are assessing. The Department needs to make further changes before it can be confident there will be no more faulty installations under the current system. Since we took evidence in November 2025, the government announced that it would not continue ECO after the current schemes end, but that it would continue to invest in tackling fuel poverty through its Warm Homes Plan. It is vital, given the Departments strong statement that in the last resort it will stand by householders to ensure their homes are remediated that high priority is given to this pledge even after the scheme ends. The Department accepts that wholesale reform of the system is ultimately required to ensure customer protection and restore the public’s confidence in retrofits. It intends to deliver this reform in line with three principles: the system must be simpler and clearer; there must be stronger central oversight; and there must be clear accountability, redress and remediation when things go wrong. The public have a right to expect that where work is funded by government grant that the government effectively guarantee the work will be done correctly and put right if not. recommendation a. The Department should give high priority to ensuring—and ind

On the basis of a deeply concerning report by the Comptroller and Auditor General, we took evidence from the Department for Energy Security and Net Zero (the Department) and Ofgem to find out why an estimated 98% of external wall insulation and around a third (29%) of internal wall insulation fitted under the Energy Company Obligation 4 (ECO4) and the Great British Insulation Scheme (GBIS) up to mid-January 2025 have major issues that need fixing.2 We also took evidence from TrustMark and the United Kingdom Accreditation Service (UKAS).

We have received written submissions from a range of sources including voluntary sector organisations, local authorities, industry representatives and commercial organisations, and households that have been affected by poor quality work under ECO. A full list of the written evidence we received is available on the Committee’s website.13 Particular issues and concerns drawn to our attention include: 7 HM Treasury, Budget 2025, 26 November 2025 8 Letter from the Department of Energy Security & Net Zero, dated 2 December 2025 9 C&AG’s Report, paras 1, 4, 1.6 and 1.7 10 C&AG’s Report, Figure 4 11 C&AG’s Report, para 6 12 C&AG’s Report, para 19 13 Committee of Public Accounts, Faulty energy efficiency installations Written evidence 10 • the impact of poor quality and fraudulent installations on people’s health and wellbeing, and the inadequacy of the complaints and remediation process; • factors contributing to the failures on the current ECO schemes, and opportunities for improving oversight, incentives, regulation, accountability and competence across ECO and the quality assurance and consumer protection system; • recommendations for improving the remediation process to better protect consumers; and • the impact of these failures on the public’s perception of and confidence in retrofit measures, on the wider retrofit industry, and on our ability to achieve net zero. Failures with external and internal wall insulation

The Department and Ofgem believe that an estimated 98% of external wall insulation and around a third (29%) of internal wall insulation fitted under ECO4 and GBIS up to mid-January 2025 have major issues that need fixing. Between 32,000 and 35,000 homes are likely to be affected. This is based on audits of a statistically representative sample of 758 homes that had external and internal wall insulation installed under ECO4 and GBIS before mid-January 2025. The site visits, which were commissioned by Ofgem, took place between June and August 2025.14

The audits found: • 98% of homes with external wall insulation have major issues: 92% have defects that will negatively affect the insulation’s performance, often creating the risk of water ingress and mould; 6% have immediate health and safety risks, such as inadequate ventilation, and may also have other major issues requiring remediation. Between 22,000 and 23,000 homes are likely to be affected.15 • 29% of homes with internal wall insulation have major issues: 27% have defects that will negatively affect the insulation’s performance, often creating the risk of condensation and mould; 2% have 14 C&AG’s Report, paras 2.2 to 2.4 and Figure 10 15 C&AG’s Report, para 2.2 and Figure 10 11 immediate health and safety risks, such as inadequate ventilation and poor electrical safety, and may also have other major issues. Between 9,000 and 13,000 homes are likely to be affected.16 The Department does not have an estimate of how many additional homes retrofitted after mid-January 2025 are likely to have major issues, so the total number of homes affected will be higher than we set out in this report.17

The Department stressed to us that these failures include a spectrum of issues, from not getting the full benefit of a measure because of gaps in the insulation, through to more serious failings that have caused damp or mould or immediate risks to health and safety, such as an exposed electrical wire. However, it accepted that this level of failure is unacceptable.18

Faulty installations can have wider impacts on households, beyond just living in unsafe, damp or mouldy homes. Respondents to Ofgem’s survey of people who used its ECO helpline reported being left without central heating over winter and having to seek alternative accommodation, wider damage to their homes such as water damage to ceilings, and having to pay hundreds of pounds to replace carpets and repair decoration.19 Written evidence submitted to us by National Energy Action and Severn Wye Energy Agency highlighted the physical, emotional and financial distress that can be caused by retrofit failures.20 Zak Ashraf gave evidence to the Energy Security and Net Zero Committee in February 2025 about the failed ECO4 retrofit of his mother’s house–he described how his mother had had to move out of her home, and how he had lost sleep over and was exhausted from pursuing the drawn-out remediation process.21 Finding and fixing the defects

To limit further faulty installations, the Department asked the certification bodies and scheme providers, via TrustMark, to suspend installer businesses based on their failure rate. By the end of January 2025, 38 installers had been suspended, preventing them from carrying out new work of this kind under government schemes.22 The Department told us this represented 81% of the external wall insulation market and that 22 installers had been re-instated by the time we took oral evidence in November 2022, 16 C&AG’s Report, para 2.3 and Figure 10 17 C&AG’s Report, para 2.6 18 Q 75 19 C&AG’s Report, Figure 7 20 FEE0003, FEE0021 21 Energy Security and Net Zero Committee Oral evidence: Retrofitting homes for net zero, HC 453, 12 February 2025 22 C&AG’s Report, para 2.13 12 after having fixed the identified defects for which they were responsible.23 However, this reinstatement process only covers remediation work identified by the audit of 1,109 external wall insulation installations, before it was understood how widespread the major failures against the quality standard were.24

The National Audit Office reported that, as of 11 September 2025, 2,934 homes with external and internal wall insulation with major issues had been remediated.25 This means less than 10% of the estimated 32,000 to 35,000 homes with major issues had been found and fixed almost one year after TrustMark notified the Department of its concerns in October 2024.26 In written evidence sent to us following the oral evidence session, the Department confrmed that 4,603 homes had been found and fixed by 7 November 2025. However, the Department did not specify whether this includes homes that had minor issues only.27 It therefore may not be comparable to the estimate of 32,000 to 35,000 homes needing remediation due to major issues. Minor issues may affect insulation performance over time, such as weak points in insulation around gas supply pipes, or may not materially affect the insulation at all, such as missing documentation.28

Delays in finding and fixing these homes increase the risk of damage to the property, including damp and mould, and leave people in homes with unaddressed health and safety risks.29 We asked the witnesses how they would make sure the remaining faulty installations would be found and fixed in a timely way.30

The Department and TrustMark told us that TrustMark would oversee a find-and-fix process for homes with external wall insulation. It would offer audits to all homes with external wall insulation installed through ECO4 or GBIS, provide direct oversight to ensure the work is corrected, and work with local communities to build engagement and trust.31 TrustMark and the Department expected, at the time we took evidence in November 2025, all relevant homes to have been audited (providing access is granted) within 23 Q 82 24 C&AG’s Report, para 2.27 25 C&AG’s Report, Figure 10 26 This is based on the midpoint of the estimated range of 32,000 to 35,000. 2,934 / 33,500 = 9%. 27 Letter from the Department of Energy Security & Net Zero, dated 2 December 2025 28 C&AG’s Report, Figures 6 and 10 29 Qq 1, 75, 153; C&AG’s Report, para 2.19 and Figure 6; Energy Security and Net Zero Committee Oral evidence: Retrofitting homes for net zero, HC 453, 12 February 2025 30 Qq 70, 133-137 31 Qq 57, 61 ,76, 139, 151; Letter from TrustMark, dated 25 November 2025; The Department has provided more information on the audit process, including who is eligible and contact information, at: www.gov.uk/insulation-check 13 12 to 15 months.32 The Department told us that any defects identified should be fixed by installers within 12 weeks, although it accepted that this may take longer when the guarantee needs to be invoked. The Department said that “a lot of this” would be resolved within 18 months.33 In written evidence submitted to us after the oral evidence session, TrustMark estimated there were around 20,000 homes with faulty external wall insulation yet to be found and fixed.34 We believe this timescale is very optimistic which is one of the reasons we have recommended that the Department gives the Committee regularly six monthly updates on this matter.

The Department told us that it plans to identify faulty internal wall insulation through existing audit processes. First, TrustMark and the certification bodies continue to conduct business-as-usual audits. Second, households with concerns can contact their installer and certification body, or the ECO contact centre run by Ofgem, through which calls are triaged and audits arranged when necessary.35 We pressed the Department and Ofgem on how people will know if they have a problem with their insulation, as in some cases the defects may not yet have presented themselves as problems. Ofgem told us that concerns with internal insulation tend to manifest quickly.36 We also pressed all parties to confirm that they were encouraging people to be vigilant to defects and immediately report them. The Department confirmed that this was the case, and that both it and Ofgem had been working with their respective behavioural insights teams to ensure their communications were effective.37 The Department did not outline what would happen if this approach failed to find all homes with internal wall insulation defects, or how they could persuade more people to request audits. Protecting households from the cost of repairs

The original installer is liable for fixing the installation to meet the relevant standards. However, the National Audit Office reported that not all installers are complying with the remediation process.38 We asked TrustMark whether the process for installer businesses to become TrustMark-registered (and therefore be able to do work under government retrofit schemes) includes an assessment of the liquidity and financial 32 Qq 70, 71, 137 33 Qq 137, 138 34 Letter from TrustMark, dated 25 November 2025 35 Qq 139 - 142; C&AG’s Report, para 2.14 36 Qq 140, 141 37 Qq 141, 142 38 C&AG’s Report, paras 2.19 and 2.25 14 stability of installer businesses. TrustMark told us that it does not do a “full dive” into the liquidity and stability of a business, but that in most cases a business must have been trading for at least six months before it can be registered for a given area of work.39

The National Audit Office also reported that some company directors are closing and restarting their businesses to avoid remediation responsibilities.40 TrustMark told us it has developed a watchlist and can stop a new business operating until it has fixed the faulty work for which its directors were responsible under the previous business. TrustMark told us it was not working directly with Companies House or The Insolvency Service on these matters but, upon our prompting, accepted that it should do.41

Written evidence submitted to us by the Green Homes Group highlighted how some people are unlikely to trust the original installer to fix the issues they created.42 The Department said it is providing assurance to households by ensuring the installer is appropriately certified as competent to do the work, and by checking that the repairs had been done correctly.43

If the installer has ceased to trade or fails to fix the issues, remediation costs up to £20,000 should be covered by a guarantee.44 TrustMark confirmed in follow-up correspondence that these policies do not cover compensation for ill health or loss of earnings that might arise as a consequence of mould.45 The Department told us that households had not yet claimed on the guarantees in large numbers and that the installers were remediating the work.46

TrustMark told us that three organisations provided the bulk of the cover.47 In written evidence provided after the oral evidence session, the Department confirmed that the guarantee market for solid wall insulation is limited to three companies: QualityMark Protection, which provides regulated insurance-backed guarantees through SafeWorld; and SWIGA and CIGA/IAA, which are asset-backed guarantees.48

We asked the witnesses whether they had analysed the guarantee policy wording to ensure they did not include excesses or complex issues that render them useless in practice, or had reviewed the balance sheets of the 39 Q 64 40 C&AG’s Report, para 16 41 Qq 59, 60 42 FEE023 43 Q 151 44 Q 58; C&AG’s Report, para 15 45 Letter from TrustMark, dated 25 November 2025 46 Q 82 47 Q 68 48 Letter from the Department of Energy Security & Net Zero, dated 2 December 2025 15 cover providers. TrustMark and the Department told us that TrustMark’s financial protection panel, which consists of external independent members, had initially reviewed all guarantees to ensure they were fit for purpose, and that TrustMark had also been looking at the policies again over the last 12 months to ensure the affected homes were covered.49 In written evidence provided after the oral evidence session, the Department explained that to invoke a guarantee where the installer is still trading but has failed to rectify the problem, consumers must first work through TrustMark’s dispute resolution process. This includes escalating the dispute to the Dispute Resolution Ombudsman (DRO). If the DRO rules in the consumer’s favour, and the installer still fails to rectify the problem, the guarantee provider will at that point step in to remediate the property, assuming the guarantee in question has a “failure to rectify” clause.50 We are concerned that these processes will take too long especially where there are serious defects causing health issues of the occupants.

Where guarantees are invoked, the repairs will likely in some cases cost more than the £20,000 covered by guarantee. TrustMark advises it should normally cost between £250 and £18,000 per home to correct the faulty installations, if it can be done before major damage occurs. However, in the worst case we are aware of it cost over £250,000 to fix the defects and resultant damage.51

The Department told us that the Ministers are very clear these problems must be fixed at no cost to households who have done nothing wrong. It told us it expects only a “very small number” of homes to not be remediated by the original installer or covered by the guarantee. The Department told us it is “working hard to drive the system so that all parties come together” to identify bespoke solutions for these most challenging cases.52 We call on the Government where all other avenues have been exhausted to step in and ensure the defects are remediated even though they have now closed this scheme.

It is not clear the future retrofit market will be big enough to sustain businesses to meet the level of remediation required. Since we took evidence in November 2025, the government announced that it would end ECO, with no levies on bills from April 2026. It said it would continue investing to tackle fuel poverty through its Warm Homes Plan but did not provide any further detail.53 In written evidence provided to us after our oral session, the Department clarified that it was yet to formally confirm 49 Qq 64, 66, 67, 147 50 Letter from the Department of Energy Security & Net Zero, dated 2 December 2025 51 C&AG’s Report, para 2.19; Energy Security and Net Zero Committee Oral evidence: Retrofitting homes for net zero, HC 453, 12 February 2025 52 Q 76, 78, 82, 83 53 HM Treasury, Budget 2025, 26 November 2025 16 whether it would extend the period for suppliers to meet their existing ECO4 obligations beyond March 2026. However, there would be no additional obligation beyond the existing ECO4 and GBIS targets.54 The National Audit Office report shows that ECO is by far the largest retrofit scheme, with over 300,000 homes retrofitted via ECO4 and GBIS by the end of March 2025.55 54 Letter from the United Kingdom Accreditation Service, dated 27 November 2025 55 C&AG’s Report, Figure 8 17 2 Reasons for the failures Poor information and oversight

The National Audit Office reported that the Department designed both ECO and the consumer protection and quality assurance system to operate at arm’s length from government, and that the Department gave itself limited oversight and influence of ECO4 and GBIS. It concluded that the Department and Ofgem took quick action but this was only after TrustMark shared its analysis of high levels of non-compliance with quality standards in external wall insulation in October 2024.56 Witnesses at our oral evidence session indicated that other information should have alerted the Department to the issues much earlier.57 The National Audit Office concluded that the Department did not fully use the levers it did have to oversee ECO4 and GBIS, and that its poor oversight of the schemes meant senior officials assumed the quality assurance system was working when it was not.58 The Department accepted that it should have been more questioning and given the schemes more oversight, and that there were not enough installation checks.59

The National Audit Office reported that TrustMark only developed the analytical capabilities for identifying non-compliance trends in the latter half of 2024. Its funding model meant it did not have the free cashflow to develop these capabilities sooner.60 However, TrustMark told us it had been sharing the results of its audits with the Department in regular meetings since 2022, and started to identify the increased risk from 2023 into 2024, at which point it undertook more audits to better understand the level of risk.61 The Department believes that the Autumn and Winter of 2023–24 is also when the issues likely first became visible, after a ramp up of installations in the spring of 2023.62 UKAS and the Department also both told us that the intelligence that was available (for example data on installations, audit results and consumer complaints) was not being escalated or drawn together as it should have been to understand levels of 56 C&AG’s Report, paras 19 and 3.5 57 Qq 49, 52,55, 115, 116 58 C&AG’s Report, para 3.6 59 Q 89, 116, 117 60 C&AG’s Report, para 21 61 Qq 49, 52 62 Q 115 18 risk and non-compliance.63 Neither TrustMark nor DESNZ have been able to provide minutes of meetings which took place between 2022 and 2024, and the Department has written to us to say that it has no evidence that it was notified earlier than October 2024.

Since November 2022, the Department’s programme risk register had included risks to quality, assessments and standards, yet the Department did not take sufficient action to check whether the risks were materialising, to prevent them from happening, or to escalate the risks appropriately. In November 2022, the Department recorded a risk that TrustMark might not carry out compliance checks on time or to the correct standard. It identified the risk as high impact but “very unlikely” to materialise and therefore judged it was a risk it could tolerate and not escalate to the portfolio level. In June 2023, it identified a risk that failures in the wider compliance and assurance processes could limit installation quality. It judged this risk was of medium impact and “possible” to materialise.64 The National Audit Office found that the Department did not have a dashboard reporting against key delivery risks, and that it only escalated these concerns to its Net Zero Buildings Portfolio Board in January 2025, once they had materialised as issues.65 Complicated and siloed quality assurance and consumer protection system

The National Audit Office’s report considered by the Committee concluded that ECO4 and GBIS combined with the consumer protection and quality assurance system resulted in an overly complex system, with many different actors. It reported that nobody spoken to during its investigation could give a comprehensive explanation of how the system was meant to work, and that there was no central document clearly setting out how the system should operate across the different organisations and processes.66 In their written evidence submissions to us, Severn Wye Energy Agency, Fuel Poverty Action, Kingspan Insulation Ltd and UKAS identified this fragmentation and complexity as a contributing factor to the high level of faulty installations, as well as the difficulty people subsequently face in getting the defects fixed.67 UKAS described a “multi-tiered system” comprising “the accreditation; we accredit the certification bodies. 63 Qq 55, 116 64 C&AG’s Report, para 1.8 65 C&AG’s Report, para 3.5 and Figure 5 66 C&AG’s Report, para 3.8 67 FEE0003, FEE0025, FEE0010, FEE0022 19 The certification bodies then certify the installers. Those certification bodies are also TrustMark scheme providers. Then there is the installer and the retrofit co-ordinator—[ … ]” which “can work if there is a shared understanding of the mission and the risk that relates to it”.68

The Department told us it designed the consumer protection and quality assurance system in response to the 2016 Each Home Counts review, introducing a single quality mark (delivered by TrustMark) and higher standards that consider multi-measure retrofits in the context of the whole home.69 It told us that the new system worked “alongside and with the grain” of the UK’s existing, decentralised model of standards that relied on the private sector.70 However, the Department accepted that the system was “too layered, fragmented and complicated and has not provided the protection that consumers deserve”.71

We asked the witnesses why no-one warned the Department about the risks or flaws with the system it had designed, or considered whether the system as a whole was protecting consumers.72 While TrustMark accepted it should have done much more, Ofgem highlighted their limited role within the flawed system. • Ofgem accepted that the measures are complex to oversee and deliver, and that the supply chain is very complex, but it told us that the Department was responsible for the design of the scheme, including decisions on how to assess fraud.73 • TrustMark explained to us that, with hindsight, the move from a single-to multi-measure scheme introduced challenges and delivery complications, and therefore risk. It accepted it should have recognised during the design phase that the system under-estimated the level of risk involved,74 and they did not have the resources or digital infrastructure to do it at the time the scheme was launched.75 They and the Department should have recognised this and remediated this short coming much sooner. • UKAS explained to us that the level of audit required of certification bodies for new installers assumed a low level of risk, but that it ought to assume a high level of risk given what we now know. 68 Qq 16, 17 69 Department for Business, Energy & Industrial Strategy and Department for Communities & Local Government, Each Home Counts, December 2016. 70 Q 91 71 Qq 93, 144, 149 72 Qq 3, 18, 29, 56 73 Q 128 74 Qq 2, 14 75 Qq 2, 14; C&AG’s Report, para 21 20 Even though the audit level is set by the Department and not UKAS, we challenged that UKAS should have identified and raised the issue with the Department. UKAS told us it did so but confirmed in follow- up correspondence to us that this was not until February 2025. UKAS apologised for its “role within the system”.76 Insufficient focus on fraud risk

The Department did not complete a full fraud risk assessment before ECO4 was implemented in 2022. This became a mandatory requirement in Managing Public Money for any new major area of spend in March 2022, but it would still have been considered good practice at the time.77 The Department clarified that it had completed an initial fraud impact assessment during the ECO4 policy stage, but accepted that it had not done sufficient preparation and had initially failed to understand some of the scheme’s exposure to fraud. The Department confirmed that the fraud risk assessment had since been completed and was being actively managed, with all risks clearly allocated to owners as of October 2025.78

The Department explained that no single organisation has overall responsibility for preventing and detecting fraud on ECO4 and GBIS.79 Ofgem’s role in relation to fraud is limited to progressing counter-fraud investigations where allegations have been made.80 Ofgem explained to us that it has neither a legislative role nor the ability to detect fraud across the whole system. It told us it had identified installations worth 1.75% of the scheme value as fraudulent as of November 2025, which is below the 2% departmental threshold for fraud.81 However, this is detected rather than estimated fraud. The National Audit Office reported that Ofgem had estimated businesses could have fraudulently claimed between £56 million and £165 million from energy suppliers under ECO, which would be up to 3.9% of the £4.2 billion scheme delivery costs to the end of March 2025. It also reported that there were separate suspicions of other fraudulent activity that was not included in this estimate.82

Ofgem relies on energy suppliers, TrustMark, certification bodies and scheme providers to alert it to any suspicions of fraud. However, while these bodies have responsibilities to report fraud that they have identified, they 76 Qq 20, 28, 56; Letter from the United Kingdom Accreditation Service, dated 27 November 2025 77 Q 122; C&AG’s Report, para 4.10; HM Treasury, Managing Public Money, June 2025 78 Qq 122, 123, 125 79 Q 127 80 C&AG’s Report, para 4.12 81 Qq 128, 130, 131 82 C&AG’s Report, para 4.3 21 have no requirement to proactively look for fraud, and poor information sharing across the system hinders their ability to do so.83 For example, in its written evidence submission, Energy UK set out how more rapid dissemination of intelligence on fraud trends by Ofgem would help energy suppliers improve their fraud controls.84

We pushed Ofgem and the Department on what they were doing to actively look for fraud, and highlighted that fraud is likely contributing to the high level of defects on external and internal wall insulation.85 Written evidence submitted by members of the Green Homes Group (Ashden, Centre for Sustainable Energy, Citizens Advice, E3G, Friends of the Earth and Greenpeace) reported that people have experienced fraud and intentional bad practice as part of their faulty retrofits.86 The Department assured us that it is “bringing together the parties that might have information that would allow Ofgem to identify cases of potential fraud.” It explained that it is working to make sure data about households—such as their likely eligibility for schemes—can be shared across the system. It also told us that TrustMark had introduced different software systems that enable it to identify potentially fraudulent installations from the data it holds.87 Addressing current issues and reforming the system for the future

Written evidence from the Royal Institution of Chartered Surveyors, the End Fuel Poverty Coalition, AgilityEco and the Green Homes Group told us how the failures with ECO are undermining public confidence in retrofits, potentially with negative impacts on our ability to reduce both fuel poverty and carbon emissions.88 The Department told us it is “tightening up” the current system, and that it expects this to help rebuild the public’s confidence in the ECO schemes and wider retrofits.89 It told us, for example: • As of March 2025, it is a requirement for retrofit coordinators, who manage the design and installation of the measures, to physically visit each project site to help ensure the design is appropriate for the specific property.90 83 C&AG’s Report, para 4.12 84 FEE0019 85 Q 131 86 FEE0023 87 Q 132 88 FEE0014, FEE0015, FEE0016, FEE0023 89 Qq 97, 99, 100 90 Q 99 22 • Organisations across the system are working together to share information and collectively make more informed decisions.91 • TrustMark and the certification bodies suspended 38 installer businesses, representing 81% of the external wall insulation market. As of November 2025, 22 installers had been fully reinstated after meeting requirements on TrustMark’s “robust six-point plan”, including full remediation of the problems identified.92

We pressed the Department on a key outstanding design flaw: retrofit assessors (who provide information about a home’s energy performance) and retrofit coordinators (who manage the project and should check the retrofit is completed to the correct standards) can be appointed and contracted by the installer they are assessing.93 The National Audit Office reported that retrofit coordinators may therefore be incentivised to approve non-compliant installations to maintain business with installers.94 We also received evidence from a range of organisations highlighting this as a key weakness that must be addressed.95 The Department agreed that there is not enough independence between these roles under the relevant standard (PAS 2035).96

Ultimately, the Department made its position very clear. It told us there were “serious failings at every level of the system that are systemic” and that it intends to reform the system to better protect consumers.97 Since we took evidence in November 2025, the government announced that it would end ECO, with no levies on bills from April 2026, but that it would continue to invest in tackling fuel poverty through its Warm Homes Plan.98 The Department told us that Ministers had set out three principles for future reform of the system: the system must be simpler and clearer; there must be stronger central oversight, including a much stronger expectation to get things right the first time and appropriate sanctions; and there must be real accountability, with clear redress and remediation when things go wrong. It plans to provide further detail on the reforms in its Warm Homes Plan.99 91 Q 100 92 Qq 82, 100, 102 93 Q 111; C&AG’s Report, Figure 4 and para 4.9 94 C&AG’s Report, para 4.9 95 FEE003, FEE0010, FEE016, FEE0019, FEE0025 96 Q 111 97 Qq 97, 144 98 HM Treasury, Budget 2025, 26 November 2025 99 Qq 97, 98; Retrofit measures under ECO4 and GBIS, Statement by Martin McCluskey on 13 October 2025 23