The UK is transitioning to the Home Energy Model (HEM), a major shift for the entire property sector. While the official EPC reform has been delayed to the second half of 2027, Cotality is using its expertise in surveying technology and data analytics to ensure this new system is implemented successfully and remains reliable for all stakeholders.
The transition to using the Home Energy Model (HEM) to assess energy performance is a significant change for homeowners, landlords, the property market and the energy assessment supply chain alike.
This week the government has announced that the related EPC reform will be launched in the second half of 2027 rather than October 2026, and next week it’s latest consultation on the Home Energy Model comes to an end.
At Cotality, we are at the forefront of this transition. Through our comprehensive property services - spanning mobile surveying technology, data analytics, and quality assurance via ECMK - we understand the application of the model through the full property ecosystem, and what will drive (or undermine) success.
For stakeholders preparing their consultation responses, we have distilled our position on the core metrics and structural changes. Our objective is clear: to ensure the next generation of Energy Performance Certificates (EPCs) remain affordable, repeatable, and transparent.
The structural challenge: The risks of a "two-tier" market
The government has proposed a modular approach to data input, allowing assessors to enter measured data where available or rely on defaults. While offering more granularity, Cotality is concerned this may not deliver accuracy or consistency.
Without a rigorous framework for verifying data capture and reported results, we risk creating a "two-tier" market. Homeowners may face confusion over different assessment costs, and the resulting EPCs could lack comparability. Assessors may not wish to invest in the training and equipment required to capture alternative inputs without clear market demand.
Our Position: Alternative inputs are welcome where data is drawn cost-effectively from trusted, government-backed sources (such as MCS or Building Control) via API as a standard, rather than an option. This reduces the administrative burden on assessors while ensuring data integrity. Specific consideration needs to be given to any additional alternative inputs to be captured on-site as each will require a verified and auditable process.
Redefining metrics: Physics vs. complexity
We have evaluated the proposals for the four new primary metrics for the EPC. Our stance is rooted in building physics, assessor needs and consumer clarity.
1. Fabric Energy Efficiency (FEE): The gold standard
Cotality strongly agrees with utilising FEE (kWh/m²/year) as the primary metric. It provides a robust, physics-based signal regarding the intrinsic quality of the building envelope. We also recommend replacing broad assumptions for fittings like fans and showers with actual onsite data which is easy to verify and audit where applicable.
2. Heating systems: Simplicity over presumption
We disagree with the proposed Heating System metric. The current proposal is overly complex and lacks transparency.
A rating based simply on carbon emissions would be far easier for homebuyers and renters to understand at a glance, and clearly linked to targets for reducing reliance on fossil fuels – relevant to both energy security and decarbonisation goals.
3. Cooking appliances: A strategic misstep
Cotality strongly disagrees with including cooking appliances in the EPC. Cooking accounts for a small fraction of domestic energy, homeowners who have invested in heat pumps should not be penalised because they have not yet refurbished their kitchen and in social housing, hobs are often tenant-owned, making it inappropriate for inclusion in a metric that in turn through Minimum Energy Efficiency Standards places responsibility on landlords. The future of gas hobs is better determined through product policy and the impact of gas standing charges as the market evolves.
4. Smart readiness and cost
While we support recognising grid flexibility, it is challenging to explain to the public. Even more so in the case of the Smart Readiness metric which currently conflates onsite generation with peak demand reduction.
Furthermore, we disagree with presenting Costs in pounds (£). Given that an EPC is valid for 10 years, monetary figures date quickly; banding is our preferred way to ensure long-term comparability, or apply dynamic updates to financial figures as Cotality does in its online tools for landlords and homeowners.
5. Naming, and why it matters
We encourage all stakeholders to demand simple, plain-language terminology and support the name HEMEX (HEM for Existing Dwellings), or HEM:EPC which more succinctly communicates the Model in use and its application to the EPC.
We do not think it needs to reference use of modular inputs, as there may be multiple approaches, each needs consideration on its own terms, and the approaches may change over time.
Perhaps most important is to move on from the use of ‘Reduced’ in the terminology. Too often the ‘Reduced’ nature of RdSAP is seen to make it less valuable than SAP, but it offers a considerable advantage over the current SAP approach by capturing important aspects of the fabric without which it would be impossible to model options for improvement.
While the EPC may provide a quick indication of where a home is now, what matters most to the landlords and homeowners we work with is what should they do next – and we look forward to the confirmation of the metrics.
In conclusion
Ultimately, Cotality believes that for the Home Energy Model to succeed, the resulting EPC system must remain affordable, repeatable, and transparent. By prioritising a data-led approach that utilises verified, government-backed sources, the industry can avoid the risks of a fragmented "two-tier" market and ensure that assessments provide a reliable basis for decision-making in the property market. Whatever decisions are made, we remain committed to leveraging our technological and quality assurance expertise to guide stakeholders through this transition toward a decarbonised and resilient building stock.
