The current A to G EPC system is being replaced by the Home Energy Model in the second half of 2027. This guide explains what the four new metrics mean for your property, why gas heating becomes a liability under the new rules, and what funded options are available to act now.
If you own a home or a rental property in England or Wales, a significant change is coming to the way your property is assessed for energy efficiency. The current Energy Performance Certificate system, which has rated homes on a simple A to G scale since 2007, is being replaced.
The replacement is called the Home Energy Model. It is a fundamentally different way of measuring how energy efficient a property is, and for millions of homeowners and landlords, it will change the rating their property holds overnight.
The Government has confirmed that the Home Energy Model will roll out in the second half of 2027. That gives property owners time to prepare. But the window to act using the funded schemes available right now is closing. Understanding what the Home Energy Model is and what it means for your property is no longer something you can defer.
What Is the Home Energy Model?
The Home Energy Model, commonly referred to as HEM, is the new methodology that will replace the Standard Assessment Procedure (SAP) used to produce the current generation of Energy Performance Certificates. SAP has been in use since 2007. It is widely regarded as outdated, crude, and poor at capturing the real energy performance of modern homes or the impact of low-carbon heating systems.
The Home Energy Model was developed by the Department for Energy Security and Net Zero. It is designed to give a more accurate, detailed, and future-proof picture of how a property performs. Where SAP produces a single A to G rating, the Home Energy Model will produce four separate metric scores for every property assessed.
The Four Metrics Explained
Rather than producing a single A to G rating, the Home Energy Model will assess a property across four separate metrics. Each metric will receive its own rating, giving a much more detailed and honest picture of how a property performs.
1. Energy Cost
This measures how much it costs to run the property on its current energy sources, calculated using current and projected fuel prices. Unlike SAP, which uses fixed historical prices, the Home Energy Model will use more dynamic cost modelling.
2. Carbon Emissions
This measures the carbon footprint of the property based on how it is heated and powered. Properties running on renewable electricity will perform very differently from those relying on gas, even if their fabric is identical.
3. Energy Use Intensity
This measures how much energy the property consumes per square metre. It is a more useful measure of fabric efficiency and is less distorted by fuel type than the current cost-based calculation.
4. Heating System Metric
This is the most significant change from the current system. The Home Energy Model will score your heating system independently from the fabric of the building. Gas boilers, oil boilers, and other fossil fuel heating systems will score poorly on this metric regardless of how well insulated the property is. This is the metric that will catch millions of landlords and homeowners off guard.
Why the Heating System Metric Changes Everything
Under the current SAP methodology, it is possible to achieve an EPC Band C rating while running the property on a gas boiler. Many landlords have done exactly this by investing in insulation, double glazing, and other fabric improvements. Under the Home Energy Model, that approach will not work.
Fossil fuel heating systems cannot achieve a C rating on the Heating System metric under the Home Energy Model. This means that landlords who currently hold an EPC Band C certificate based on insulation improvements may find their property falls short of compliance requirements when their certificate comes up for renewal under the new methodology.
The MEES regulations require all privately rented properties in England and Wales to meet minimum energy efficiency standards. The current target of EPC Band C by October 2030 remains in place. What the Home Energy Model changes is how that Band C is defined and measured. A rating that looks like a C today may not survive the transition to the new four-metric system.
When Does the Home Energy Model Come Into Effect?
The Government has confirmed that the Home Energy Model will replace SAP in the second half of 2027. This is later than originally planned. The initial timeline pointed to October 2026, but the rollout has been pushed back to allow for further consultation and industry preparation.
Current EPC certificates remain valid for ten years from the date of issue, so many properties will not require a new assessment until well after 2027. But when they do, the assessment will be conducted under the Home Energy Model rather than the current SAP methodology.
The delay to 2027 does not change the October 2030 MEES compliance deadline. Landlords still need to reach Band C by then. The delay simply means there is more time to understand the new rules before the new measurement system is in place.
Which Properties Are Most Affected?
The properties most significantly affected by the Home Energy Model are those that currently rely on gas central heating and have been rated on the strength of their insulation rather than their heating system.
These are typically properties built before 1990, which make up the majority of the housing stock and the majority of gas heated homes. Mid-terrace and semi-detached houses that have solid walls or cavity walls with incomplete or absent insulation, where the current EPC has compensated with a modern boiler. Properties that achieved EPC Band C or D through fabric improvements alone, without addressing the heating system. Buy to let properties where the landlord has invested in insulation upgrades to meet MEES requirements but retained the existing gas central heating system.
What Funded Support Is Available Right Now?
The good news is that significant funding is available right now to help homeowners and landlords address the measures that the Home Energy Model will reward most heavily. Acting now, before 2027, means you can use existing funding to get ahead of the new system.
The Warm Homes Plan
The Warm Homes Plan provides up to £30,000 of fully funded improvements for households with an income under £36,000 or in the most deprived postcodes (IMD deciles 1 and 2), with an EPC rating of D to G. There is no loan and no repayment. Funded measures include insulation, heat pumps, solar panels, battery storage, and smart controls.
The Warm Homes Local Grant
Delivered through local authorities and running to March 2028, the Warm Homes Local Grant targets households in fuel poverty or at risk of fuel poverty. Eligibility and available measures vary by local authority area, but the scheme covers insulation, heating upgrades, and low-carbon technology. Contact your local council or a qualified energy advisor to check eligibility in your area.
The Boiler Upgrade Scheme
The Boiler Upgrade Scheme provides £7,500 towards an air source heat pump with no income test. The grant is deducted from your installer quote before you pay, so there are no upfront grant applications to manage. A heat pump will score well on the Heating System metric under the Home Energy Model, making it one of the most effective investments you can make for future EPC compliance.
What a C Rating Will Really Mean After 2027
Current EPC certificates issued under the SAP methodology will not automatically provide protection under the Home Energy Model. A certificate that shows Band C today may not reflect a strong rating under the four-metric HEM assessment. The only way to know how your property will perform under the new system is to have it assessed or to take the steps needed to perform strongly across all four metrics.
The most important step is the same regardless of timeline: address the heating system. A property with excellent insulation and a gas boiler will struggle under the Home Energy Model. A property with good insulation and a heat pump will perform strongly across all four metrics.
How Cucumber Eco Can Help
At Cucumber Eco, we provide free energy consultancy to homeowners and landlords who want to understand what the Home Energy Model means for their property and what funded options are available to them right now. Our consultants are qualified and independent. We assess your property, identify the measures that will have the greatest impact on your EPC rating under both the current and incoming methodology, and guide you through the funded routes available.
There are funded routes available right now that can address the heating system, insulation, and renewable energy measures that will matter most under the Home Energy Model. The time to access them is before 2027, while the funding is available and the competition for installations is lower. Get in touch with our team at cucumbereco.co.uk to book a free consultation.