2027 EPC Changes: What the Home Energy Model Means for You
Discover how the 2027 Home Energy Model (HEM) replaces the single A–G EPC score and SAP. Find out what changing metrics mean for your property and book with Veridian Energy today.
Dave Cawood
9/23/20263 min read
The End of the Single A–G Rating: What the New Home Energy Model Means for Your EPC
If you own a home, manage rental properties, or plan to buy in the near future, you are likely familiar with the traditional Energy Performance Certificate (EPC). For over two decades, EPCs have boiled a property's efficiency down to a single A–G color-coded band.
That system is set for its biggest overhaul yet.
In the second half of 2027, the UK government will officially scrap the old Standard Assessment Procedure (SAP) framework and replace it with a dynamic, physics-based simulation engine known as the Home Energy Model (HEM).
Here is what is changing, why the old system is being replaced, and what it means for homeowners and landlords.
Why Is SAP Being Replaced?
The current SAP system was created back in 1993. While it has been updated over time, its core calculations rely on monthly averages and simplified assumptions.
Because SAP evaluates energy use in broad chunks of time, it struggles to fairly measure modern green technologies:
Heat Pumps: SAP applies a static efficiency score across the entire year, failing to capture how heat pump performance shifts with real-world outdoor temperatures.
Solar PV & Batteries: SAP cannot accurately model a home charging a battery using solar power at midday to run appliances during peak evening hours.
Smart Controls & Tariffs: Time-of-use tariffs and smart heating controls are virtually invisible under the old rules.
The Home Energy Model (HEM) solves this by using 30-minute interval simulations across all 8,760 hours of the year. It models building physics, weather data, and grid carbon intensity in near real time, providing an accurate, modern representation of how a house uses energy.
From 1 Score to 4 New Metrics
Instead of giving your home a single overall A–G rating, new EPCs issued from H2 2027 onward will measure performance across four distinct categories:
Fabric Performance
What It Measures: Thermal efficiency of the building structure itself.
What Drives the Rating: Wall, roof, and floor insulation; window performance; airtightness.
Heating System
What It Measures: Carbon intensity and raw efficiency of heating/hot water equipment.
What Drives the Rating: Heat pumps vs. boilers (gas/fossil boilers will be hard-capped at Band D).
Smart Readiness
What It Measures: The home's ability to shift energy demand based on grid signals.
What Drives the Rating: Smart meters, battery storage, EV chargers (V2G), and flexible controls.
Energy Cost
What It Measures: Estimated annual energy bills (in £/year).
What Drives the Rating: Overall efficiency combined with energy fuel prices.
Note on the Transition: To avoid market confusion, certificates issued between the launch in 2027 and at least the end of 2029 will display a legacy A–G rating alongside these four new metrics.
What Does This Mean for You?
1. Existing Certificates Remain Valid
If you already have a valid EPC, you do not need to get a new one immediately. Existing EPCs remain valid for their full 10-year lifespan. You will only need a HEM-based assessment when your current certificate expires, or when you next sell or let the property.
2. Boiler Penalties and Heat Pump Boosts
Under HEM's updated carbon metrics, mains gas boilers can no longer achieve high ratings. Homes relying on gas, oil, or LPG boilers will see their Heating System metric hard-capped at a Band D. Conversely, low-carbon tech like air-source or ground-source heat pumps will easily achieve Band A or B.
3. A Clearer View for Buyers and Tenants
Instead of hiding a home's structural flaws behind a cheap heating fuel source, the four-metric layout separates fabric performance from equipment. A buyer will instantly see if a property has drafty, uninsulated walls—even if the landlord installed a brand-new heating system.
4. Direct Impact on Landlords (MEES Rules)
Under the Warm Homes Plan, all private rented properties in England and Wales must reach the equivalent of an EPC C by October 1, 2030. Landlords planning retrofits should start evaluating their properties through the lens of the new metrics now, ensuring insulation and heating upgrades align with the 2027+ standard.
Key Dates at a Glance
H2 2027: Official launch of the Home Energy Model and the four-metric EPC.
H2 2027 – End of 2029: Transitional period; certificates display both the four new metrics and a legacy overall A–G rating.
1 October 2030: Deadline for all private rented sector properties in England and Wales to meet the EPC C threshold.
The Takeaway
The transition to the Home Energy Model turns the EPC from a blunt cost-estimating tool into an accurate digital reflection of how a home interacts with the grid. Whether you are planning a renovation, upgrading your heating, or preparing a rental property for the 2030 standards, understanding fabric efficiency and smart readiness today will save you money and hassle tomorrow.
Book your EPC Assessment now to avoid any issues
To avoid any potential compliance issues or sudden rating drops, consider securing a new assessment now before the changes take effect. Because Energy Performance Certificates remain legally valid for 10 years, obtaining an EPC today under the existing Standard Assessment Procedure (SAP) gives you complete peace of mind—sparing you from worrying about the new Home Energy Model methodology for another decade. Book your assessment now with Veridian Energy to lock in your 10-year compliance today!
