The way your home's energy performance is measured is changing. The familiar single A–G EPC rating is being replaced by four separate metrics (Fabric Performance, Heating System, Smart Readiness, and Energy Cost) calculated using the Home Energy Model (HEM) instead of SAP/RdSAP. The new EPCs are now expected to launch in the second half of 2027 (delayed from the original October 2026 target). From launch, HEM replaces SAP and RdSAP, and new certificates carry a legacy version of the A–G rating until at least the end of 2029. Your existing EPC remains valid for 10 years.
What Is Changing?
From One Rating to Four Metrics
The current EPC gives you a single A–G rating based primarily on energy cost. This hides important detail. For example, a home with excellent insulation but an old gas boiler might get the same overall rating as a home with poor insulation and a slightly newer boiler. The new system separates these into four distinct metrics:
| New Metric | What It Shows | Current EPC Equivalent |
|---|---|---|
| Fabric Performance (A–G) | Building envelope quality: walls, roof, floor, windows | Hidden within the overall rating |
| Heating System (A–G) | Heating efficiency and carbon intensity | Partially reflected in overall rating |
| Smart Readiness (A–G) | Smart controls, battery storage, grid interaction | Not measured at all |
| Energy Cost (£/year) | Estimated annual energy running costs | Roughly equivalent to the current rating basis |
For a full explanation of each metric, see our New EPC Metrics Explained page.
More Accurate Assessment
The current EPC calculation (RdSAP) uses monthly averages and struggles to model modern technologies accurately. The new HEM-based calculation uses half-hourly simulation, which means:
- Heat pumps are properly credited, as their efficiency varies with outdoor temperature, which HEM captures at every timestep
- Solar PV is modelled more accurately. HEM tracks how much electricity you use on-site versus exporting to the grid
- Battery storage is modelled dynamically, with half-hourly charge and discharge, rather than the simple allowance RdSAP 10 makes today
- Smart controls get a dedicated metric, currently ignored in EPC assessments
The Engine Behind It: RdSAP Becomes HEM
Today, the EPC for an existing home is produced by RdSAP (Reduced Data SAP), a stripped-down version of the calculation that fills in unknowns with age-based assumptions. The reform replaces RdSAP with a reduced-data form of the Home Energy Model: the assessor records what they can see and the model fills the gaps, but the underlying engine is the same accurate, half-hourly HEM used for new homes. RdSAP 10 (the current version, in use since 15 June 2025) stays live until the switch, which is targeted for the second half of 2027. For the detail, see our RdSAP to HEM transition guide.
Impact on Property Values
The new EPC system will gradually influence how the market perceives different properties:
Properties with Gas or Oil Heating
Under government proposals, fossil fuel heating (gas, oil, LPG) would not achieve a C rating on the Heating System metric. Over time, as the new EPC format becomes familiar to buyers and estate agents, properties with low Heating System ratings may face downward pressure on valuations. This is a gradual market shift, not an overnight change.
Properties with Good Insulation
If you have invested in insulation, the separate Fabric Performance metric will make this visible for the first time. Under the current system, good fabric can be masked by a poor heating rating (and vice versa). The new system separates these, potentially improving the perceived value of well-insulated homes.
Properties with Smart Technology
Homes with solar PV, battery storage, smart heating controls, and EV charging will score well on the Smart Readiness metric. This is entirely new. Current EPCs give little or no credit for these technologies. As the market increasingly values energy flexibility and self-sufficiency, this metric could become a selling point.
What Should You Do?
If You Are Not Selling or Letting
Nothing. Your existing EPC remains valid. The changes only affect you when you next need an EPC. In the meantime, any energy improvements you make will be better recognised when you do eventually get a new assessment.
If You Are Selling or Letting Soon
- If your current EPC is still valid (less than 10 years old), you can continue to use it
- If you need a new EPC after the new system launches (expected H2 2027), it will be in the new four-metric format
- During the transition (H2 2027 until at least the end of 2029), new EPCs will show both the legacy A–G rating and the new four metrics
If You Are Planning Energy Improvements
The new system changes which improvements have the most impact on your EPC. Here are the most effective upgrades under the four-metric framework:
| Improvement | Metric Improved | Typical Impact |
|---|---|---|
| Wall / loft / floor insulation | Fabric Performance | Could improve rating by 1–3 bands |
| Heat pump installation | Heating System | From D/E (gas boiler) to A/B |
| Solar PV | Energy Cost + Smart Readiness | Significant reduction in estimated annual costs |
| Battery storage | Smart Readiness + Energy Cost | Improves both (dynamically modelled, not the simple RdSAP 10 allowance) |
| Smart heating controls | Smart Readiness | Contributes to Smart Readiness rating |
| Double to triple glazing | Fabric Performance | Moderate improvement to fabric rating |
If you are considering a heat pump, the Boiler Upgrade Scheme offers £7,500 towards air-to-water and ground source systems. From April 2026 it also covers air-to-air heat pumps at £2,500, and a £2,500 grant for heat batteries has been announced. Planning rules have also been relaxed: the one-metre boundary rule has been removed, and air-to-air systems now count as permitted development.
When Does This Happen?
| Date | What Happens |
|---|---|
| January – March 2026 | HEM: EPC consultation (closed 18 March 2026) |
| H2 2027 (confirmed delay) | New HEM-based EPCs launch; HEM replaces SAP and RdSAP |
| H2 2027 – end of 2029 (at least) | New EPCs carry a legacy A–G rating alongside the four metrics; older certificates stay valid until they expire |
| After the end of 2029 (earliest) | Legacy A–G rating removed from new EPCs |
The government confirmed in March 2026 that the EPC reform launch has been delayed from October 2026 to the second half of 2027. A specific date will be confirmed by summer 2026. See our Timeline & Status page for live updates.
Frequently Asked Questions
When do I need to get a new-format EPC?
Only when selling, letting, or when your current EPC expires (10 years from issue). You do not need to get one just because the system is changing. From the second half of 2027 (delayed from the original October 2026 target), new HEM-based EPCs launch carrying a legacy version of the A–G rating until at least the end of 2029, while older certificates stay valid for the rest of their ten-year life. Separately, the government plans to tighten when an EPC is required: at the point of marketing (removing the 28-day grace), for a whole HMO when even one room is let, and for short-term and holiday lets regardless of who pays the bills.
Could my EPC rating go down under the new system?
The new system uses four separate metrics, so there is no direct comparison to the old single rating. Some aspects may score better (insulation is more accurately recognised), while others may score worse (fossil fuel heating scores poorly on the Heating System metric). Overall, HEM gives a more honest reflection of your home's actual performance.
Should I improve my home before selling to get a better EPC?
It depends on your property. Under the new system, the most impactful improvements are: insulation (improves Fabric Performance), heat pump (improves Heating System from D/E to A/B), smart controls and battery storage (improves Smart Readiness), and solar PV (reduces Energy Cost). The separate metrics let you target the specific area where your property scores poorly.
How will MEES work with the new EPC metrics?
The January 2026 government response confirmed the equivalent of EPC C by 1 October 2030 for the domestic private rented sector. The standard is fabric-first: meet the Fabric Performance standard, then either Heating System or Smart Readiness. There is a £10,000 cost cap and penalties up to £30,000 per breach. Because a gas boiler would cap at Band D on Heating System under the proposed banding, solar PV plus a smart meter can meet the second limb via Smart Readiness without a heat pump. The metric bands are not yet finalised and the uplift needs a new Act of Parliament that has not passed.
Will a new-format EPC cost more?
Pricing has not been confirmed. HEM assessments require more detailed data collection, which may affect assessment costs. The fee model for ECaaS has not been settled either: MHCLG is still working with the accreditation schemes on how fees will be applied, and the schemes will keep their own commercial front-end software. It is too early to say whether the overall cost will change.
Related Pages
HEM & FHS for Homeowners
Overview of what HEM and the Future Homes Standard mean for homeowners.
New EPC Metrics Explained
Full breakdown of all four new EPC headline metrics.
EPCs & HEM
Complete guide to how EPCs are changing under HEM.
RdSAP to HEM Transition
How existing-home EPCs move from RdSAP to the Home Energy Model.
HEM and Your Home
Plain English guide to what HEM means for your home and bills.