England and Wales · Last checked against GOV.UK and BRE: 31 October 2026

The June 2025 EPC method change (RdSAP 10): is your old EPC still right?

Key points

• The method changed on 15 June 2025. From that date, the government's approved method for rating existing homes in England and Wales is the RdSAP10 edition of the Standard Assessment Procedure.
• An older EPC isn't cancelled by the change. GOV.UK says an EPC is valid for 10 years, or until a newer EPC is produced for the same building. None of the GOV.UK pages we checked says the method change cut short the validity of certificates lodged earlier.
• Current scores look about the same; potential scores don't. Evolving Home analysed the England & Wales EPC register. The typical (median) current SAP score was 70 before the switch and 71 after it. The typical gap between a certificate's current and potential score fell from 13 points to 7.
• Many homes have an old certificate. For 31% of properties in the register, the newest certificate is 10 or more years old.

What changed on 15 June 2025?

An EPC rates a home's energy efficiency from A (best) to G (worst). Behind that letter is the government's Standard Assessment Procedure (SAP). SAP was developed by the Building Research Establishment (BRE) and is used to generate EPCs for all homes. Existing homes are assessed with a reduced-data version called RdSAP. It was introduced in 2005 and fills gaps with a set of assumptions about the home, so the assessor collects less data.

A government notice of approval says the new methodology "takes effect on 15 June 2025". For existing dwellings in England and Wales, the approved method is the "RdSAP10 edition". BRE, which maintains the specification, published RdSAP 10 conventions marked "Applicable from 15 June 2025". The GOV.UK SAP page currently lists RdSAP 10.0.1 as the current version.

BRE's RdSAP 10 specification lists the significant changes from the previous version (RdSAP 2012). They include:

• Windows: window measurements are required for all windows, and the table of window U-values is expanded.
• Walls: brick-wall U-values are revised to account for wall thickness, and stone-wall U-values are revised.
• Roofs and floors: roof insulation has more options, floor insulation is revised and heated basements are added.
• Construction age: a new age band is added and all U-value tables are updated.
• Hot water: hot water tank size and insulation are now included.
• Solar: PV batteries and PV diverters are added.
• Heat pumps: heat pumps are calculated as in full SAP 10.2.
• Prices and metrics: RdSAP 10 has its own fuel prices and metrics.

Some changes affect how a home is recorded:

• Windows are measured one by one. The specification requires window measurements "for all windows".
• Flats are recorded differently. For flats and maisonettes, "detachment does not need to be recorded" where internal dimensions are used.
• Solar panels and export. The assessor now records whether the home is "export-capable". BRE says the savings from generated electricity depend "on whether it is used directly within the dwelling or exported".

The specification also changed the table of improvement measures used to build a certificate's recommendations.

• Improved U-values were revised for all building elements.
• The measure to insulate a party wall was removed.
• Air and ground source heat pumps are "not alternative measures anymore".
• PV battery and PV diverter measures were added.

A measure is recommended only if it raises the SAP rating by at least 1 point. (For cylinder insulation, draughtproofing and low-energy lighting, the threshold is 0.5 points.) The specification adds that these thresholds "may be overridden by amended values in the PCDB" (the Product Characteristics Database).

Is my old EPC still right?

There are two separate questions here.

1. Is it still valid? GOV.UK says an EPC "is valid for 10 years". Its EPC guide adds that a certificate stays valid for 10 years "or until a newer EPC is produced for the same building", and that "only the most recent EPC for each distinct building or building unit is valid". If your property has no EPC, or its EPC has expired, you need a new one before you sell or rent it. You can check what is on record, and download a copy for free, with GOV.UK's Find an energy certificate service.

2. Does it still describe your home well? That's a separate question. An EPC is a snapshot taken on the day of the assessment, using the method in force then. If you have insulated, changed your heating or added solar since then, the certificate won't show it. GOV.UK also notes that an assessor can't include features they can't see, such as cavity wall insulation, unless you have supporting evidence such as receipts. And since 15 June 2025, any new certificate is calculated with RdSAP 10, not the method your older certificate used.

So an older certificate can be fully valid and still differ from what a new assessment would show today.

Why does a new EPC show less improvement potential?

Every EPC shows two ratings: the current rating and a potential rating. GOV.UK explains that the potential rating "is based on all cost-effective recommendations being implemented". When the method behind those recommendations changes, the potential rating can change even if the home hasn't.

That is the pattern we see in the public register. We looked at certificates for existing homes lodged each month from January 2024 to October 2026.

Grouping certificates into the period before the switch (Jan 2024 – May 2025) and the period after it (July 2025 onwards) gives these figures:

• the typical current score was 70 before and 71 after, and
• the typical gap between current and potential fell from 13 points to 7.

The narrower gap shows up across many kinds of home. For homes built before 1900 it went from 20 points to 12, for houses from 15 to 8, and for bungalows from 18 to 9.

The recommendations changed at the same time. Comparing existing-home certificates lodged in January–May 2025 with July–December 2025:

• "Solar water heating" was recommended on 65.1% of certificates before and 3.8% after;
• the average number of recommendations per certificate fell from 3.2 to 2.4; and
• air or ground source heat pump recommendations went from almost none to 0.5% of certificates.

Party wall insulation was recommended on 3.6% of certificates lodged in January–May 2025. It doesn't appear on any certificate lodged since July 2025, in line with the measure being removed from the specification.

A cross-check on current ratings. The Scottish Government modelled the same Scottish homes under the old and new methods. It found the share rated C or better barely moved, from 53.87% to 54.03%. That study covers Scotland's housing stock, not England and Wales, and it says nothing about potential ratings. It is consistent with what the register shows for current ratings.

The 1-point rule above applies under RdSAP 10. On its own, though, it doesn't explain why solar water heating dropped out of so many recommendations.

What we can and can't say.

• Correlation, not proof. The timing lines up closely with 15 June 2025, and the official specification did change the improvement measures. But our analysis shows a correlation in time. It doesn't prove which part of the method caused which change, and we haven't found an independent published study of the drop.
• Different homes. The before and after groups are the certificates lodged in each period, not the same homes reassessed. A certificate is lodged when a home is sold, let or reassessed, so homes that change hands often are over-represented.

What's clear is that potential scores on certificates from before and after June 2025 were not calculated the same way. Comparing a pre-June-2025 potential score with a newer one tells you about the change of method as much as about the home.

What this means for you

If you own your home. You don't need a new EPC just because the method changed. You need one when you sell or rent out, if you don't already have a valid one. If you're planning improvements, treat the "potential" figure on an older certificate with care. A new RdSAP 10 assessment may show a smaller gap, and a different list of recommended measures.

If you're a small landlord. The law in force today, per GOV.UK, is that since 1 April 2020 landlords can't let, or continue to let, a property covered by the domestic Minimum Energy Efficiency Standard (MEES) Regulations if its EPC rating is below E, unless a valid exemption is in place. Local authorities enforce this and can issue penalties.

Separately, the government has said it aims for as many privately rented homes as possible to reach EPC Band C "or equivalent" by 2030. It says it is "exploring policy design options following the 2026 consultation". That is a stated aim, not a rule in force. Check GOV.UK for the current position before acting on it.

Comparing certificates. Before comparing any two certificates, check each one's lodgement date. If one predates 15 June 2025 and the other doesn't, they were calculated with different methods.

If you think a certificate is wrong. GOV.UK says to contact the energy assessor first, then their accreditation scheme. Where information is found to be incorrect, a new EPC must be issued.

Looking further ahead. GOV.UK says a new Home Energy Model will replace SAP for rating homes. The government consulted on Home Energy Model EPCs from 21 January to 18 March 2026. Nothing about it changes how your current certificate is valid today.

Where the Evolving Home Health Score fits

The Evolving Home Health Score is a free, indicative planning aid for homes in England and Wales. It is not an EPC. It can't replace a certificate from an accredited assessor, and it can't be used where the law requires an EPC. It can help you see where your home stands and what to look into next. Facts you confirm about your home can update your Health Score, and every change is labelled owner-confirmed.

Get your free Health Score →

FAQ

About the figures

Figures marked as register data are Evolving Home analysis of the England & Wales EPC register (OGL v3.0). They are indicative and are not endorsed by MHCLG.

• What was analysed. The domestic EPC bulk file for England and Wales, extract dated 13 October 2026, covering certificates lodged up to 12 October 2026.
• Certificates, not homes. Figures count certificates, not homes, except the "newest certificate per property" figure, which uses the register's property reference (UPRN).
• Before vs after. "Before" is January 2024 – May 2025. "After" is July 2025 – October 2026. June 2025 is excluded as the switch month.
• Gap. The gap is potential SAP minus current SAP for each certificate.
• No individual data. No address or individual certificate is published.

Sources

• GOV.UK: Methodologies for expressing the energy performance of buildings in England and Wales: notice of approval (15 June 2025)
• GOV.UK: Standard Assessment Procedure
• GOV.UK: Energy Performance Certificates
• GOV.UK: A guide to Energy Performance Certificates for the marketing, sale and let of dwellings
• GOV.UK: Domestic private rented property: minimum energy efficiency standard – landlord guidance
• GOV.UK: Find an energy certificate
• BRE: RdSAP 10 Specification (June 2025)
• BRE: RdSAP 10 Conventions v12
• Scottish Government: Energy Performance of Buildings (Scotland) Regulations 2025: stock model research, section 5
• legislation.gov.uk: Impact Assessment, ECO SAP10/RdSAP10 update (DESNZ)

This guide is general information for England and Wales, not legal or financial advice.