RdSAP 10: the biggest EPC change in 13 years
The largest update to Energy Performance Certificates since 2012 — here's what's changing and what it means for your property.
What is RdSAP 10?
RdSAP 10 (Reduced data Standard Assessment Procedure version 10) is the new methodology for calculating EPC ratings on domestic properties.
This is the most significant update since RdSAP 9.93 was introduced in 2012. It brings substantial changes to how properties are assessed and rated for energy efficiency.
Six areas getting a major upgrade
Window assessments
More detailed window specifications including frame types, glazing quality and installation methods. Triple glazing now gets enhanced recognition.
- Improved glazing categorisation
- Better credit for modern window tech
- More accurate U-value calculations
Building envelope
Enhanced assessment of insulation, thermal bridging and air tightness. More detail on wall construction and roof insulation.
- Updated U-value standards
- Improved insulation recognition
- Better thermal-bridge calculations
Heating systems
Updated efficiency ratings for modern heating systems including heat pumps, hybrids and smart controls.
- Better recognition of heat pumps
- Updated boiler efficiency ratings
- Enhanced smart-control credits
Renewable energy
Improved calculations for solar PV, solar thermal and battery storage with more accurate generation estimates.
- Better solar generation modelling
- Battery storage recognition
- Updated renewable energy factors
Ventilation
More comprehensive assessment of ventilation, including mechanical ventilation with heat recovery (MVHR).
- MVHR system recognition
- Improved ventilation credits
- Better air-quality considerations
Lighting
Updated assumptions reflecting LED adoption and smart lighting controls in modern properties.
- LED standard assumptions
- Smart lighting recognition
- Updated consumption models
How will it affect your property's rating?
Properties likely to see improved ratings
- Modern triple-glazed windows
- Heat pumps or hybrid heating systems
- Solar PV and battery storage
- Well-insulated modern builds
- MVHR systems
- Smart heating controls
Properties that may see lower ratings
- Older properties with single glazing
- Less efficient boilers
- Poor insulation
- High thermal bridging
- Older electric storage heaters
The changes are designed to better reflect real-world energy consumption and give more credit to modern, efficient technologies. Many properties will see their ratings change compared to the old methodology.
What you need to know
Existing EPCs remain valid
Issued before 15 June 2025? It's valid for the full 10-year term. You don't need a new one until it expires.
New assessments use RdSAP 10
All EPCs from 15 June 2025 use the new methodology. There's no choice to use the old system.
Slightly longer on site
Due to the extra detail required, RdSAP 10 assessments may take a bit longer than the old methodology.
More accurate ratings
The new system better reflects actual energy performance and running costs.
Updated recommendations
Improvement suggestions will be more tailored to modern energy efficiency measures.
No price increase
Despite the additional complexity, our EPC price stays at £60.
RdSAP 10 milestones
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Now → 14 June 2025
RdSAP 9.93 — the current methodology, in place since 2012.
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15 June 2025
RdSAP 10 becomes mandatory for all domestic EPCs in England and Wales.
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From 15 June onwards
All new EPCs use RdSAP 10. Older EPCs remain valid until expiry.
Three steps to prepare your property
1. Gather documentation
Have ready any certificates or receipts for:
- Window installations and glazing specs
- Boiler service records and efficiency ratings
- Insulation installation certificates
- Solar PV installation documents
- Heat pump specifications
2. Consider upgrades
To make the most of RdSAP 10:
- Upgrade to an A-rated condensing boiler
- Install or top up loft insulation
- Add smart heating controls
- Upgrade to double or triple glazing
- Install solar PV
3. Time it right
Quick guidance on when to book:
- If selling soon, a current EPC may be enough
- Planning improvements? Wait until they're done
- New EPCs from 15 June 2025 are valid for 10 years
- Allow time for upgrades to bed in
Need an EPC under the new RdSAP 10 system?
Our assessors are fully trained on the new methodology and ready to go.
Have a question? Need a quote?
Drop us a message and we'll come back to you fast — usually within the same working day.
- Phone 01634 944203
- Email hello@edjservices.co.uk
- Area Kent & South East London
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Hours
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Sat 9:00–13:00
Sun closed