RdSAP 10 Changes: What Landlords Need to Know
The new EPC assessment methodology is now in use. Here is how it works, what has changed, and whether you should wait to get your property assessed.
RdSAP 10 Status
Launched June 2025
RdSAP 10 is now the standard methodology for all new EPC assessments. If you get a new EPC today, it will be calculated using RdSAP 10. Existing EPCs calculated under RdSAP 9 remain valid until their expiry date (10 years from assessment).
The Reduced Data Standard Assessment Procedure (RdSAP) is the methodology used to calculate EPC ratings for existing dwellings in England and Wales. RdSAP 10 represents the most significant update to this methodology in over a decade, bringing changes that affect how properties are rated and which improvements are recommended.
For landlords, understanding RdSAP 10 is important because your property might receive a different rating under the new methodology compared to the old one. This could affect your compliance strategy for the 2030 deadline.
What is RdSAP?
RdSAP (Reduced Data Standard Assessment Procedure) is a simplified version of the full SAP (Standard Assessment Procedure) used to calculate energy performance for existing homes. While SAP is used for new builds where detailed specifications are known, RdSAP uses standardised assumptions to assess existing properties based on observable characteristics.
An EPC assessor visits the property, records observable features (wall construction, insulation presence, heating system, glazing, etc.), and inputs this data into RdSAP software. The software then calculates the energy efficiency score and rating.
Previous methodology (until June 2025)
Current methodology (from June 2025)
Full methodology for new builds
Key Changes in RdSAP 10
RdSAP 10 introduces several significant changes to how properties are assessed and scored. The most impactful relate to carbon emission factors and how different technologies are valued.
Updated Carbon Emission Factors
The electricity grid has become significantly cleaner since the previous factors were set. RdSAP 10 uses updated emission factors that reflect this decarbonisation.
Revised Default Assumptions
Default assumptions for older properties have been updated. This affects how properties are scored when specific details are unknown or unobservable.
Changed Improvement Valuations
The relative value of different improvements has changed. Some measures may contribute more or fewer EPC points than before.
New Data Collection Requirements
Assessors may need to record additional data points or provide more evidence for certain features. This improves accuracy but may require more thorough inspections.
How Ratings May Change
The same property assessed under RdSAP 9 and RdSAP 10 may receive different scores. The direction and magnitude of change depends on the property's characteristics, particularly its heating system.
Comparison of property ratings under RdSAP 9 versus RdSAP 10
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Likely to Score Better
- Properties with heat pumps (air or ground source)
- All-electric properties with modern storage heaters
- Properties with solar PV installations
- Properties with solar thermal hot water
- Electric vehicle charger presence (minor benefit)
May Score Similar or Slightly Lower
- Properties with gas boilers (relative decline vs electric)
- Properties with oil heating
- Older properties where assumptions have changed
- Properties where previous assessment was generous
Impact by Property Type
Different property types will experience RdSAP 10 differently, depending on their typical heating systems and construction characteristics.
Victorian and Edwardian Properties
Impact varies significantly by heating type. If you have switched to a heat pump, expect improved scores. If still on gas, scores may be similar or slightly lower. Updated default assumptions for solid walls may affect properties where insulation status is uncertain.
1930s Semi-Detached
Typically gas-heated with cavity walls. Expect broadly similar scores under RdSAP 10 unless you have installed renewable technology. Cavity wall insulation continues to be highly valued. If your property was borderline C, consider a new assessment to check your position.
Purpose-Built Flats
Modern purpose-built flats often already score well. If your flat uses electric heating (common in newer builds), you may see improved scores. Communal heating systems are assessed differently; results depend on the specific system type.
Rural Properties (Oil Heated)
Oil-heated properties may see relative score declines as oil carbon factors remain high while electricity factors improve. Consider this when planning improvements; switching away from oil provides greater EPC benefit under RdSAP 10 than it did under RdSAP 9.
Should You Wait or Act Now?
A common question from landlords has been whether to wait for RdSAP 10 before getting a new EPC or making improvements. Now that RdSAP 10 is in use, the question is simpler: any new EPC you get will use RdSAP 10.
Get a New EPC Now If...
- Your current EPC is more than 5 years old and you have made improvements
- You have installed electric or renewable heating since your last EPC
- You are borderline D/C and think RdSAP 10 might help your rating
- You need an accurate baseline for planning improvements
- Your EPC will expire before 2030 anyway
Keep Your Current EPC If...
- Your current EPC shows C or above and is still valid
- You have not made any changes since your last assessment
- You have a gas boiler and suspect RdSAP 10 might lower your score
- Your EPC does not expire until after 2030
Practical Advice for Landlords
Here is how to approach RdSAP 10 pragmatically:
Check Your Current EPC Expiry
If your EPC expires before October 2030, you will need a new one anyway. Plan when to get this done based on your improvement timeline.
Understand Your Heating System
The biggest variable in RdSAP 10 impacts is heating type. Electric and renewable heating properties benefit; gas and oil see relative decline. Know where you stand.
Review Old Improvement Recommendations
Improvement recommendations on EPCs calculated under RdSAP 9 may be less accurate under RdSAP 10. If planning major improvements, consider getting a fresh assessment first.
Document All Improvements
Keep records of all energy efficiency improvements. When getting a new EPC, provide this documentation to the assessor to ensure improvements are correctly recorded.
Consider the Long-Term Direction
The methodology changes reflect grid decarbonisation. This trend will continue. Investing in electric or renewable heating positions your property well for future methodology updates.
Plan Your Improvements
Use our calculator to estimate costs and see what improvements make sense for your property.
Related Guides
EPC C 2030 Deadline
Everything you need to know about the October 2030 compliance deadline.
MEES Regulations Guide
Complete guide to Minimum Energy Efficiency Standards and how they apply.