Why EPC Ratings Matter More in 2026
The Energy Performance Certificate has become increasingly consequential for UK homeowners:
- Green mortgages: NatWest, HSBC, Barclays, and others offer preferential rates for homes rated EPC A or B. In 2026, the rate differential is typically 0.1–0.3 percentage points.
- Rental sector: The government's trajectory towards requiring EPC C for new private rental tenancies by 2028 is pushing landlords to act now.
- Property value: Research by Rightmove and RICS consistently shows EPC A/B homes command a premium of 3–10% over equivalent D-rated properties in the same area.
- Future mortgage stress testing: Some lenders are beginning to factor EPC ratings into long-term affordability assessments.
How Solar Panels Affect Your SAP Score
An EPC rating is driven by SAP (Standard Assessment Procedure) calculations. SAP models a property's energy costs based on construction, heating system, insulation, and low-carbon technologies including solar PV.
Solar panels contribute to your SAP score in two ways:
- Electricity generation credit: The SAP calculation credits the household with a proportion of the solar array's estimated generation, reducing the modelled energy cost.
- CO2 reduction: The displaced grid electricity reduces the property's estimated carbon emissions, which feeds directly into the environmental impact rating.
The size of the SAP improvement depends on the array size relative to the house's total energy demand. A large solar array on a well-insulated house can add 15–25 SAP points.
→ Before you read on — see what payback looks like for your roof in under a minute.
Real Case Studies from 2025
Case Study 1: Victorian Terrace, South London
Property: 3-bedroom end-of-terrace, built 1895, gas central heating, loft insulated to 270mm Before: EPC D (SAP 58) Installation: 6kWp south-facing array (16 x Jinko Tiger Neo panels), SolarEdge 5000H inverter After: EPC C (SAP 71) Rating change: D to C (+13 SAP points) Additional benefit: Qualified for NatWest Green Mortgage product, saving £1,800 over a 5-year fixed term
Case Study 2: 1970s Detached, Manchester
Property: 4-bedroom detached, cavity wall insulated, EPC D/low C borderline Before: EPC D (SAP 64) Installation: 8kWp east-west array (22 x Q Cells Q.Peak Duo panels), GivEnergy AIO 9.5kWh hybrid with battery After: EPC B (SAP 83) Rating change: D to B (+19 SAP points) Additional benefit: Landlord (renting the property) achieved compliance well ahead of the projected 2028 deadline
Case Study 3: New-Build Semi-Detached, Bristol
Property: 2020 new-build, already EPC B (SAP 80) from developer Before: EPC B (SAP 80) Installation: 4kWp south-facing array (10 x REC Alpha panels), Fronius Primo 3.0 inverter After: EPC A (SAP 92) Rating change: B to A (+12 SAP points) Additional benefit: First-time buyer was able to access an EPC A-specific mortgage product with a further 0.15% rate reduction
Case Study 4: Flat in Edinburgh (Top Floor)
Property: Top-floor tenement flat with roof access, electric storage heating Before: EPC E (SAP 45) — electric heating penalised heavily in SAP Installation: 3kWp array (8 x Panasonic HIT panels), SMA Sunny Boy, flat-roof mounting system After: EPC D (SAP 60) Rating change: E to D (+15 SAP points) Note: Solar alone could not reach C. Assessor noted that switching to a heat pump would achieve EPC C. This case illustrates that solar combined with other measures is most impactful for low-rated properties.
EPC Improvement: Realistic Expectations by Property Type
| Property Type | Typical SAP Gain from 6kWp Solar | Likely Rating Change |
|---|---|---|
| Modern well-insulated semi (EPC C/B) | 10–15 points | C to B or B to A |
| 1980s–90s detached (EPC D) | 12–18 points | D to C or D to B |
| Pre-1940s terrace (EPC D/E) | 8–13 points | Partial improvement; may not cross band |
| Flat (top floor) with roof access | 10–15 points | E to D or D to C |
Getting Your EPC Reassessed
Your EPC remains valid for 10 years, but you can commission a new assessment at any time. An EPC assessment from an accredited Domestic Energy Assessor (DEA) costs £60–£120 and can be arranged within a few days of your solar installation being commissioned and MCS-registered.
Important: Ensure you have your MCS installation certificate before the assessment. Without it, the assessor cannot credit the solar installation.
