An Energy Performance Certificate (EPC) tells you how energy-efficient a property is on a scale from A (most efficient) to G (least efficient). It affects your energy bills, your ability to let a property legally, and — increasingly — the mortgage rate you're offered. If you want to improve your EPC rating in the UK, understanding what drives the score is the first step. This guide explains the A–G scale, the regulations landlords must meet, and which improvements deliver the most bang for your buck.
Understanding the EPC: The A–G Scale and SAP Score
Every EPC is underpinned by a Standard Assessment Procedure (SAP) score — a number between 1 and 100 that models a property's energy performance based on insulation levels, heating system, glazing, and renewable generation. The score is converted to a band:
| EPC Band | SAP Score Range | Typical Annual Running Cost (3-bed semi) |
|---|---|---|
| A | 92–100 | ~£500–£700 |
| B | 81–91 | ~£700–£900 |
| C | 69–80 | ~£900–£1,200 |
| D | 55–68 | ~£1,200–£1,600 |
| E | 39–54 | ~£1,600–£2,200 |
| F | 21–38 | ~£2,200–£3,000 |
| G | 1–20 | £3,000+ |
Running costs are illustrative based on 2024 energy prices; they vary significantly by property size, location and occupancy.
The certificate also lists recommended improvements — each with an estimated cost and potential SAP uplift. Not all recommendations are equally efficient. For a deeper look at how to read and interpret your EPC report, see our how to read an EPC certificate guide.
MEES: What the Law Currently Requires
Minimum Energy Efficiency Standards (MEES) currently apply to the private rented sector in England and Wales. Since April 2020, landlords cannot grant a new tenancy on a property with an EPC below Band E. Since April 2023, this applies to all existing tenancies too.
The proposed changes: The previous government proposed raising the minimum to EPC C by 2028 for new tenancies and 2029 for all tenancies. The current government's Renters' Rights Bill (progressing through Parliament in 2025–26) is expected to confirm this timeline, though the final date may shift. Landlords with F or G-rated properties should act now — the cost of upgrading will only rise, and letting an F/G property is already a civil offence with fines up to £30,000.
Exemptions apply (e.g. if the required improvement would devalue the property by more than 5%, or listed building consent is refused) but must be registered on the PRS Exemptions Register.
The 5 Highest-Impact Improvements Ranked by SAP Points per £ Spent
| Improvement | Typical Cost | Estimated SAP Uplift | Notes |
|---|---|---|---|
| Loft insulation (270mm) | £300–£600 | +5–15 points | Most cost-effective single measure; DIY possible for accessible lofts |
| Cavity wall insulation | £300–£600 | +4–10 points | Only suitable for unfilled cavity walls; CIGA guarantee available |
| Heating controls (TRVs + programmer) | £150–£400 | +2–5 points | Low cost; often the missing link in otherwise well-insulated homes |
| Air source heat pump | £8,000–£15,000 (after BUS grant) | +10–20 points | BUS grant of £7,500 reduces upfront cost; requires adequate insulation first |
| Solar PV (4kWp) | £5,000–£8,000 | +10–25 points | Highest uplift potential; Smart Export Guarantee pays for surplus exported |
Sequencing matters: Insulate before installing a heat pump. A heat pump in a poorly insulated home will underperform and may not deliver the expected SAP improvement.
Solid Wall Insulation: The Expensive Option
If your property has solid walls (pre-1920 construction typically), cavity wall insulation isn't an option. External wall insulation (EWI) costs £8,000–£20,000 and can add 10–20 SAP points; internal wall insulation (IWI) costs £4,000–£12,000 but reduces floor area. ECO4 and GBIS grants may be available — check eligibility at trustmark.org.uk. For a full breakdown of all available government grants and how to apply, see our energy efficiency grants UK 2025 guide.
How to Challenge an EPC
EPCs are valid for 10 years and lodged on the national register (find your certificate at gov.uk/find-energy-certificate). If you believe your EPC is wrong, there are two routes:
Lodgement Error
If factual data is wrong (wrong wall construction type noted, missing insulation recorded incorrectly), contact the energy assessor directly. They can correct their records and re-lodge. There is no fee for a correction.
Full Reassessment
If you've made improvements since the EPC was issued, or if you believe the assessor's methodology was flawed, commission a new EPC from a different accredited assessor (£60–£120). The new certificate replaces the old one. Assessors must be accredited through schemes such as Elmhurst Energy or ECMK — check the register before instructing.
You cannot challenge an EPC through the assessor's accreditation body on grounds of disagreement with the outcome alone — there must be a demonstrable error.
When Your EPC Band Matters Most
Green Mortgages: Several lenders — including Barclays, NatWest, and Halifax — offer discounted rates (typically 0.1–0.3% lower) for properties with EPC A or B ratings. On a £250,000 mortgage, a 0.2% rate discount saves approximately £500 per year.
Rental Yield and Saleability: Research by Nationwide and the ONS consistently shows EPC C and above properties command a 3–5% price premium over equivalent F/G properties. For landlords, an F or G property is currently unlettable — the yield is literally zero until it's improved. For more on how EPC improvements affect saleability and buyer perceptions, see our EPC improvements to sell house faster guide.
First-Time Buyers: If you're buying an F or G property, factor the cost of improvements into your offer and budget. Use the EPC's recommended improvements section as a starting point, then get quotes — the EPC's cost estimates are notoriously optimistic. If mortgage lenders won't proceed because of the EPC rating, see our mortgage on a property with issues guide for specialist lending routes.
Victorian and Edwardian Properties: If you own a solid-walled pre-1919 home, EPC improvement is harder but not impossible. See our Victorian and Edwardian house renovation guide UK for the prioritised approach — including which IWI vs EWI option suits your property type.
Buyers and Movers: When buying a property, always check the EPC before making an offer — it affects running costs, mortgage availability, and your ability to let the property in future. For a complete guide to what to check before and after moving, see our moving house checklist UK guide.
Heat Pumps: If your EPC is C or above and you're considering switching from a gas boiler, our heat pump installation cost UK guide explains the BUS grant, suitability checklist, and payback periods in detail.
Spray Foam Insulation: If your roof space has spray foam insulation — whether installed under the Green Homes Grant or otherwise — be aware that this can create mortgage problems at resale regardless of your EPC rating. See our spray foam insulation UK guide for the full picture on lender positions and removal costs.
Buying or Selling: For a complete guide to how EPCs work in property transactions — who needs one, how long they're valid, how buyers should use the recommendations section, and MEES obligations for landlords — see our EPC guide for buyers and sellers.
For a comprehensive step-by-step improvement guide — covering the full fabric-first sequence, every measure ranked by SAP point gain and cost, what RdSAP assessors actually look for on the day, and the 2025 grants available — see our complete guide to improving your EPC rating.
For the full history of Green Deal finance, why it collapsed, and what has replaced it — ECO4, the Great British Insulation Scheme, the Boiler Upgrade Scheme, and how to stack them — see our Green Deal Finance UK: History and What Has Replaced It guide.