EPC Rating: How to Improve Your Energy Performance Certificate from F or G to C or Above
If you want to know how to improve your EPC rating in the UK, you are in the right place. Whether you are a landlord facing minimum energy efficiency standards, a homeowner trying to cut fuel bills, or a buyer inheriting a leaky Victorian terrace, moving your energy performance certificate from F or G to C or above is achievable — and in many cases part-funded by government grants. This guide explains the EPC band system, which improvements deliver the biggest SAP score gains per pound spent, and how to sequence the work.
What Is an EPC and How Is It Scored?
An Energy Performance Certificate rates a property's energy efficiency on a scale of A (most efficient) to G (least efficient). The rating is calculated using the Standard Assessment Procedure (SAP), a government methodology that models the property's energy use based on construction, insulation, heating system, glazing, and lighting. SAP scores run from 1 to 100+:
| Band | SAP Score | Typical Annual Energy Cost |
|---|---|---|
| A | 92–100+ | ~£500–£700 |
| B | 81–91 | ~£700–£900 |
| C | 69–80 | ~£900–£1,300 |
| D | 55–68 | ~£1,300–£1,800 |
| E | 39–54 | ~£1,800–£2,500 |
| F | 21–38 | ~£2,500–£3,500 |
| G | 1–20 | £3,500+ |
An EPC is produced by a Domestic Energy Assessor (DEA) accredited through organisations such as Elmhurst Energy or Stroma. Certificates are valid for ten years and lodged on the national EPC Register at gov.uk. The certificate includes a recommended improvement report showing which measures would lift the rating and by how much — this is your action plan.
What Affects Your EPC Score?
The SAP calculation weighs four main areas:
- Insulation — loft, walls (cavity or solid), floor, and roof. Poor insulation is the single biggest drag on an EPC score.
- Heating system — boiler type (condensing vs non-condensing), controls (programmers, TRVs), and fuel type. Gas condensing boilers score better than older G-rated models; heat pumps score better still.
- Glazing — single-glazed windows score poorly. Double-glazing to at least 1.4 W/m²K and secondary glazing both uplift scores.
- Lighting — low-energy LED bulbs in 75%+ of fixed fittings are assessed. A simple bulb swap adds a handful of SAP points at negligible cost.
Improvements Ranked by SAP Score Uplift
The table below ranks common measures by typical SAP points gained per £1,000 spent — the most cost-effective first.
| Measure | Typical SAP Uplift | DIY? | Approx. Cost | Cost per SAP Point |
|---|---|---|---|---|
| LED lighting (all fittings) | +2–4 pts | Yes | £50–£200 | Very low |
| Loft insulation (270mm, empty loft) | +10–15 pts | Possible | £300–£600 | Very low |
| Cavity wall insulation | +8–12 pts | No (professional) | £500–£1,500 | Low |
| Draught-proofing | +2–4 pts | Yes | £100–£300 | Low |
| Condensing boiler (replacing G-rated) | +10–15 pts | No | £2,000–£4,500 | Medium |
| Hot water cylinder insulation jacket | +1–3 pts | Yes | £15–£30 | Very low |
| Double glazing (replacing single) | +2–5 pts per window | No | £400–£800/window | Medium |
| External wall insulation (solid walls) | +15–25 pts | No | £8,000–£25,000 | Medium–High |
| Internal wall insulation (solid walls) | +12–20 pts | No | £4,000–£13,000 | Medium |
| Air source heat pump | +8–15 pts | No | £7,000–£13,000 | Medium |
| Solar PV (3–4 kWp) | +10–25 pts | No | £5,000–£8,000 | Low–Medium |
Start With the Fabric First
Energy professionals recommend a 'fabric first' approach: seal and insulate before upgrading heating or installing renewables. A poorly insulated house with a heat pump will still score badly and will cost more to run than a well-insulated house with a good gas boiler.
For F or G-rated properties the typical improvement pathway is:
- LED lighting — immediate, cheap, small uplift
- Loft insulation to 270mm — biggest bang for buck if the loft is accessible
- Cavity wall insulation — if cavity walls exist (most post-1930 homes)
- Draught-proofing — windows, doors, letterboxes, loft hatches
- Boiler replacement — if the current boiler is pre-2005 or non-condensing
- Wall insulation — EWI or IWI for pre-1930 solid-wall homes
- Renewables — solar PV, heat pump once the fabric is sorted
A typical F-rated semi-detached house with cavity walls and an old boiler can often reach a C simply with steps 1–5 for £3,000–£6,000 before grants.
DIY vs Professional Installation
Some measures are genuinely DIY-friendly:
- LED bulbs: straightforward swap, no qualifications needed
- Draught-proofing: brush strips, sealant, and letterbox covers are available from DIY retailers for under £200
- Hot water jacket: push-fit lagging jackets from £15 at any hardware store
- Top-up loft insulation: mineral wool rolls can be laid by a confident DIYer if the loft is floored or easy to access
Most other measures require qualified professionals:
- Cavity wall insulation must be installed by a BBA-approved contractor and registered under CIGA (Cavity Insulation Guarantee Agency) for a 25-year guarantee
- Boiler installation requires a Gas Safe registered engineer
- Heat pumps must be installed by an MCS-accredited contractor to qualify for government grants
- Solar PV installation requires an MCS-accredited installer and notification to your Distribution Network Operator
Government Schemes That Can Fund the Work
ECO4 (Energy Company Obligation)
Large energy suppliers are obliged to fund energy efficiency measures in low-income and fuel-poor homes. ECO4 targets households in EPC bands D–G who are on qualifying benefits (Universal Credit, Pension Credit, Child Benefit, etc.) or referred via local authority 'LA Flex' routes. Eligible measures include insulation, boiler upgrades, and heat pumps — potentially fully funded. ECO4 runs to March 2026; check eligibility at trustmark.org.uk/find-a-business or your energy supplier's website.
Great British Insulation Scheme (GBIS)
GBIS offers insulation grants to households in EPC bands D–G with council tax bands A–D in England. Unlike ECO4 it is not restricted to benefit claimants. A single insulation measure (typically loft or cavity wall) can be fully funded or heavily subsidised. Check eligibility at gov.uk/great-british-insulation-scheme.
Boiler Upgrade Scheme (BUS)
The BUS provides a £7,500 upfront grant for air source heat pumps and ground source heat pumps, and £5,000 for biomass boilers. The grant is applied by your MCS-accredited installer at point of purchase — you do not claim it yourself. BUS runs to March 2028. Note: heat pumps often require a well-insulated property to operate efficiently; pair with loft and wall insulation first.
Warm Home Discount
The Warm Home Discount provides a £150 annual reduction on electricity bills for eligible households. It does not fund physical measures but reduces running costs.
Landlord Obligations: MEES
The Minimum Energy Efficiency Standards (MEES) under the Energy Efficiency (Private Rented Property) (England and Wales) Regulations 2015 require:
- From April 2020: All new tenancies must be EPC E or above
- From April 2023: All existing tenancies must be EPC E or above
Landlords with properties rated F or G may not legally let them unless a valid exemption is registered on the PRS Exemptions Register. Exemptions include: all cost-effective improvements costing up to £3,500 (net of third-party funding) already made, or specific circumstances such as third-party consent refused (e.g. listed building).
The government has proposed raising the minimum to EPC C by 2028 for all private rented properties in England and Wales. While not yet law, landlords with F or G properties should plan remediation now to avoid the cost pressure of a hard deadline. A civil penalty of up to £30,000 per property applies for MEES breaches.
For landlords operating HMOs, note that EPC improvements often overlap with fire safety and building fabric obligations — see the HMO fire safety requirements guide for how insulation and window upgrades interact with escape route and fire door requirements.
Scotland note: Scottish MEES requires EPC D for new tenancies (since December 2020) and EPC C as the proposed target.
How to Commission an EPC Reassessment
Once improvements are complete, commission a new EPC from an accredited DEA (find one at epcregister.com or elmhurstenergy.co.uk). Cost: typically £60–£120 for a residential property. The DEA will visit, inspect, and lodge the updated certificate within a few days. If you believe a current EPC contains factual errors (wrong wall type recorded, loft insulation not measured), you can raise a dispute with the accreditation scheme that issued the certificate.
Related Guides
- Retrofit Insulation: EWI vs IWI — PAS 2035 requirements, ECO4/GBIS grant eligibility, and the comparative costs of external vs internal wall insulation for solid-wall homes
- Heat Pump Installation: ASHP vs GSHP, the BUS Grant, and Planning Rules — why the BUS grant EPC outstanding recommendations requirement catches applicants out, and how SAP points from insulation affect heat pump sizing
- Loft Conversion Planning Permission UK — if your loft conversion plans include insulation upgrades, how PD rights and Building Regs Part L interact with EPC improvements
- Listed Building Consent UK — EPC exemptions for listed buildings and how MEES interacts with heritage consent requirements
- EPC Guide for Buyers and Sellers — how EPCs work in transactions, what buyers should look for in the recommendations section, and MEES obligations for landlords explained from first principles
- Solar Panels and Planning Permission — how solar PV installation adds 8–15 SAP points and what planning rules apply before you install
Improving your EPC score from F or G to C is a project with a defined roadmap — insulation first, heating next, renewables last. Renovate Me can generate a personalised step-by-step improvement plan for your specific property, budget, and timeline, with cost estimates for every measure. Upload your property details at renovate-me.madethis.app to get started.