How to Improve Your EPC Rating from E to C

For Landlords

Under the Minimum Energy Efficiency Standards (MEES) regulations, landlords in England and Wales are currently prohibited from letting a property with an EPC rating below E. The government has consulted extensively on raising this minimum to C, with a proposed target that all new tenancies meet a C rating.

While the original 2025 and 2028 deadlines have been revised, the direction of travel is clear. Waiting until a hard deadline is announced before starting improvements is a costly strategy, both because energy efficiency retrofit work takes time and because the cheapest improvements become unavailable once other work has been completed. Landlords with properties rated E should treat an upgrade to C as a medium-term investment priority, not a distant regulatory concern.

For Homeowners

A higher EPC rating translates directly into lower energy bills. The difference between an E-rated and a C-rated home can amount to £600–£1,500 per year in energy costs, depending on property size and type. With energy prices remaining elevated, the payback period on many efficiency improvements has shortened considerably.

A C rating or above also opens access to green mortgage products offered by major lenders at preferential rates for energy-efficient properties and makes your property more attractive to buyers when you come to sell.

1. Switch to LED Lighting Throughout

This is the quickest and cheapest improvement you can make. EPC assessors record the percentage of fixed lighting outlets in a property that use energy-efficient bulbs. A property where less than 75% of fixed outlets use LEDs scores lower on this element.

Replacing all remaining halogen or incandescent bulbs with LED equivalents is a one afternoon job that costs between £50 and £150 for a typical three-bedroom property. LEDs use around 75% less energy than halogen equivalents and last significantly longer.

Alone, this improvement is unlikely to move you from E to C. But it contributes to your SAP score and is the obvious starting point given the near-zero outlay.

2. Loft Insulation

If your loft has less than 270mm of insulation or none at all, adding or topping up loft insulation is one of the single highest-impact EPC improvements available. Up to 25% of a home's heat is lost through an uninsulated roof.

The current standard is 270mm of mineral wool insulation in the loft. If you currently have 100mm or less, topping up to 270mm can add several points to your SAP score and is one of the most cost-effective measures on this list.

Typical cost: £400–£1200, depending on the property size, installed by a professional.

Potentially free: Under the Great British Insulation Scheme (GBIS) and the Energy Company Obligation (ECO4) scheme, homeowners and landlords with properties rated E, F, or G may be entitled to free loft insulation funded by the energy companies. Eligibility depends on property type and, in some cases, household income. Check your eligibility at gov.uk or through your energy supplier.

3. Cavity Wall Insulation

If your property was built between 1930 and 1995, it almost certainly has cavity walls, two layers of brick with a gap between them. If that cavity is not filled with insulation, you are losing a significant amount of heat through your walls every winter.

Cavity wall insulation involves injecting insulation material into the cavity through small holes drilled in the exterior brickwork. The holes are then filled and are barely visible. The process takes a few hours and causes minimal disruption.

Important: Cavity wall insulation is only suitable for certain wall types and conditions. A survey is needed first to confirm the suitability of your installer will carry this out before quoting.

Potentially free: Like loft insulation, cavity wall insulation is covered under the ECO4 and GBIS schemes for qualifying properties. Many households receive this improvement at no cost.

4. Hot Water Cylinder Insulation

If your property has an older hot water cylinder without a factory-fitted foam jacket, fitting an insulating jacket (also called a lagging jacket) is one of the cheapest energy efficiency improvements available. A properly fitted jacket that is at least 75mm thick can reduce heat loss from the cylinder by over 75%.

This is a DIY job in most cases. Cylinder jackets are available from hardware stores for as little as £15–£40. If your cylinder already has a factory-fitted foam jacket, no action is needed.

This improvement alone contributes to your SAP score and can bump a borderline EPC score up by a meaningful margin, particularly in properties where hot water is a significant energy cost.

5. Heating Controls Upgrade 

EPC assessors assess the type and quality of heating controls present in a property. Older properties often have basic on/off timers with no room-by-room temperature control. Upgrading to a programmer with room thermostat and thermostatic radiator valves (TRVs) improves your EPC score because it demonstrates that the heating system can be controlled efficiently.

Modern smart thermostats, such as those from Hive, Nest, or Tado, go further by learning heating patterns and allowing remote control via a smartphone. These are recognised in EPC calculations and can contribute to a rating improvement while also delivering measurable energy bill savings.

Cost range:

• Basic programmer and room thermostat: £100–£150 installed
• Smart thermostat system: £200–£350 installed

6. Upgrade to a Condensing Boiler 

If your property has an older non-condensing boiler, common in properties built before 2005, replacing it with a modern condensing combi or system boiler is one of the most significant single improvements you can make to an EPC rating.

Modern condensing boilers operate at 90%+ efficiency compared to around 60–70% for older non-condensing models. The SAP calculation is highly sensitive to boiler efficiency, meaning this upgrade typically delivers a substantial rating improvement.

Boiler replacement also triggers related improvements — new heating controls, better system balancing, and the opportunity to combine the work with other upgrades listed here.

Note for landlords: A boiler replacement also satisfies your obligation to keep the heating system in working order, provides an opportunity to combine with an annual gas safety certificate, and may extend the life of the heating installation by 15+ years.

👉 Book an annual Boiler Service to keep your heating system performing at its best

7. Solid Wall Insulation 

Properties built before around 1930 typically have solid walls rather than cavity walls, meaning cavity fill is not an option. Solid wall insulation, either internal dry lining or external cladding, is the solution, but it is the most expensive improvement on this list.

Internal insulation: Rigid insulation boards or stud walls with insulation are fitted on the inside face of external walls. Cost: £4,000–£8,000 for a typical semi-detached home. Some loss of internal floor space.

External insulation: Insulation is fixed to the outside of the building and covered with a render or cladding finish. Cost: £8,000–£14,000 for a typical semi-detached home. No loss of internal space, and can improve the property's appearance.

Grants available: Solid wall insulation is covered under the ECO4 scheme for eligible properties and households. For landlords, the Great British Insulation Scheme may also provide partial funding. Given the cost, checking grant eligibility before committing to this work is essential.

8. Secondary or Double Glazing

Single-glazed windows are a significant source of heat loss, and upgrading to double or triple glazing improves both your EPC rating and the thermal comfort of the property considerably.

Full double glazing replacement for an entire property is a significant investment (typically £5,000–£12,000), but the EPC impact is meaningful, particularly where a property currently has single glazing throughout.

Secondary glazing: A second pane fitted inside the existing window frame is a cheaper alternative at around £100–£300 per window and can achieve similar thermal performance without the cost of full replacement. It is also acceptable for listed buildings where replacement windows require consent.

ECO4 (Energy Company Obligation):

The current phase of the Energy Company Obligation requires large energy suppliers to fund energy efficiency improvements in low-income and fuel-poor households. Qualifying properties with EPC ratings of E, F, or G may be eligible for free insulation, boiler upgrades, or heat pump installation. Eligibility is primarily based on household income and benefits status for owner-occupiers. For landlords, eligibility through ECO4 is more limited, but certain routes exist, particularly through local authority flex arrangements.

Check eligibility: Contact your energy supplier directly or visit gov.uk/find-energy-grant.

Great British Insulation Scheme (GBIS):

Specifically targeting properties with EPC ratings of D or below, this scheme provides free or heavily subsidised insulation (loft, cavity wall, or solid wall) for qualifying households. Unlike ECO4, eligibility is not solely income-based; the property's EPC rating is the primary criterion.

Boiler Upgrade Scheme (BUS):

This scheme provides grants toward the installation of heat pumps as a replacement for existing gas or oil boilers:

• Air source heat pump: £7,500 grant
• Ground source heat pump: £7,500 grant

A heat pump installation, when combined with insulation improvements, can push a property from E to B or even A in some cases, though the upfront investment is substantial even with the grant.

Yes. Improvements to your property do not automatically update your EPC rating. You need to commission a new EPC assessment from a qualified Domestic Energy Assessor (DEA) once the work is complete. The assessor will inspect the property, verify the improvements, and issue an updated certificate reflecting the new rating.

An EPC assessment for a standard domestic property typically costs between £60 and £120 and takes 45–90 minutes. The new certificate is valid for 10 years.

For landlords, a new EPC showing a satisfactory rating is also your evidence of compliance with MEES regulations — keep it on file with your other property certificates.

👉 Book an Energy Performance Certificate — Get an Instant Quote

If your property currently has an E rating, here is a step-by-step starting point:

1. Read your existing EPC report — the recommendations section lists the specific improvements that will have the most impact on your property, with estimated costs and rating uplift for each.
2. Check grant eligibility first — before spending anything, find out what you're entitled to for free under ECO4 or GBIS. Insulation and sometimes boiler replacements can be fully funded.
3. Start with loft and cavity wall insulation — these deliver the highest EPC impact at the lowest net cost, especially if grant-funded.
4. Upgrade your boiler if it's over 15 years old — this is the single biggest SAP score improvement available for most gas-heated properties.
5. Add heating controls — combine this with the boiler upgrade if you're replacing the boiler anyway.
6. Book a new EPC — once improvements are complete, get your updated certificate issued promptly.

How much does it cost to improve an EPC from E to C? For most properties, the combination of loft insulation, cavity wall insulation, a boiler upgrade, and heating controls delivers the necessary improvement. If you qualify for ECO4 or GBIS funding, the out-of-pocket cost for insulation work can be zero. A boiler replacement — the most expensive element — typically costs £1,500–£3,000 after any applicable incentives.

Can I improve my EPC rating without a boiler replacement? Yes, in some cases. If your property has relatively modern heating but poor insulation, addressing the insulation alone may be enough to reach a C rating. Your existing EPC recommendations will indicate the most efficient route for your specific property.

Does adding solar panels improve an EPC rating? Yes, significantly. Solar photovoltaic (PV) panels are one of the most powerful EPC improvements available for owned properties. A standard 4kW roof-mounted system can add 10–20 SAP points in many cases. The upfront cost is higher (typically £5,000–£8,000), but feed-in tariff income, reduced bills, and the EPC uplift make this a strong long-term investment.

How long does an EPC assessment take? A domestic EPC assessment typically takes 45–90 minutes for a standard property. The DEA will inspect your heating system, insulation, windows, lighting, and building fabric. The certificate is usually issued digitally within 24–48 hours.

Does an EPC rating affect mortgage rates? Yes. An increasing number of mortgage lenders offer preferential rates — known as green mortgages — for properties with EPC ratings of C or above. The rate differential varies by lender but can make a measurable difference over a 25-year mortgage term.