EPC Ratings Explained: What A to G Really Means

A to G scale based on a SAP score from 1 to 100
The UK average is D — most homes built between 1950 and 1990
Landlords must achieve a minimum E rating to legally let a property
Rating affects annual energy costs, mortgage terms, and sale price
Most D-rated homes can reach C with one or two targeted improvements

What are EPC ratings?

An EPC rating is a letter grade from A to G that summarises how energy-efficient a property is. It is derived from a numerical SAP (Standard Assessment Procedure) score calculated on a scale of 1 to 100. The higher the number, the more energy-efficient the property and the lower its running costs. Rating A covers SAP scores of 92 to 100, while rating G covers 1 to 20.

The score is calculated by a qualified Domestic Energy Assessor using the RDSAP (Reduced Data Standard Assessment Procedure) methodology. This takes into account the building fabric — walls, roof, floors, and windows — alongside the heating system, hot water provision, lighting, and any renewable energy sources present. The result is a standardised figure that allows properties of different ages, sizes, and construction types to be fairly compared.

Every EPC also shows a potential rating: the score your property could achieve if all recommended improvements were carried out. The gap between your current and potential rating tells you roughly how much room for improvement exists, and the accompanying recommendations page prioritises the measures most likely to have an impact.

92–100 · Most efficient

81–91

69–80

55–68 · UK average

39–54

21–38

1–20 · Least efficient

EPC ratings run from A (most efficient) to G (least efficient). The average UK home is rated D, with a SAP score of around 60.

Rating by rating: what each band really means

Each rating band covers a range of SAP scores and corresponds to a recognisable type of property in the UK housing stock. Here is what you can expect to find at each level, including approximate annual energy costs for a typical 3-bedroom semi-detached home.

SAP 92–100

The overachiever

Typical properties: Passivhaus new builds, properties with air source or ground source heat pumps, solar PV panels, triple glazing, and thick insulation throughout. Near-zero carbon homes.

Approximate annual energy costs: Under £500 for a typical 3-bed.

MEES compliance: Well above the minimum. Meets any foreseeable future standard.

Rating A properties are still rare in the UK — fewer than 1% of homes hold this grade. They are almost exclusively modern new builds built to the highest specification, or older properties that have undergone comprehensive deep retrofit. Heat pumps and solar are usually central to achieving this band.

SAP 81–91

The high performer

Typical properties: Post-2010 new builds, recently retrofitted homes with a modern condensing boiler, cavity wall insulation, 270mm loft insulation, double glazing, and good heating controls.

Approximate annual energy costs: £500–£900 for a typical 3-bed.

MEES compliance: Exceeds the minimum by a significant margin.

B-rated properties represent around 5% of UK homes. Most are post-2000 builds where the developer used high-quality insulation and efficient heating as standard. An older property can reach B with a combination of external or internal wall insulation, a heat pump, and solar panels, but this typically requires significant investment.

SAP 69–80

Above the curve

Typical properties: Post-1990 homes built to then-current building regulations, or pre-1990 properties that have received cavity wall insulation, loft insulation to at least 200mm, and a modern boiler.

Approximate annual energy costs: £900–£1,300 for a typical 3-bed.

MEES compliance: Above the current minimum. Meets the proposed future standard.

C is the rating the government has signalled it wants all rental properties to reach. Around 40% of UK homes are currently rated C or above, and it is achievable for most D-rated properties with one or two targeted improvements. If your EPC recommendation report includes cavity wall insulation or a boiler upgrade, reaching C is likely within reach without major disruption.

SAP 55–68

The UK average

Typical properties: Post-war semi-detached and terraced homes built between the 1950s and 1980s, typically with partial insulation, double glazing, and a boiler that is less than 15 years old.

Approximate annual energy costs: £1,300–£1,800 for a typical 3-bed.

MEES compliance: Above the current minimum of E.

D is the most common rating in England and Wales, covering roughly 35% of homes. If your property was built between 1950 and 1990, has had some but not all insulation improvements, and uses a standard gas boiler, a D is the most likely result. Moving to a C from here often costs less than £2,000 in practice. The most common route is topping up loft insulation and installing cavity wall insulation if the walls are suitable.

SAP 39–54

The bare minimum

Typical properties: Pre-1945 solid-wall terraces and semis, or post-war properties with no loft insulation, single glazing, or an older inefficient boiler. Also common in converted flats with shared heating or no insulation upgrades since construction.

Approximate annual energy costs: £1,800–£2,400 for a typical 3-bed.

MEES compliance: Meets the current legal minimum for renting. Cannot be let if it falls any lower without improvements or a registered exemption.

E is the legal floor for landlords under the current Minimum Energy Efficiency Standards. If you own a rental property at E, you are compliant for now, but you are at risk if proposed changes raise the minimum to C. Improvements that are most likely to lift an E to a D or C include installing a new condensing boiler, adding loft insulation, and upgrading to double glazing.

SAP 21–38

Needs attention

Typical properties: Pre-1919 solid-wall Victorian and Edwardian terraces or semis with no wall insulation, single glazing throughout, and either a very old boiler or electric storage heaters. Unmodernised rural properties are also common at this level.

Approximate annual energy costs: £2,400–£3,200 for a typical 3-bed.

MEES compliance: Does not meet the current minimum. Cannot be legally let without a registered exemption.

F-rated properties are below the legal threshold for renting and face significant restrictions. However, the improvements that move a property out of F often have the largest relative impact, because the baseline is so low. Replacing a defunct heating system, adding secondary or double glazing, and insulating the loft can together add 20 or more SAP points in the right circumstances.

SAP 1–20

The fixer-upper

Typical properties: Unmodernised Victorian or Edwardian properties with solid walls, no insulation anywhere, single glazing, and either no central heating at all or individual electric heaters. Rural properties without mains gas are at particular risk of a G rating.

Approximate annual energy costs: Over £3,200 for a typical 3-bed, often significantly more.

MEES compliance: Well below the legal minimum. Cannot be let under any circumstances without a valid exemption.

G is the least common rating in England — fewer than 2% of homes — but the costs for occupiers are severe. The positive side is that almost any improvement has a meaningful effect at this level. Even basic measures like draught-proofing, loft insulation, and boiler replacement can lift a G into E territory, making the property legally rentable and dramatically cheaper to heat.

What affects your EPC rating?

Your EPC score is the result of how the building performs as a whole rather than any single feature. The assessor records specific data for each element below, which is then fed into the RDSAP calculation to produce the final SAP score.

Wall construction and insulation: Walls are the biggest single factor in most older properties. Cavity walls with insulation score far better than uninsulated solid walls. Solid walls can be insulated internally or externally, but at significantly higher cost than cavity fill.
Roof and loft insulation: Heat rises, so a poorly insulated loft is a major source of heat loss. Topping up existing insulation to 270mm is one of the most cost-effective improvements available and can add several SAP points on its own.
Floor insulation: Suspended timber floors lose a surprising amount of heat, particularly in pre-1919 properties. Solid concrete floors are assessed differently and typically score better than uninsulated timber floors.
Windows and glazing: Single glazing is heavily penalised in the SAP calculation. Double glazing is the baseline expectation. Triple glazing adds further points but the marginal gain over double is smaller.
Heating system: The boiler type, fuel, age, and efficiency rating all affect the score. A modern A-rated gas condensing boiler scores well. Electric storage heaters, old back boilers, and LPG or oil systems typically score lower for the same level of heat output.
Heating controls: Having a room thermostat, a programmer or timer, and thermostatic radiator valves (TRVs) all contribute positively. Properties without any controls score worse regardless of boiler efficiency.
Hot water system: Whether hot water is stored in a cylinder or produced on demand (combi boiler), and how well-insulated any cylinder is, both affect the score.
Lighting: The percentage of fixed light fittings with low-energy bulbs (LED or CFL) contributes to the final score. Full LED lighting adds a small but measurable number of SAP points.
Renewable energy: Solar PV panels, solar thermal, heat pumps, and biomass boilers all increase the SAP score, sometimes substantially. A solar PV array can add 5 to 15 points depending on system size and orientation.
Thermal bridges and air permeability: Gaps around window frames, poorly fitted doors, and uninsulated junctions between building elements allow heat to escape. While difficult to measure precisely in an RDSAP assessment, they influence the default assumptions used in the calculation.

Average EPC ratings in the UK

The national average EPC rating in England is D, with a mean SAP score of approximately 60. This figure has risen slowly over the past decade as more properties have received insulation improvements and boiler upgrades, but the majority of UK housing stock is still pre-1970s construction that requires significant investment to reach C.

London is often below the national average. The capital has a higher proportion of pre-1919 solid-wall Victorian and Edwardian terraces and converted flats than most other parts of the country, many of which have never had their walls insulated. The density of the housing stock also makes external wall insulation impractical in many streets, leaving internal wall insulation as the primary option — which is more disruptive and expensive.

Newly built properties are almost all C-rated or above, because building regulations have required increasingly high levels of insulation and heating efficiency since the 1990s. Properties built after 2010 are typically B-rated as standard. At the other end of the scale, rural properties in England — particularly those off the gas grid that rely on oil or LPG boilers — tend to score lower because these fuel types are penalised in the SAP calculation relative to mains gas.

Minimum EPC rating for landlords

The Minimum Energy Efficiency Standards (MEES) set a legal floor on the EPC rating a rental property must hold before a tenancy can begin. These regulations apply to all domestic private rented properties in England and Wales, including houses, flats, and HMOs.

Current law (since 2020)

Rental properties must have a minimum EPC rating of E before a new tenancy or tenancy renewal can start. Properties rated F or G cannot be legally let unless the landlord has registered a valid exemption on the PRS Exemptions Register.

Penalties: Local authorities can issue fines of up to £5,000 per property for non-compliance with MEES, depending on how long the breach has continued. The breach is also recorded on a public non-compliance register for 12 months.

There has been ongoing government consultation about raising the minimum to C for all new tenancies. Although the timeline has shifted, landlords with properties currently rated D or E should plan ahead for the investment needed to reach C rather than waiting for enforcement to arrive. Read our full guide to MEES regulations and EPC requirements for landlords for more detail.

How to improve your EPC rating

Your EPC recommendation report lists the specific measures most likely to improve your score, ranked by estimated cost and impact. The five most common improvements, and what they typically achieve, are set out below.

1. Loft insulation (270mm): If your loft has less than 100mm of insulation or none at all, topping it up to 270mm is typically the cheapest and highest-impact improvement available. Cost: £300–£600. Typical rating gain: 2–5 SAP points.
2. Cavity wall insulation: Properties built between the 1930s and 1990s with unfilled cavity walls can gain significant SAP points from a professional cavity fill. The installation takes half a day and is non-disruptive. Cost: £500–£1,500. Typical rating gain: 3–8 SAP points.
3. Boiler replacement: Replacing an old non-condensing boiler (pre-2005) or a boiler with a SEDBUK efficiency rating below 80% with a modern A-rated condensing model typically adds 3–10 SAP points. Cost: £2,000–£3,500 installed. Often enough alone to move D to C.
4. Heating controls: If your property lacks a room thermostat, programmer, or TRVs, installing them is inexpensive and adds SAP points. Cost: £150–£400. Typical rating gain: 1–3 SAP points depending on what is missing.
5. Solar PV panels: A 4kWp south-facing array can add 5–15 SAP points and often pushes a C-rated home to B. Cost: £6,000–£9,000. Available through the Smart Export Guarantee, which pays you for unused electricity exported to the grid.

Read our full guide to improving your EPC rating →

How Kubo can help

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Frequently asked questions

What is a good EPC rating?

A rating of C or above is generally considered good. Most mortgage lenders, buyers, and lettings regulations view C as the benchmark. Ratings of A or B are excellent and associated with very low energy bills, but are relatively rare in existing UK housing stock.

What is the average EPC rating in the UK?

The average EPC rating in the UK is D, with a SAP score of around 60. London properties often score lower than the national average because the capital has a higher proportion of older, pre-1919 housing stock that is harder to insulate. Newly built properties are almost all C or above.

Can I sell a house with an EPC rating of F?

Yes, you can sell a property with an F rating. There is no minimum EPC requirement for the sale of residential property. However, you are legally required to have a valid EPC in place before marketing the property. Buyers and their lenders may factor the poor rating into their offer or mortgage terms, so it is worth understanding the impact before listing.

What EPC rating do I need to rent out a property?

Under the Minimum Energy Efficiency Standards (MEES), rental properties in England and Wales must have a minimum EPC rating of E before a new tenancy can begin. Properties rated F or G cannot be legally let without a registered exemption. Read our EPC guide for landlords for full details.

How much does it cost to improve from D to C?

The cost varies depending on your property and what improvements are needed. Common upgrades that move a D-rated home to C include cavity wall insulation (£500–£1,500), loft insulation top-up (£300–£600), and upgrading to a modern condensing boiler (£2,000–£3,500). Many properties can reach C with just one or two targeted measures, and some landlords qualify for government-funded improvements through schemes such as ECO4.

Does a new boiler improve my EPC rating?

Yes, in most cases. Replacing an old G-rated or non-condensing boiler with a modern A-rated condensing boiler can add between 3 and 10 SAP points to your score, which is often enough to move a D-rated home to a C. The exact improvement depends on the rest of your property's efficiency and what controls are already in place.

How long does an EPC last?

An EPC is valid for 10 years from the date it is issued. You are not required to renew it during that period, but it is worth getting a new one if you have made energy efficiency improvements to your property, as those changes will not be reflected in the existing certificate and could be worth points.

What happens if my EPC expires?

If your EPC expires, you cannot legally market a property for sale or start a new tenancy until you obtain a fresh one. Marketing a property for sale without a valid EPC can result in a fine of up to £200, while letting without one can result in a penalty of up to £5,000. You can check whether your property has a current EPC and when it expires on the GOV.UK energy certificate register.

MEES regulations explained
Minimum Energy Efficiency Standards, exemptions, penalties, and what the proposed C rating requirement means for landlords

EPC for landlords
Minimum ratings, legal requirements, fines, and how to bring a sub-standard property up to the minimum before a tenancy starts