How to Read an Energy Performance Certificate

An Energy Performance Certificate, or EPC, rates how energy efficient a building is, with ratings from band A, very efficient, down to band G, inefficient¹. The rating is a score on a scale of 1 to 100, split into those lettered bands, and the certificate shows both the rating the building has today and the rating it could reach with the improvements the report lists². Each certificate is valid for 10 years and can be used for multiple sales or lettings within that period³. An assessment generally costs between £35 and £100, and the resulting document is lodged on a public register anyone can search for free⁴.

Reading the certificate well means knowing which parts are measured facts about the building and which are modelled estimates. The assessor inspects the property and records its construction, heating and lighting; the score itself is then calculated from that information, not from your actual bills⁵. This page walks through each part of the document: the bands, the four main sections, the recommendations, the cost figures, the U-values behind them, where the rules come from, and what the certificate does and does not tell you about your home's energy independence.

Understanding the energy performance certificate and its contents

An EPC explains how energy efficient a building is and how it could be improved⁵. It is produced using standard information about buildings, which is what allows a buyer or tenant to compare the likely heating and lighting costs of different properties before signing anything³. Alongside the headline rating, the certificate gives the property's heating source, its estimated carbon emissions and its estimated energy cost⁷.

To produce it, an accredited energy assessor inspects the property and uses information such as the type of construction, the heating system and the lighting⁸. The assessment records specific details⁹:

• the dwelling type
• the floor area
• the construction type
• the insulation
• the heating system
• the ventilation
• the lighting

Two things follow from this that are worth holding in mind whenever you read a certificate. First, the assessment reflects the energy performance of the building itself, not the way it is used by its occupants⁵, so a cold house with an efficient fabric can score well while a warm, wasteful one scores badly. Second, the assessor records what can be seen and evidenced on the day, so anything hidden, such as insulation that was installed but not documented, may not be credited. If you are preparing for an assessment, gathering evidence of past work is the single most useful thing you can do; if you are reading someone else's certificate, treat the fabric descriptions as recorded assumptions rather than verified measurements. For the practical steps of commissioning a survey, see getting an EPC for your home, and for fixing mistakes, challenging an EPC error.

Decoding the rating scale from A to G

The headline rating is a number from 1 to 100, and that number places the building in one of the lettered bands². The bands run from A at the top to G at the bottom¹. The published score ranges include band B at 81 to 91, band E at 39 to 54, and band G at 1 to 20, the least efficient¹⁰. The rating is measured on a scale divided into 100 units⁴.

Two ratings appear on the certificate, and both use the same 1 to 100 scale and A to G bands: the energy efficiency rating and the environmental impact rating, which reflects carbon dioxide emissions². The number that matters most to most readers is the energy efficiency rating, because that is the one quoted in adverts and used by policy. The potential rating beside it is not a prediction; it is a recalculation showing what score the same building would achieve if every listed improvement were carried out. The gap between the two arrows on the chart is therefore a measure of how much assessed improvement the assessor believes the fabric and heating system could support, and it is worth asking why any large gap exists before treating the potential figure as achievable.

The four sections that make up an EPC

A domestic EPC should contain, at minimum, the building's asset rating against a benchmark, the recommendation report, a reference number and date of issuance, the building address, and the building's total useful floor area¹¹. In Scotland, the production of an EPC is described as a four-part process: an assessment by an accredited person, a calculation using an approved methodology, lodgement on a national register, and production of a certificate to an agreed Scottish format¹². The Scottish certificate therefore looks different from the England and Wales version, but the underlying logic is the same.

Alongside the headline figures, the certificate rates individual features of the home, such as walls, roof, floor, windows, heating and lighting, each on a scale of 1, Very Poor, to 5, Very Good⁶. This feature-by-feature section is where a careful reader earns their keep. The headline band is a single number, but the feature ratings show where the points are being lost: a band D home with a band A heating system and a Very Poor wall rating is a very different proposition from a band D home that is uniformly mediocre. The feature ratings are also the easiest place to spot an assumption that does not match the house, because they state what the assessor believed about each element, and you can compare that against what you know or can see. If a feature rating looks wrong, that is the ground on which a certificate can be challenged.

How suggested upgrades appear in the recommendation report

Every EPC is accompanied by a recommendations report, which provides more detailed information about improvement measures⁵. The report sets out the cost effective measures the owner can take to improve the property's energy efficiency and its rating, from low-cost steps such as low energy bulbs through to upgrading insulation³. In Scotland, following the reform consultation, "recommendations" on EPCs have been renamed "Potential Improvement Options"¹³, so a Scottish certificate may use different wording for the same section.

The recommendations are generated by the calculation methodology from the recorded features, not written bespoke for the house, so they are worth reading with judgement. A recommendation is only as good as the assumptions behind it: if the assessor recorded the walls as uninsulated when they are insulated, the report may recommend work that has already been done. The recommendations also come without any assessment of whether they suit the particular building or household.

There is evidence that households act on this section. Among people aware of EPCs, 32% recalled seeing the section of their home's certificate that recommends ways to improve energy efficiency, and of those who had seen the recommendations, two in three, 65%, said they had made changes, small or large, based on what they read¹⁴. For the funding side of carrying out listed improvements, see checking which energy grants you qualify for and applying for a home energy grant.

Running cost and carbon estimates on the certificate

The certificate contains information on potential energy costs and carbon dioxide emissions, alongside the coloured chart showing how efficient the building is or could be³. In England and Wales, an EPC gives an estimation of the annual energy costs for the property⁴. These figures are modelled, not metered: they are calculated from the standardised assessment of the building, run to standard assumptions about how a typical household occupies it.

The basis of the calculation matters more than most readers realise. EPC ratings are based on £/m2/yr, pounds of energy cost per square metre per year, which means the relative price of gas and electricity has a significant impact on the score⁴. A select committee report put the consequence plainly:

A house heated by gas can therefore outrank an identical house heated by electricity, even where the electric home emits less. The estimated cost figures on the certificate are also tied to the energy prices assumed at the time of the calculation, so a certificate several years old may understate or overstate what the house actually costs to run today. Treat the cost figures as a comparison tool between properties assessed on the same basis, not as a forecast of your bills, which will depend on your own usage, your tariff and your supplier.

U-values: how building fabric shapes the score

Underneath the feature ratings sits a technical measure: the U-value, the rate at which heat passes through a building element. Lower is better. As a worked example from official guidance, cavity wall insulation under a government scheme is assessed against a U-value of 0.55 W/m2K¹⁶. The feature ratings on the certificate, from 1, Very Poor, to 5, Very Good, are the reader-facing expression of these underlying fabric numbers⁶.

The U-value matters because it is the point at which the certificate's assumptions meet physical reality. The assessor does not usually drill into walls or lift floorboards; the U-values in the calculation are assumed from the recorded construction type and age, adjusted only where insulation is present and evidenced. This is why two houses of the same age and type can receive different ratings if one owner has documentary proof of insulation work and the other does not. It is also why the fabric figures are the most common source of EPC errors, and the most common ground for a challenge.

The way fabric performance feeds the rating is itself under review. The Climate Change Committee has advised both governments that reforms to EPC rating metrics should be applied alongside wider improvements to the EPC system to improve the quality of assessments and use of data¹⁷, and has suggested EPCs could be expanded to provide information on risks posed by climate change and ways to reduce these¹⁸. Scotland's new rating system is intended to give clearer information on the fabric energy efficiency of a property, alongside the emissions, efficiency and running costs of its heating system¹⁹.

The legal basis for the rules

The legal root of the EPC is the EU Energy Performance of Buildings Directive, first adopted in 2002²⁰. Legislation covering EPCs was introduced across the UK in 2008, transposing that directive and retained in UK law following EU Exit¹³. In England and Wales, the energy performance of buildings regime is currently governed by the Energy Performance of Buildings Regulations 2012²¹, which include the duty, defined in regulation 34, requiring an EPC when a building is constructed, sold or let²². In Scotland, the directive was transposed by the Energy Performance of Buildings (Scotland) Regulations 2008, under which an EPC must contain the asset rating, a reference value, cost effective recommendations, the address, the name of the approved organisation and the issue date¹².

The EU directive itself has moved on, even though the UK is no longer bound by it. The recast Directive was adopted in April 2024, and it aims at reducing greenhouse gas emissions by at least 60% in the building sector by 2030 compared to 2015, and at achieving a highly energy efficient, zero-emission building stock by 2050²⁰. UK policy points the same direction: EPCs are required when any building is sold, rented out or constructed, and sometimes after refurbishment work, under the framework of the carbon budget delivery plan²³.

One divergence within the UK is important. EPCs in Scotland remain a source of information only, unlike in other parts of the UK where they are linked to minimum energy efficiency standards for rented homes²⁴. So the same certificate that is merely advisory in Scotland can be a legal threshold elsewhere, and a landlord's obligations differ accordingly.

When you need a certificate and how long it stays valid

EPCs are needed whenever a property is built, marketed for sale, or marketed for rent³. More precisely, they are only required when a dwelling is constructed, converted, sold or let¹⁰, and they must be provided when a building is advertised for sale or for let to a new tenant²⁵. It is the owner's or landlord's responsibility to make sure there is an EPC, to make it available to potential buyers or tenants, and to give a copy to the new owner when selling³. In Scotland, an EPC is required as part of the Home Report prepared for a sale, and the EPC must be provided to the purchaser free of charge, as a legal requirement²⁶. When a building is advertised for sale in Scotland, the EPC rating must be included in the property advertisement²⁶.

A certificate is valid if it was entered on the register no more than 10 years before the date it is made available, or until a newer EPC is produced and registered, whichever is earlier²⁷. Each EPC is valid for 10 years and can be used multiple times during that period³.

Two practical duties sit alongside the validity rules. It is a requirement under law that the EPC must be "affixed" to the building, and building standards guidance suggests the boiler or meter cupboard as a suitable place²⁹. And an estate or letting agent must legally show the EPC to anyone who makes an enquiry about a property, when they first ask about it⁸. Every certificate is lodged on a national register and can be accessed through the public search facility: for domestic dwellings in England and Wales at epcregister.com³⁰, with a separate register for Northern Ireland³¹. If you believe a certificate for a property is wrong, see who to contact about an EPC problem.

Assessment fees and why published prices vary

Assessments vary in price and are generally available from £35 to £100⁴. The cost of the EPC varies from one company to another, and depends on the size, location and age of the building, so householders are advised to shop around²⁷. There is no fixed national fee and no statutory price, which is why quotes for the same house can differ.

What the fee buys is the survey, the calculation and the lodgement of the certificate on the register. Once lodged, the document is public and free to retrieve for the rest of its validity, so the assessment is a one-off cost per certificate rather than a recurring charge. Two things are worth checking when comparing quotes: whether the quote includes the lodgement fee, and whether the assessor is accredited, since only an accredited assessor using an approved methodology can produce a valid certificate¹². The cheapest quote is not a bargain if the resulting certificate rests on assumptions you could have corrected with evidence, because the cost of a poor rating, in a lower sale price, a failed rental threshold or an unclaimed improvement, usually exceeds the difference in survey fees.

How your rating influences sales, rentals and upgrades

The rating has real weight in the housing market. Among prospective homebuyers surveyed, 39% stated that a property's EPC rating was a "very important" factor in their decision⁴. In Scotland the rating must appear in the advertisement when a building is marketed²⁶, and elsewhere in the UK the certificate is tied to minimum energy efficiency standards for rented homes in a way that Scotland's is not²⁴.

The certificate also opens doors to improvement funding. An EPC provides an assessment of a home's energy efficiency that is used when considering measures such as solar photovoltaic panels³², and grant schemes typically require a valid certificate as evidence of the property's starting point and of the measures it needs.

The improvement loop is where the certificate earns its keep for a household planning work. The recommendations report lists what the methodology believes is cost effective³; the householder carries out the work; a new assessment then records the improved fabric and heating and produces a higher score. Under the current system the old certificate stands until it is replaced, valid for 10 years regardless of any changes made to the property⁴, so the new survey is what converts physical improvement into a documented rating. Households that engage with this loop report acting on it: 65% of those who had seen the recommendations section said they had made changes based on it¹⁴.

What the certificate reveals and where it falls short

An EPC is a document about the building, not about the household in it. The assessment reflects the energy performance of the building itself, not the way it is used by its occupants⁵. That is both its strength and its limit. For a household working towards energy independence, the certificate is the best standardised picture available of the fabric: where heat is being lost, what the heating system is, and what the modelled costs and emissions are⁷. It is a baseline from which insulation, heating and generation decisions can be planned, and it is the document most grant schemes and policies recognise.

What it does not tell you is equally important to be clear about:

• It does not measure your actual consumption, because it standardises occupancy⁵.
• It does not verify the fabric, because its U-values are largely assumed from construction type and age⁶.
• Its cost figures are modelled on assumed energy prices⁴.
• Its rating rewards cheap-to-run heating over low-carbon heating¹⁵, so a home can carry a flattering band while depending entirely on gas, or an unflattering band while being close to self-sufficient.
• It says nothing about where your energy comes from, who supplies it, or how exposed the household is to price rises, which are the questions that actually define independence.

The system itself is being reworked, and a reader should know that the document in front of them is not the final form. The UK government is reforming EPCs by introducing new ratings, redesigning the certificates and improving the operational infrastructure²⁵; Scotland is introducing a new rating system covering fabric energy efficiency, heating system performance and the cost of energy to run the home to standardised conditions¹⁹, with a redesigned certificate to coincide with the new rating system¹³. Until those land, the practical position is this: the EPC is a useful, standardised, partly assumed snapshot of the building, and the household that treats it as a starting point to be verified, rather than a verdict, will get the most from it.

For the wider picture of where the EPC fits into managing a home's energy, see the home energy how-to guide.