Energy Performance Certificates: What an EPC Measures

An Energy Performance Certificate is a standardised rating of a building's energy performance, produced by an accredited assessor and lodged on a national register. It rates a home on a scale of 1 to 100 and splits that score into bands A to G, with A the most efficient¹. It is required when a building is sold or let to a new tenant, and on completion of construction of a new building². It is valid for ten years³.

What it measures is narrower than most householders assume. The assessment reflects the energy performance of the building itself, not the way it is used by its occupants⁴. It is a modelled figure built from the fabric, the heating system and standardised assumptions about occupancy, climate and fuel prices, not a reading of the household's actual consumption. The Scottish Government describes EPCs as intended as a basic, standardised assessment and not a substitute for detailed, technical, retrofit assessment and advice⁵.

That distinction matters for energy independence. An EPC tells a household where the building sits against a fixed benchmark and what measures would move it. It does not tell the household what it spends, what it could generate, or how exposed it remains to a supplier, a grid connection or a fuel it does not control. The certificate is a starting point for fabric work, not a measure of self-sufficiency.

What an EPC is and what it measures

An EPC is a widely used measure of the energy performance of buildings, both in the residential and commercial sectors⁸. It provides information about the energy efficiency and emissions of a building, and it comes with information on measures which could be made to improve the energy efficiency of the building, plus an indicative cost for each improvement⁴.

The certificate carries two headline ratings. Both the energy efficiency rating and the environmental impact rating are scored on a scale of 1 to 100 and split into bands A to G¹. The energy efficiency rating is the one that carries legal weight: it is the only metric currently used in government policies targeting domestic buildings⁸. That single fact explains much of the criticism the certificate attracts, because a policy instrument built on one number will be judged on whether that number drives the right decisions.

A home rated EPC C or above is generally regarded as having an adequate level of energy efficiency⁹. That is a working threshold rather than a statement about comfort or bills. A Band C home can still be expensive to run if it is large, poorly used or heated by a costly fuel, and a Band D home with a well-matched heating system can cost less than a Band C home with an oversized one.

For a household thinking about independence, the certificate's value is diagnostic. It identifies the fabric and system measures that would raise the modelled rating, and it does so in a form that lenders, landlords and grant schemes recognise. It does not measure how much of the household's energy comes from its own roof, its own wood, or its own decisions.

The rating scale: 1 to 100 points, bands A to G

The scale runs from 1 to 100, though the underlying SAP score is described as a 1-100+ score presented on a distinctive graphic which shows how the score maps onto seven rating bands represented by the letters A-G¹⁰. In practice, published statistics describe the EPC score as typically ranging from 1 to 100⁶.

The band boundaries are not evenly spaced, and the lower bands are narrow. Band G covers 1 to 20, the least efficient, and Band E covers 39 to 54⁶. A home sitting at the top of Band E is a short step from Band D; a home at the bottom of Band G needs substantial work before it reaches the rental minimum.

The certificate shows a current rating and a potential rating. The gap between them is the modelled effect of the measures in the recommendation report, and it is the part of the document most useful to a household planning fabric work. A large gap usually points to insulation, glazing or heating controls rather than to behaviour.

How the rating is calculated: SAP and RdSAP

To determine the energy efficiency rating of a home, EPC assessors use the standard assessment procedure, known as SAP¹. SAP stands for the Standard Assessment Procedure for Energy Rating of Dwellings, and it supports the production of EPCs¹¹. The content of the domestic EPC is produced by calculations carried out in the SAP methodology⁸.

For existing homes, where full construction information is often unavailable, assessors use a reduced version. The methodology is standard assessment procedure for new and existing dwellings, with reduced SAP, RdSAP, applied to existing homes where information may not be available¹. RdSAP is the reason two superficially similar houses can score differently: where a wall type, insulation thickness or glazing specification cannot be established, the software falls back on defaults drawn from the age and type of the building.

That defaulting is the mechanism behind most disputes about accuracy. An assessor who cannot see inside a cavity wall, under a floor or behind a dry lining will record what the convention assumes for that construction and era. The resulting score is reproducible and comparable across the stock, which is what a policy instrument needs, but it is not a measurement of that particular house.

The Scottish Government has consulted on not treating EPCs as a substitute for a more detailed or specialist retrofit advice or technical survey, such as assessment following PAS 2030 or PAS 2035¹². That position is consistent across administrations: the certificate is a screening tool, and a whole-house retrofit plan sits above it. Households planning fabric work at scale will get more from a whole-house retrofit plan than from the certificate alone.

What the certificate contains, including the recommendation report

An EPC should contain a minimum set of items: the building asset rating against a benchmark, a recommendation report, the reference number and date of issuance, the building address, and the building's total useful floor area⁴. It also carries information on potential energy costs and carbon dioxide emissions, with a coloured chart showing how energy efficient the building is or could be¹³.

The recommendation report is the substantive part for a household. It provides more detailed information about improvement measures, and it outlines the recommended measures that can be taken to improve the energy rating⁴. Cost effective recommendations to improve the energy efficiency of the building are included with the certificate¹⁵.

The legal basis for the report is long-standing. Under the Northern Ireland energy performance of buildings regulations, the certificate shall be accompanied by a recommendation report¹⁶. In Wales, the approved document amendments require the certificate to include a recommendation report unless there is no reasonable potential for energy performance improvements¹⁷. Where a report is included in an energy performance certificate, its validity runs for ten years from the date of that certificate¹⁸.

That advisory status is worth holding onto. The measures listed are the ones the software associates with a rating improvement for that building type, not a surveyor's judgement about what that particular house needs first. A household acting on the report should expect to have the measures specified properly before work starts, and the fabric pages on this site set out what each measure involves: loft insulation, cavity wall insulation and solid wall insulation each carry their own conditions and risks.

What an EPC does not cover

The certificate is deliberately bounded, and the boundaries are stated in official guidance. The EPC assessment reflects the energy performance of the building itself, not the way it is used by its occupants⁴. A household that heats one room, runs a heat pump on a smart tariff or generates its own electricity will not see that reflected in the rating.

It does not contain personal information, other than the name and contact details of the assessor who carried it out⁴. It is not a condition survey, a structural report, a damp survey or an electrical certificate. It does not record appliance efficiency, hot water cylinder insulation in isolation, or the state of the heating system beyond its type, fuel and controls.

For non-domestic buildings, the EPC shows an asset rating, alongside an indication of energy performance based on primary energy use⁴. Domestic certificates work differently, and the Scottish consultation on reform focused on domestic EPCs and did not include non-domestic EPCs¹².

Coverage of the stock is incomplete, which limits what any single certificate can be compared against. Around a third of domestic properties in England and Wales do not have an EPC rating¹⁹. EPCs cover around 60% of the housing stock in England and around 55% in Wales, based on Census 2021 analysis by the ONS³. A household comparing its score with a national average is comparing against a partial sample, weighted towards homes that have changed hands or tenancy.

Validity: 10 years, and when you need a new one

An EPC is valid for a maximum of ten years, or until another EPC is commissioned for the same building, whichever is sooner²⁰. Each EPC is valid for 10 years and can be used multiple times during that period¹³. Ratings are valid for 10 years²¹, and the same ten-year figure appears in the boiler upgrade scheme guidance, which requires an EPC that is no more than 10 years old²².

The trigger for a new certificate is a transaction, not the passage of time. A new EPC does not need to be produced when the previous certificate's ten-year validity period expires, unless the property is being sold or let to a new tenant²⁰. EPCs do not have to be provided where an existing tenant is renewing their lease²⁰. A household staying put does not need to renew anything.

Where a certificate is needed, the obligations are specific. An EPC is required when selling or letting an existing building². EPCs must be provided when a building is advertised for sale or for let to a new tenant, and they are also required upon completion of construction of a new building²³. They must be displayed by certain large non-domestic buildings²³.

For buildings for sale, the EPC must be provided to the purchaser, free of charge, and this is a legal requirement²⁴. When a building is advertised for sale, the EPC rating must be included in the property advertisement²⁴. Where there is not enough space to include the colour coded chart energy indicator, the EPC energy rating must be stated, for example EPC F36¹⁵.

The Scottish Government has consulted on a reduction of the validity period of EPCs from 10 to five years to ensure consumers have more up-to-date information²⁵. That proposal has not replaced the ten-year rule. Reform consultations point to shorter validity, while the operative guidance continues to state ten years²⁰.

Minimum ratings for rental homes and the road to Band C

The current legal floor for domestic private rented property in England and Wales is Band E or above⁷. The legal basis is the 2018 Minimum Level of Energy Efficiency standard, which set EPC band E for domestic, private rented property¹⁴. Landlords of domestic private rented properties, including public sector landlords, may not grant a tenancy to new or existing tenants if the property has an EPC rating of band F or G, unless an exemption applies⁷. Landlords must not continue letting a domestic property that is already let if that property has an EPC rating of band F or G, unless an exemption applies⁷.

Where a property is let with a rating of F or G, it must be improved to a minimum rating of E or an exemption registered where applicable¹⁴. The exemption route matters for older and harder-to-treat homes, and the conditions attached to it are set out in the MEES guidance for rented homes.

The next step is proposed rather than in force. The UK Government has proposed raising the minimum EPC standard for domestic private rented properties to band C by 2030⁷. That is a proposal, and it should be read as such until the regulations are made.

The four nations diverge here. England and Wales operate the Band E minimum through the 2018 standard¹⁴. Scotland has consulted separately on energy efficiency standards for the domestic private rented sector, with proposals that would extend to all private rented sector properties by the end of 2033 if passed as proposed²⁶. Northern Ireland's requirements sit in its own energy performance of buildings regulations¹⁶. A landlord with property in more than one nation is dealing with more than one regime.

How homes across the UK actually rate today

The most recent published figures give a clear picture of the existing stock. Homes in England had a median Energy Performance Certificate score of 69, Band C, as of March 2025⁶. That median conceals a wide spread, and the spread is where the policy problem sits.

New build performance is markedly different from existing stock. In England, in the quarter January to March 2026, 87% of new dwellings were given an A or B rating, an increase from 86% in the same quarter a year earlier³. Most new dwellings, 67%, were given a B energy efficiency rating³. Existing dwellings were more likely to be given a C or D rating, at 88%, compared with 12% of new dwellings³.

Wales shows a similar pattern with a different distribution. In the quarter January to March 2026, 92% of new domestic properties received an energy efficiency rating of A, the highest band³. The majority of new dwellings in Wales, 55%, were given an A rating³.

Tenure matters as much as age. Around two-thirds of Council or Housing Association houses have EPC ratings A to C, compared to around 40% of houses in other tenure types¹⁹. Age compounds it: around a quarter of gas consuming properties built before 1945 have EPC ratings A to C, compared with around 95% among newer properties¹⁹.

Activity across the register is substantial. In the quarter January to March 2026, 460,000 EPCs were lodged on the register in England and Wales, domestic and non-domestic, a 2% decrease compared to the same quarter in 2025³. Over the 12 months to March 2026, 1,649,000 domestic EPCs were lodged in England, a 4% increase on the previous 12 months³. The regional picture is uneven: the largest increase in EPCs lodged for new dwellings compared with the same quarter in 2025 was in London, and the largest decrease was in the North West³.

For a household, the useful comparison is with homes of the same age, type and tenure, not with the national median. The energy efficiency of the UK housing stock sets out how the stock divides by era and construction.

Limitations of the EPC as a measure of real energy use

The certificate's own authors are candid about its limits. The ratings on EPCs are an important policy tool, used to define standards and targets for reducing emissions from homes, but poorly suited to this role²⁷. The Climate Change Committee states that the current EPC rating metrics do not accurately incentivise the energy efficiency and heating solutions required to deliver Net Zero homes²⁷.

The most cited example is the treatment of heat pumps. Replacing a gas boiler with a heat pump can, in fact, reduce a property's EPC score, which can negatively impact the property's value²⁸. That outcome follows from a metric built on running cost and primary energy under standardised assumptions, where gas has historically compared favourably with direct electric heating. A household that electrifies its heat and improves its fabric can see the fabric gain partly offset by the fuel switch.

The Energy Cost Rating proposed in reform work is intended to address part of this. It will be based on the cost of energy to run the dwelling to standardised conditions, modelled based on UK-wide fuel cost factors and normalised climate data, showing a current and potential rating⁵. That is a modelled cost, not a bill, and it will move when fuel price assumptions move.

Reform is under way. The stated intention is to reform EPCs by introducing new ratings, redesigning the certificates, and improvements to the operational infrastructure²³. Until those changes take effect, the certificate in force is the one described here, and its limits are the ones a household should plan around. For fabric measures that raise a rating and reduce real demand, the guide to improving an EPC rating sets out the order of works.