How to get an Energy Performance Certificate you can trust

Energy Performance Certificates (EPCs) were designed as a simple way to compare the energy use of different properties when buying or renting a home. 

They give homes a rating between A (very efficient) and G (inefficient) and recommend the most cost-effective ways to improve energy efficiency. 

However, a Which? investigation into EPC accuracy in 2024 found that many EPCs aren't nearly as useful as they should be, as they can be inaccurate and unhelpful. 

We’ve put together this guide to explain everything you need to know about EPCs, how to understand them, and what to do if your EPC is wrong. 

For tips on how to improve your rating, head to our advice on how to make your home more energy efficient. 

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How to get an EPC

If your home already has an EPC, it should help you identify possible improvements. Your property is likely to have an EPC if it has been marketed for sale or rent since 2008.  

You can find any current or expired EPC for a home in England, Wales, or Northern Ireland on the government’s EPC Register or, in Scotland, on the Scottish EPC Register. 

EPCs are valid for ten years, so yours may have expired. If you have made changes to your home since the date of the EPC assessment, it may no longer be accurate.

If your home doesn’t have an up-to-date EPC, you can get one for around £60-£120, depending on its size and location. 

To book a new EPC assessment, contact a qualified Domestic Energy Assessor to make an appointment. An assessor will come to your home to carry out an assessment and then generate your report. 

You can find an assessor through the EPC Register in England, Wales or Northern Ireland or the Scottish EPC Register in Scotland.

How to understand your EPC

Once you receive your EPC, it's worth reading through it to ensure its accuracy and consider what you can do with the information it contains. 

An EPC is made up of several sections that each contain important information about your home.

We’ve used example snapshots from different EPCs to explain what to look out for in each section.

Note that EPCs in Scotland look a little different from the examples shown below, but the information contained is very similar.

Here's how to check that yours is correct:

1. Property description

The first section includes the property address, type, and total floor area, plus the overall energy rating, certificate number, and expiry date.

It may seem basic, but you should always check this is correct. 

It’s not unknown for the address to be recorded incorrectly – especially if your home has a name or a flat number instead of, or as well as, a street number – which may cause confusion if it doesn’t match official documents.  

A misdescription of the property type or an incorrect floor area can significantly affect the calculations that generate the energy rating. If the property has been advertised for sale or rent, check the floor area against a previous EPC or property description; a small difference is to be expected, but you should query a significant mismatch.

If it is more than 10 years old, the EPC will have expired, and a warning symbol and message appears at the top. There's no requirement to get a new one, unless you want to sell or let your home.

2. Energy rating and score

The energy rating graph is the part of the EPC that most homeowners are familiar with. It shows the current rating and score, plus the potential rating and score you could achieve if the recommended improvements are made.

The energy rating band (A to G) is what is often referred to as the EPC rating. The numerical score is the number of SAP (Standard Assessment Procedure) points calculated for the property. 

It can be helpful to see where your home sits within the energy rating band; this property, for example, is in the top half of band E. Just five more SAP points would take it into band D, so there may be an inexpensive upgrade that could move it up a band.

The energy rating is calculated based on how much the home will cost to run. The lower the rating, the more it will cost to supply heating, hot water and lighting to the property. 

Gas is the cheapest heating fuel available, so gas boilers tend to receive the highest ratings. That means that a poorly insulated home with a gas boiler is likely to receive a higher rating than a similar home with electric heating - even a heat pump.

This has led to some unintended consequences when it comes to the recommendations generated by an EPC report. Switching from a gas boiler to an electric heat pump can be a good choice from an environmental point of view, as it reduces carbon emissions, but it is unlikely to improve an EPC energy rating because electricity is more expensive than gas. Therefore, current EPC recommendations never include switching to a heat pump.

3. Property features

This section lists the main elements that contribute to the property’s energy efficiency and consumption. It includes the building 'envelope' (walls, roof, windows, floor) plus heating, hot water and lighting.

This section is one of the most important to check for accuracy. There are some useful points to note:

Assumed – This doesn’t mean the assessor has simply assumed or guessed whether there is insulation or not. It is a default selected according to the age of the building. 

For example, a Victorian-era home is assumed to have 'as built' solid brick walls with no insulation unless there is good evidence that insulation has been installed later. 

In more modern properties and extensions, where insulation is assumed to be present, the depth or thickness is based on the requirements of the building regulations that were in force at the time of construction. 

An EPC assessment is non-invasive, so no holes are drilled, or cavities opened up for inspection. That means assumed ratings are used when the assessor is unable to inspect an area or feature. However, if you have documentation and/or photos that show the installation of insulation or other relevant building works, this can be taken into account by the assessor.

Typical areas that are difficult to inspect and may be incorrectly 'assumed' include floor insulation, internal wall insulation, flat roof insulation and, if there is no loft access, loft insulation. If your home has had any of these fitted, make sure you retain the documentary evidence for any future EPC assessment.

Ratings – The ratings (from very good to very poor) are based on the energy efficiency characteristics of the feature. In the example above, the ‘fully double glazed’ windows are rated as ‘average’ due to their age and type; newer double glazing would likely receive a better rating. 

However, these ratings don’t consider the state of repair or how well features work. An EPC assessment is not a condition survey, and therefore, defects such as a broken window or incorrectly installed boiler will not be mentioned or factored into the calculations.

Although the ratings may seem quite crude, the data used to produce the energy rating is much more complex. A heating boiler is rated according to the efficiency of the specific make and model. For walls, floors, roofs and windows, the software calculates a U-value (the rate of heat transfer) for each feature and uses this together with the measured dimensions to calculate overall heat loss and energy use. 

The software records more than 140 pieces of data, but only a simple summary appears on the EPC.

Some other common areas of confusion include:

• No mention of loft - If you have loft insulation, it will be noted as part of the roof, and the word 'loft' may not appear. For example, it may say 'Roof - Pitched, insulated (assumed)', so don't be concerned that your loft insulation has been forgotten just because the loft is not specifically mentioned.
• More than one wall, floor or roof- If your home has been extended or improved over the years, your EPC may list more than one type of wall, roof or floor. The example above lists 'roof’ twice:
  • Pitched, no insulation (assumed) refers to the original pitched roof, which has not been converted or insulated since it was built.
  • Roof room(s), insulated (assumed) refers to the area of the roof that has been converted to living space – more commonly called a loft conversion – which was insulated at the time of the conversion.
• Lighting - The rating for lighting is based only on fixed outlets - that is, permanently wired-in fittings such as ceiling and wall lights - so you'll need low-energy bulbs in all of those to achieve the highest rating. The assessment does not consider any plug-in lighting, like table lamps and floor lamps.

4. Low and zero carbon energy

This section lists any low- or zero-carbon energy sources installed in your home. If you have solar PV panels, solar water heating, a heat pump, biomass heating, or a wind turbine, check they are listed here. 

5. Primary energy use

Primary energy use is a measure of the total energy used to produce power for the property. The calculation includes power station efficiency for electricity and the energy used to produce fuel and deliver it to the property.

You can safely ignore the primary energy use section, as it has no effect on the overall rating.

6. How this affects your energy bills

This is potentially one of the most important sections of the EPC for householders but it can appear misleading. It includes three key pieces of information:

1. The amount an average household would need to spend per year on heating, hot water and lighting in this particular property.
2. The amount you could save per year if you complete the suggested recommendations for improving the property’s energy rating.
3. The estimated energy needed in this property, in kWh per year, for heating and hot water.

These predictions are based on a theoretical typical household - not on measured energy use, nor on the household currently in residence.

The predicted energy use and costs are calculated using 'standard occupancy' so that homes can be compared on a like-for-like basis. 

Standard occupancy assumes the size of the household according to the number of bedrooms - which affects the predicted hot water consumption - and assumes a fixed heating pattern and thermostat temperature.

Depending on the size of your household and your lifestyle, your own energy consumption and bills may differ quite significantly from the EPC figures. This doesn't mean the EPC is incorrect - just that your household's energy use is not the same as the typical household.

Costs quoted are based on typical energy costs at the time the EPC is issued. If you're looking at an EPC that's a few years old, the costs are likely to be out of date.

Furthermore, the EPC only considers heating, hot water and fixed lighting, ignoring energy use from kitchen appliances, TVs, computers and any other energy-using devices in your home.

Read more about: 10 ways to cut down your energy bills

7. Impact on the environment

Each property gets a rating from A (best) to G (worst) depending on how much carbon dioxide (CO2) is emitted each year from the use of fuel for heating, hot water and lighting. 

Again, there are three key pieces of information:

1. Annual carbon emissions from an average household
2. Annual carbon emissions from this property
3. Potential annual carbon emissions from this property

The 'average household' here is an average across the UK, for comparison purposes.

The annual carbon emissions from the property are related to the energy efficiency rating, but are also highly dependent on the fuel type. Fossil fuels such as gas, oil and LPG produce more carbon emissions than electricity, so switching to electric heating will improve the environmental impact rating. Low and zero carbon energy sources will also improve this rating.

It is possible to receive very different ratings for energy efficiency and environmental impact. An older home with uninsulated solid walls and floors and adequately insulated roofs and windows may get an average-to-poor rating for energy efficiency (a D or E), but if it has a low or zero carbon heating system, solar PV and water heating panels, it could receive an A or B rating for its low carbon emissions. 

When considering home improvements, it's important to be clear about your goals. Some retrofit measures make more difference to energy efficiency or costs, while others are better for the environment.

If you are considering greener options, head to our guides on heat pumps explained and our buying advice for solar panels. 

8. Changes you could make

This section lists the recommended changes you can make to improve your home's energy efficiency in the preferred order you should make them.

The recommendations are generated automatically by the EPC software. There can be many recommendations, but the assessor can suppress them, so you'll often see just the top three or four.

Each recommendation has a short description - for example, Step 1: Increase loft insulation to 270 mm - followed by the typical installation cost, typical yearly savings, and potential energy efficiency rating on completion.

Installation costs are shown as a broad range and are not calculated based on the individual property. You'll need to contact installers to get a more accurate quote for any recommended work.

The annual savings are based on the property, though, so you should get an idea of whether it's worthwhile doing the work in terms of energy bill savings.

The quoted costs and savings are based on average costs at the time the EPC is issued. If you're looking at an EPC that's a few years old, the costs are likely to be out of date.

The improvement in energy efficiency rating builds as you complete each step, so you'll need to follow each recommendation in turn to achieve the final potential rating.

Even if you don't plan to carry out any work immediately, it's worth checking these recommendations for accuracy. For example, if your EPC recommends solar PV panels, but you already have them, then it's likely they have been missed off your report and you should check the rest of the EPC to see if they are mentioned.

About your certificate

The final sections of the EPC indicate the date of the assessment and the date the certificate was issued, contact details for the assessor who issued it and the assessor's accreditation scheme.  

Finally, it lists any other EPCs for the same address. These are worth reviewing, as it can help you spot inaccuracies. 

If there have been no significant changes to the property since the previous assessment, then the EPC should be almost identical. Calculations and ratings may change slightly, due to changes to the underlying methodology and software, but fundamentals such as the property type, floor area and descriptions of property features should be consistent. 

If insulation or features listed on a previous certificate have not been mentioned subsequently, it's worth checking with the assessor as they may have been missed. 

How accurate are EPCs? Our research explained

It’s tricky to identify inaccurate ratings on individual EPCs. Homeowners have no access to the data input to generate a certificate and often lack the expert knowledge to spot incorrect results.

However, academic researchers have found a high likelihood of errors in EPCs. In 2019, researchers at Leeds Beckett University found issues with 27% of EPCs that suggest they are incorrect.

Also, in 2019, research from UCL Energy Institute at University College London found evidence that measurement errors compromise the reliability of EPCs, resulting in homes being rated in the wrong EPC band.

Our EPC research

In February-March 2024, we selected 12 Which? members to participate in mystery shopping research and have an energy assessment carried out at their homes.

The results uncovered issues with both the accuracy of the results and the recommended improvements.

One homeowner never received their certificate. The assessment fee was refunded, but the homeowner was left none the wiser about their home's energy efficiency.

Of the remaining 11 participants, just one was ‘very satisfied’ with their EPC. Only three said they were likely to recommend getting an EPC based on this experience.

Eight out of 11 told us their EPC did not appear to be accurate, and some participants also felt that the recommendations made were unaffordable and would not achieve significant savings.

Errors on EPCs

When we examined the EPCs in detail, we found inaccuracies regarding insulation, heating, and solar panels.

One EPC had very significant errors, which we pointed out to the assessor. He subsequently made corrections and issued a new EPC, with the energy efficiency rating jumping up two bands, from D to B.

These anomalies were fairly easy to spot because features were clearly misdescribed or omitted altogether.

But for many homeowners, it’s hard to know if an EPC is correct because they never see the information that is input – only the limited outputs on the certificate.

Frequently asked questions

What is an EPC?

Energy Performance Certificates (EPCs) were designed to be a simple way for people to compare home energy efficiency.

They were introduced in 2007 as part of the Home Information Pack (HIP) to help prospective buyers compare the energy use and environmental impact of different properties. 

Although the requirement for a HIP was later scrapped, a valid EPC is still needed when selling or letting a home.

They give homes a rating between A (very efficient) and G (inefficient) and recommend the most cost-effective ways to improve energy efficiency.

In recent years, they have been used in a much wider context than originally intended. EPC ratings now play an important role in government policies aimed at decarbonising homes and delivering Net Zero.  

Why do you need an EPC?

A valid EPC must be available when a home is marketed for sale or rent; however, EPCs are valid for 10 years from the date of issue, so you may not always see a very recent one in a sales or lettings ad.

Landlords can’t legally rent out properties with the worst energy efficiency ratings (F or G). Some home improvement grants may only be available if you have a valid EPC above or below a particular energy efficiency rating.

An increasing number of ‘green’ finance products, including mortgages, are also subject to meeting specific EPC requirements.

If you’re hoping to cut your energy bills or reduce your environmental impact, an EPC can help you understand where improvements can be made and will recommend options to improve your home’s energy efficiency.

Where can you find your EPC?

Unless you're advertising your home for sale or rent, EPCs are not compulsory, and not every home has one. 

Currently, around 65% of UK homes have had at least one EPC, but if your home has not been sold or rented out since 2007, it’s less likely to have one. 

All EPCs are lodged in an online database where anyone can view them. You can find any current or expired EPC by searching using your address and postcode. 

For addresses in England, Wales and Northern Ireland, go to the gov.uk EPC Register or for addresses in Scotland, go to the Scottish EPC register. 

How much does an EPC cost?

The price of an EPC is not fixed, so each assessor can set their own rates. 

When carrying out our research in February-March 2024, we paid between £47 and £85, but prices can be much higher so it pays to shop around.

As you might expect, prices for large properties are generally higher than for smaller ones due to the extra time needed to carry out the assessment. You may also have to pay more if you live in a remote or rural area since the assessor may have to factor in considerable travelling time.

How to find an EPC surveyor

Only qualified Domestic Energy Assessors (DEAs) can produce EPCs for homes. Although some large surveying firms offer EPC assessments, most DEAs are self-employed.

For homes in England, Wales or Northern Ireland, you can find your nearest accredited assessor here. For homes in Scotland, you can find an EPC assessor here.  

These official listings show the assessor's name, contact details and accreditation but give no indication of prices or customer reviews. To book an assessment, homeowners must contact DEAs individually to request a quote.

Alternatively, there are websites where assessors can be booked online, such as energyperformancecertificates.co.uk, theepcregister.co.uk, and myconstructor.co.uk. These often display prices, availability and ratings from previous customers.

Always check that your assessor is an accredited DEA before agreeing to an assessment.

What if your EPC is not accurate?

All Domestic Energy Assessors (DEAs) must join an approved accreditation scheme through which they submit (or ‘lodge’) each EPC.

The accreditation schemes oversee the DEAs and are required to audit at least 2% of all EPCs lodged.

Every EPC includes the name and contact information of the assessor who carried out the survey and the accreditation scheme they were registered with and through which they lodged the certificate.

If you believe your EPC is inaccurate, you should first contact the DEA and discuss your concerns with them. If there is a mistake, they should correct it and issue a new EPC at no extra cost.

If you are unable to resolve the matter with your assessor, you should contact the accreditation scheme shown on the EPC to make a complaint.