What is an Energy Performance Certificate (EPC)?

Much like the multi-coloured sticker found on your new fridge freezer or similar appliance, an Energy Performance Certificate (EPC) provides an Energy Efficiency (EE) rating for a building by applying a scale between 1-100 from G (very inefficient) to A (very efficient). Using the same scale, it also provides an Environmental Impact (EI) rating for carbon emissions. The EE and EI ratings are calculated using a national calculation methodology which is based on information such as building fabric materials, insulation performance, construction details, heating, ventilation and cooling systems and solar gains. The EPC provides the building owner, or would-be buyers and tenants, with insights into possible measures to improve the energy performance and the estimated cost of running the building. Figure 1 (right) visualises how the ratings are shown on the EPC with the potential rating highlighting what rating could be achieved if the improvement measures are installed. 

EPCs can be produced for both domestic and non-domestic buildings as well as for new and existing buildings. It is a legal requirement as soon as you start to market your property for selling or renting. In Scotland, EPCs can only be produced by an accredited EPC assessor who is a member of an ‘Approved Organisation’ and an issued EPC is valid for 10 years. Energy Saving Trust (EST) provies a list of approved assessors and organisations. 

Why is an EPC important?

In most EU countries, including the UK, EPCs have been legally introduced as part of EU Directive 2002/91 on the Energy Performance of Buildings (EPBD). This has been done to track the energy performance and consumption of buildings across Europe responsible for 36% of carbon emissions and 40% of the energy consumed across Europe.  

Benefits of an EPC for a homeowner

Your EPC will indicate how much it will cost to heat and power your building. The EPC also recommends the most suitable improvement measures for the given building, as well as whether you can potentially access funding to install these measures. For a domestic EPC, details are listed on potential savings that could be made should you improve the energy efficiency of your property (illustrated in figure 2 below). Also, property tends to increase in value with higher EPC ratings as highlighted in a Department for Energy and Climate Change (now Business, Energy and Industrial Strategy) study. This is useful when looking to sell or let. 

Figure 2. Example of estimated energy costs and potential improvement savings

Reliability of EPCs

Changeworks’ experience, as well as industry research, has highlighted that the accuracy of EPCs varies. This poses serious implications for legislation and how we measure energy and carbon savings from energy efficiency improvements. Achieving a high EE rating on an EPC doesn’t necessarily equate to optimum low energy consumption and carbon reduction in practice. This has been attributed to many factors such as limitations and assumptions in the national calculation methodology, out of date information on volatile fuel prices and poor practice, all contributing to EPC inconsistencies and inaccuracies. Therefore, it is best to view the estimations provided in the EPC with this in mind. For example, an EPC gives a rough idea of energy bills, but it should not be viewed as an accurate picture for how much your energy bills will be. This is due to the limitations noted above and also the fact that tenant behaviour isn’t factored into the calculation.

To round up

EPCs and the rating systems applied are a useful benchmark to determine how much it may cost to heat and power your building and can be used to promote your building when looking to sell or let. It provides useful information with regards to the most suitable improvement measures, access to funding and potential running costs. However, it is evident there are inconsistencies and inaccuracies with the methodology and process for calculating an EPC rating. Therefore, to query any information on your EPC, householders should contact the energy assessor who produced the EPC (name and contact details are provided on the EPC). It is also worth checking the issue date on the EPC, as it is more likely that an EPC issued within the last few years will be the most accurate. For social landlords, Changeworks can provide support from reviewing and analysing the robustness of EPC data for your housing stock to being accredited and able to carry out a small number of EPCs. 

If you are a social landlord, get in touch to see how our consultancy services can provide support with EPCs.  


Gary Pearson, Surveyor and Data Analyst, Changeworks


Updated: August 15 2019