EPC Ratings Explained

Energy is a bigger topic right now than it’s been in a generation. As the UK bids to work its way through an ongoing energy crisis, most of us have become more conscious of how much energy we use.

A big part of that is how well our homes perform in terms of how much energy they need in order to keep running effectively. Here we take an in-depth look at Energy Performance Certificate (EPC) ratings, what affects them, and what you can do to improve the efficiency of your home.


EPCs tell us how energy efficient buildings are, based on a rating from A to G - with A being the most efficient.

Similar to the stickers with multi-coloured bandings you see on appliances such as fridges, TVs and ovens, an EPC gives you an idea of how much energy it’ll take to heat and light your home, as well as what the likely carbon dioxide emissions will be. This means you can work out how much it ought to cost to run your home, while also informing you how environmentally-friendly it is.


When a new home is built or a house is put up for sale or rent, it must be rated for its energy efficiency. The government’s Standard Assessment Procedure (SAP) is a method for assessing and comparing how a property performs in terms of its energy and environmental impact.

Building regulations dictate that homebuilders obtain both design and as-built SAPs, which are generated by pulling together all of the build criteria including materials used, insulation and heating types.
A SAP calculator can provide a prediction for how energy efficient a house is going to be, before building work has even begun. When the property has been built, it undergoes a series of tests, including of the air, which produces an as-built EPC.


You need to get an EPC if you want to sell or rent out your home. The certificate must be made available to potential buyers and renters as soon as you put it on the market.

A domestic energy assessor can produce an EPC for you, this will be valid for 10 years from the date of issue.

You may also find it useful to get an EPC even if you’re not selling or renting your home, as it could point out a number of ways in which you can make your home more efficient, saving energy and money in the long run. 


There are numerous things that affect how efficient a building is, which is what the EPC rating is based on. Design SAPs focus on the air permeability of a property, aiming to reduce heat loss. Poor construction techniques and things such as windows that leak heat easily will bring down an EPC rating, while buildings that have an air permeability above 10 pascals must be improved to meet this minimum standard.
EPC ratings are heavily influenced by things such as the insulation a property has in its walls and roof, as well as the type of floor it has. The heating and hot water systems are also key, along with the lighting and types of bulb used. Having good, double-glazed windows will improve your EPC rating, along with things like having thermostats to make your heating system more intuitive.


New builds ought to perform very well when it comes to energy efficiency. EPC ratings should be strong, as modern building techniques and regulations are designed to be as environmentally and energy friendly as possible. As well as being more beneficial for the planet as we try to counter the effects of the climate crisis, this also translates directly into savings on your energy bills.

Around 84% of new build homes have an energy efficiency rating of A - B, while less than 4% of existing homes reach the same standard*. However, at Wain Homes, 100% of our new homes have an energy rating of ‘B’ or above, helping you to save money on your bills. You can read more about our the features of our energy efficient homes here.
It’s difficult to prove in terms of cold hard figures exactly what energy and monetary savings can be made when you live in a new build home, as every household uses energy differently and there are countless variables that come into play.
For more ideas on how you can save energy and money on your energy bills, read our blog on energy saving here.


We aim for an air permeability rating of 5 pascals when we design our homes, which is much better than the limit of 10. When our accredited air testers actually carry out their tests on our homes, the results will often come out around 3.5 pascals, showing how well our new builds perform in terms of energy efficiency.

We always aim to develop homes that are better than the base industry standard, meaning we go far above and beyond what the minimum spec needs to be in order to satisfy regulations.
With all of our homes achieving an energy rating of 'B' or above, you can look forward to lower energy bills. 

If you’re looking to buy a new home or have any questions about the home building or home buying process, get in touch with our team today. 
*HBF Energy report - Watt a save - Oct 2022