A Guide to Window Energy Ratings

Launched in 2004 by an independent government supported body, Window Energy Ratings (WER) were established to develop and administer a system of UK energy ratings focussed solely on windows. The aim of the scheme was to make it easier for homeowners to understand how energy efficient their windows are and highlight how effective modern double glazing can be. 

Using a colourful, rainbow inspired design, which has been widely adopted on energy labels for popular home appliances, such as refrigerators and washing machines, the labels provide an easy way to see how different window products compare when it comes to their energy efficiency. 

The labels use an easy-to-read, traffic light system which includes a letter and colour band ranging from A++ to E. Just like your school grades, the higher the letter in the alphabet, the better your window is at doing its job. An A++ rated window is therefore far more energy efficient than a window with an E rating. Letter ratings are given to windows based on their thermal efficiency, air leakage and solar gain, and take into consideration the whole window, including the frame material, glass type, shape and design – as well as other components. As you would expect, the highest window rating is more likely to cost more, however while this may be a higher outgoing in the short-term, it is guaranteed to have long-term cost-effective benefits.

¹ Research found by Energy Saver, 2021