Have you ever seen the different stickers on the edge of a window and wondered: “What are they all?”. They’re all really important, but don’t worry, we’re here to help…

There are many different types of Window Energy Ratings. So let’s break down what they mean, and how you can make sure you’re getting the best for your money.

What is a Window Energy Rating?

Window Energy Ratings (WER) show you how energy-efficient your windows are. They tell you how well your windows prevent heat loss, absorb natural energy, and keep out draughts.

The rating system ranges from E to A++, with A++ being the most energy efficient. This means that the window is the best at keeping heat in, and excluding draughts – which keeps your home toasty, and your bills low.

The WER assesses a window based on three things:

• Heat loss – how much heat is the window letting out of your home
• Solar gain – how much heat travels through your window into your house
• Air leakage – the level of uncontrolled airflow out of the window, leading to heat loss

The window is then given a rating, helping you choose which windows are best for your home, and best for your budget.

Where did Window Energy Ratings come from?

The Window Energy Rating System was created by the British Fenestration Ratings Council in 2004, the most trusted window and door energy performance assessors in the UK (BFRC, 2025).

They set the standard that all manufacturers must meet in order for their windows to pass and adhere to the building regulations set by the government. The standard has improved a lot over the years, and today, windows must be rated B or above to pass.

But why are they important?

If a window doesn’t meet the BFRC standard, then they aren’t very efficient. They won’t keep the cold out and will likely lead to much higher energy bills (as you’ll have to keep putting the heating on!).

Any window below C rated are considered as “not efficient”. So if you’re looking into improving your home, and want to lower your energy bills, we recommend choosing windows that are rated B or above.

The Window Energy Rating is important, as it is a standardised measure that manufacturers can assess their windows against. This makes it much easier for homeowners to understand what they’re buying, and why it’s the best product for them.

Want more information?

You can find out more about Window Energy Ratings from the BFRC website, and contact us to find out which windows are best for your home.