Window Energy Ratings: A, B, C Rated Windows Guide

11 February 2020
Updated 20 April 2023

You may think that by installing double glazed windows into your home means that your house will be warmer for longer, heating bills will be reduced and the value of your home will rise.

But this isn’t always the case.

Many homeowners don’t know that there are window energy ratings for different types of double glazing. 

And in this guide, we want to tell you everything you need to know about energy-efficient windows, what the difference between A Rated windows and B Rated windows is and what the overall impact these have on your home.

We’ll be looking at;

  • Window Energy Ratings
    • A Rated Windows Explained
    • B Rated Windows Explained
    • C Rated Windows Explained
    • Other Ratings
  • What Impact Do Energy Efficient Windows Have?
  • How To Choose The Best Windows For Your Home

We’ll also answer some of the more frequently asked questions at the end of our article so that you can start shopping around for the perfect windows for your budget and your home.

Window Energy Ratings (WER)

So what are window energy ratings?

Provided by the BFRC, it’s a colourful, easy to read label that showcases the overall energy efficiency of a complete window, from the frame to the glass on how well the window performs.

Window Energy Ratings Label Showing A Rated Windows, B Rated and C Rated Windows.

The performance of the window takes into account a number of factors including heat loss, solar gain and air leakage, together this creates how the information is displayed through the BFRC energy rating label as pictured above.

And what was once a nice to have in heat retention and lowering energy bills per month has become a necessity, it’s now become a legal requirement. 

So what do the ratings actually mean? 

A Rated Windows Explained

Quite simply, the higher the rating, the better the overall performance of the window. So if you have a higher budget and you’re willing to invest in A Rated or A+ Rated windows, then you will be receiving the highest energy-efficient windows on the market. 

But there is a trade-off between how much money you want to spend installing your windows versus how much money you think you may potentially save in the long run. 

Homeowners with disposable income may not have this worry and can afford to install the best of the best. 

But for homeowners who are cautious about their spend, but also want to invest and save money down the line, B Rated windows might be a better choice.

B Rated Windows Explained

Whilst still receiving most of the energy-saving benefits A Rated windows have to offer, B Rated windows offer slightly less in terms of an overall return on investment.

The only real difference for B Rated windows is they’re not as high-performing as A Rated windows are and they’re slightly cheaper to buy and install up-front.

This is why B Rated windows are a great option for more cautious homeowners. 

Ones who have the money to spend on new windows for their home, but don’t want to go overboard with their spending and find that B Rated windows offer everything they need in terms of spend versus cutting energy costs.

It mostly comes down to short term versus long term. 

In the short term, there is a higher up-front cost in order to receive and install A Rated or B Rated windows into the property, but the long term is how much impact those windows will have in reducing energy bills, promoting heat retention and boosting sustainability and energy efficiency throughout the house.

C Rated Windows Explained

For homeowners who are on a more tighter budget but want to upgrade their double glazed windows to something better that can reduce energy costs, C Rated windows might be the best option.

Whilst the difference between B Rated and C Rated is a closer gap than A Rated to C Rated, so too is the outcome from these windows.

The cost of energy bills may not be reduced as greatly as A Rated windows and heat loss may become more of a factor the lower down the window energy rating scale you get, but take into account the up-front cost for C Rated windows would be considerably much lower. 

That’s why with C Rated windows, they take into account budget. Receiving some of the energy-saving benefits at a more budget-level price.

Other Ratings

The lower down the window energy rating label you go, the less energy efficient the windows start to become and perform less.

That’s why we would highly recommend staying above the C Rated windows if your budget allows you to do so. 

We understand there is a trade-off between up-front costs and overall energy-saving benefits. But to go lower than C Rated windows, especially for an upgrade would potentially not be worth the investment due to not seeing any positive energy impacts for heat retention within the home.

However, this is purely our advice and each situation and homeowner is different. Please proceed with caution before investing in any double glazing windows and be sure to gather your research beforehand, to make an informed decision.

What Impact Do Energy Efficient Windows Have?

Energy-efficient windows have a huge impact on sustainability and promoting heat retention throughout the home.

If you’re upgrading from single glazed windows to A Rated double glazing windows, you will notice the difference almost instantly, as your property will be much warmer, will stay warmer for longer and energy bills will be greatly reduced. 

So are they worth the investment?

It depends on many different factors, your budget, the type of property you want to install double glazed windows in and what windows you currently have.

But from an energy-saving perspective with double glazing lasting up to 25 years, we would say that they are worth the investment and should be treated as such.

We’ve already established that the up-front costs may be quite high depending on the energy rating you choose to go for, but overall the return on your investment would mean saving hundreds of pounds a year and having a warmer more sustainable home in the long run.

Choose The Best Windows For Your Home

We hope you have a clearer idea of what to look for when buying double glazed windows. 

Whilst the window energy rating system is one part of the double glazing process, there are many other factors to consider when choosing the right windows. 

The style and design of the windows, the product quality and of course finding the best price for the windows you want.

By having an idea of the type of energy rating you’re looking for in windows can help determine which windows you may be interested in and in turn will show how much you may save in the long run and how much you might be quoted for up-front for the initial installation.

Find an installer near you to get quotes for free and with no obligation from our network of double glazing installers. Alternatively, use our QuoteBuilding tool where you can design online to your own specifications, the types of windows you want in your home and at the end, receive a free quote.

Frequently Asked Questions (FAQ)

What is an A Rated window?

An A Rated window is one of the best performing windows on the market in terms of energy efficiency, heat retention and overall performance. A Rated windows help cut energy bills and can help keep heat in the home for longer.

What type of window is most energy efficient?

The higher up the window energy rating (WER) label you go, the more energy efficient the window will be. No style of window is more energy efficient than the other, it’s the manufacturing process and how well the window (overall) from the frame to the glass, performs, this is what’s important for energy efficiency and window energy rating guides.

Are C Rated windows any good?

They can be. Whilst they offer fewer benefits than an A rated or B rated window, C rated windows can often be a compromise between budget and energy efficiency. So it’s not worth ruling them out, if you have a limited budget for your double glazing spend, consider C rated windows. However, if budget isn’t a concern, go for a higher window rating where possible.