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Boiler Ratings Explained

(with update for 2021 Electric Boilers)

What to look for when judging the energy efficiency.

Combi boilers A ratedIn order to make it easy to identify Energy Efficient Boiler Ratings, a system was introduced whereby an appliance would get an alphabetical & colour coded rating (similar to those you see on washing machines & fridges).

The grades ran from Green with “A” as good and to Red with “G” as not so good.

You will find it referred to as the SEDBUK rating and that stands for Seasonal Efficiency of Domestic Boilers in the UK – and bases its rating on “typical domestic conditions” of use in the average UK household.

However, from September 2015 this is being replaced with a new labeling / rating from the EU called The Energy Related Products Directive (ErP).

This is in fact good news because the latest energy labels guide consumers to more energy efficient appliances that in turn reduce running costs, not forgetting lowering the Carbon Footprint.

The Energy Related Products Directive or ErP

The Boiler manufacturer has the responsibility to make sure their appliances are compliant, but the installers will have responsibility for labelling the heating system that gets installed in your home as a whole.

It falls into 2 sections known as:

  1. Ecodesign –  manufacturers of boiler & heap pump appliances have to make products that meet specific energy efficiency levels, this would mean that at some point non-condensing boilers will be “no-more”

Some Products that fall within Ecodesign

  • Heating boilers, & water heaters (all variations)
  • Heat pumps, Solar Thermal, Hot Water Cylinders
  1. Energy Labeling. – The new label is what consumers will be interested in because this is the way to easily see what you are getting in terms of energy efficiency. From 09/2015 products will have the new label with ratings from “A++” to “G” – A is good – G is not so good

In summary, what is going to happen is that if you are buying a single appliance you can see at outset how good it performs from the ErP label from the manufacturer. However, when you fit the product as part of a “system” which includes other elements (such as a full central heating installation) the installer will have to add a “package label”

How to tell the efficiency of Electric Boilers – update for 2021

No matter what fuel they use, efficiency is usually shown by a percentage and also by the ErP rating.

But when you look at ratings of gas fired Vs Electric boilers, you may see that electric powered units can be as much as 99.5% energy efficient, but still have an ErP rating of “D”.

A 99.5% efficient electric boiler will waste only 0.5p, compared to a 93% efficient gas powered unit. Basically, you could say that 7p out of every £1.00 spent on heating is wasted with a gas boiler.

The ErP rating can be slightly misleading as it’s due to the way your home electricity supply is generated.

Nearly all gas appliances will get an A-rating, whilst most electric get a D-rating.

In short, electricity generation is considered to be a great deal more carbon emission intensive than natural gas and this is reflected in a “fuel factor” that is used to calculate the ErP.

So, you could say that even though your electric powered appliance van heat your water with virtually no heat loss, it gets a low ErP because the power station that generates the electricity has a high carbon footprint.

But remember, if you store your hot water in a tank that is not well insulated, the efficiency of your boiler is not going to be the biggest problem.

If you have more questions, then check out our FAQ’s article.


ERP label – Source Potterton Products (part of BAXI)

All labels will be from A++ to G & colour coded Green to Red.

  • This image Courtesy of Potterton (Part of BAXI)


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