Guide to Boiler Efficiency

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Written By: Experts | Last Updated: January 2022

There are various factors to consider when buying a new boiler with boiler efficiency in mind. With numerous products available on the market and different types of boilers to choose from, you might not know what you need to look for. One thing you need to take into consideration is the size and design of your home. Budget will be a deciding factor for many people, and physical limitations such as where to put the boiler are something else to be considered.

Something else that you should always bear in mind when looking for a boiler is how efficient it is. Indeed, boiler efficiency is one of the most important factors of all, for 3 main reasons:

  • Cost Savings: An efficient boiler will use less power to heat your home and provide hot water. Over a year, this can mean savings of hundreds of pounds, maybe more. Potential cost savings should also be weighed up against the cost of buying a boiler and having it installed. Although a particular model might cost more, it may well end up saving you money in the long term.
  •  Comfort: If you’re on a limited budget then there might be times when you’re reluctant to turn the heating on despite it being a little cold. Boiler efficiency means your monthly energy costs will be lower, making it more affordable to keep your home at comfortable temperatures.
  • Sustainability: Every year, the need to reduce our carbon footprint is becoming more apparent. We can all do our part by reducing how much energy we use in our homes, and an efficient boiler will help us achieve this. Not only will you be reducing your costs but you will also be helping to maintain the environment for our future generations.

As technology advances, boilers have become more increasingly efficient and one development that increased the efficiency of boilers considerably is the condensing boiler. Condensing boilers have been mandatory for all new gas boiler installations since 2005 in the UK.

What is a Condensing Boiler?

Before condensing boilers were introduced, much of the heat generated by a boiler was lost through the exhaust in the form of hot gases. Heat that just passes out of the system is lost energy that could otherwise have been used to do what a boiler is supposed to do – which is to heat water.

With a condensing boiler, this otherwise wasted heat is used to heat cool water as it makes its way back to the boiler from your radiators. Condensing boilers also have a larger heat exchanger than non-condensing boilers, helping to ensure that as much of the heat is transferred to the water as possible.

The cool water returning to the boiler cools the hot gases to the point where water condenses and this condensed water passes out through a drain. This system means that more of the heat that’s generated is used rather than just passing out of the flue, so less energy is needed to heat the water in your boiler.

A modern condensing boiler will operate at around 90-94% efficiency, while a non-condensing boiler will operate at around 75%-78% boiler efficiency. These numbers relate to how much of the heat created is used to actually heat water rather than just passing out of the system. With a condensing boiler, around 6%-10% of the energy you use is wasted, compared with around 22%-25% for a non-condensing boiler.

To put this in financial terms, between £6 and £10 is wasted for every £100 you spend on energy with a condensing boiler. With a non-condensing boiler, that number is closer to £22 to £25 for every £100 you spend. These numbers help make it easy to see how much money a condensing boiler can save you.

Boiler Efficiency Ratings

In the past, the boiler efficiency was rated according to the SEDBUK (Seasonal Efficiency of Domestic Boilers) classification. SEDBUK has since been replaced by ErP (Energy related Products Directive), but you will find that a lot of boilers are still rated using the SEDBUK classification.

SEDBUK ratings are graded from A to G, with ‘A’ being the best grade at 90% efficiency or better. Grade ‘B’ means between 86% and 90% efficiency, and grade ‘C’ means between 82% and 86%. ErP classifications start from A*** for the most efficient, followed by A**, then A*, A, B, C, and finally, D.

The ErP directive from SEDBUK means that an engineer installing a boiler for you is expected to calculate how efficient your installation is, taking into account all components of the system. This is beneficial to you because it means engineers need to make sure your system is as efficient as possible, thus helping to save your money.

Can I Increase My Boiler Efficiency?

Condensing boilers are a lot more energy efficient than older designs, but there is still more you can do to reduce how much energy you use. These include:

  • Programmable Thermostats

Many houses will be left empty during the day, particularly during the week when their occupants are at work. Many houses won’t need any heating during this time and programmable thermostats help ensure you only use energy when you need to. Set the timer for around 15-20 minutes before you get home from work and you can still have hot water and a warm house waiting for you.

  • Modulation

Modulation means that a boiler can reduce its output according to your needs. Instead of switching the heating power supply on or off as is the case in boilers without modulation, it can instead be turned down. Modulation helps to improve efficiency further, while it also helps to reduce wear and tear on components.

  • Smart Controls

Smart controls let you adjust your heating from your smartphone or other device. Not only that, but smart controls can also learn your habits and know when your heating can be turned down to save energy.

A new boiler is a relatively large investment and will have a considerable impact on much you pay on heating each month. This makes it worth your while to take your time and make sure you get an efficient boiler to reduce your bills, help make your home more comfortable, and help do your bit to help the environment.