Condensing Boilers

Heating now accounts for around 60% of the average household’s annual energy bills, so it’s worth making your heating system as efficient as possible.

Replacing your old gas or oil boiler with an efficient condensing boiler can save you around £225 a year on your bills, and if you are using electric heating, switching to an oil or gas condensing boiler can save you around £500 a year.

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The Basics

Condensing boilers are a newer, more efficient type of boiler. They are very similar to standard boilers, but have an additional heat exchanger. Boilers produce hot gases that escape through your boiler’s flue. The second heat exchanger reclaims heat from these hot gases, meaning that you have to use less fuel to heat your water, saving you carbon emissions and money.

Condensing boilers are as much as 12% more efficient than standard boilers, and from 2005, all boilers fitted in UK homes must be condensing boilers apart from in exceptional circumstances. From 2010, this was narrowed to include only boilers that are ‘A’ rated or 88% efficient on the SEDBUK scale. Regulations also state that you will have to have a time and temperature control fitted as part of the installation, to maximise the efficiency of your system.

There are two main types of Condensing Boiler:

  1. Combi (Combination) -  These don’t need a water tank as they heat the water ‘on demand’ when it is needed, such as when you turn the tap on. This means that you don’t need to wait for your water to heat and you can save the space of a hot water tank. They are more efficient than system boilers, but have lower capacities, so are generally used for smaller homes.
  2. System or Open Vent – These have a tank to store hot water and are better at providing water for larger homes with multiple bathrooms or showers, particularly if you might need to run them at the same time. You will get need an airing cupboard or another place where the hot water tank will be housed.

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FAQs

What is a condensing boiler?
A condensing boiler works on the principle of recovering as much as possible of the waste heat which normally leaves through the flue of a conventional (non-condensing) boiler as water vapour. The best high efficiency condensing boilers convert more than 95% of their fuel into heat, compared to 78% for conventional types. Condensing boilers get their name because as they recapture the heat from the water vapour leaving through the flue, this water vapour condenses back to a liquid, or condensate as it is known.
How often should I get my condensing boiler serviced?
It's important to have any gas or oil fired appliance like a condensing boiler serviced once a year. The flue will need checking to make sure it is clear, and a qualified installer should check that your boiler is running safely and efficiently for you. It's best to check with your manufacturer about service schedules, as some boilers may need servicing more than others.
How easy is it to install a condensing boiler?
Boilers vary in size and shape but most are designed for simplicity of installation. With space being such a premium many boilers are small enough to be fitted by one person into a kitchen cupboard, easily and with minimum disruption.
What does the Sedbuk efficiency rating mean?
Sedbuk stands for 'seasonal efficiency of a domestic boiler in the UK' and is now given as a percentage score. This score is an estimate of efficiency when the boiler is installed under typical conditions in Britain, taking into account climate, housing conditions, occupancy patterns, and controls.
If I buy a new boiler, does it have to be a condensing boiler?
Yes. Government legislation now requires all new boilers to be the condensing type unless it would be impossible to fit one, which would probably be the case if there was no way to provide suitable drainage.
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