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

Is a combination condensing boiler more efficient than a regular condensing boiler?
A combination (Combi) condensing boiler can be more efficient than a standard condensing boiler because it heats water as you need it. Combi boilers are most suitable for smaller homes, as they can only keep up with a certain level of demand. Non-combi boilers produce hot water and then store it in a cylinder for use as and when. This is still quite an efficient process - but if the hot water is not used immediately, then inevitably some heat will be wasted. It will generally depend on the size and amount of hot water you're likely to need. You installer will be able to advise you which type of boiler best suits your needs.
How can a condensing boiler save me money on my energy bills?
Condensing boilers are more efficient than standard boilers and therefore utilise less gas during operation. Modern conventional boilers can only offer a typical efficiency rate of 78%, whereas the rate for condensing boilers is around 88% - i.e. for every £1 spent spent on gas, 88p is converted to actual heat. This adds up to significant savings on annual gas bills, which will enable you to quickly recoup the initial outlay for the boiler and benefit from the extra savings. Complete our Home Energy Survey to find out just how long payback will take in your situation.
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.
How reliable are condensing boilers?
Condensing boilers are reliable if well maintained and serviced regularly. A Which? survey in 2011 found that 46% of owners who bought a boiler after April 2005 have experienced some kind of fault. Not all of these faults required a repair. In fact the most frequent problem, a blocked drainage pipe, experienced by 11% of owners, is actually a problem caused by poor installation.
Could a condensing boiler save money on my energy bill?
Which? estimates that the average efficiency of boilers in UK homes is about 70%. This means they waste up to 30% of the heat they generate in the form of hot flue gases. This suggests that installing a condensing boiler, which has an efficiency of around 88%, can reasonably achieve savings of between £50 and £200 per year depending on the size of your house - and the saving will increase as the cost of gas increases. Complete our free assessment to find out just how much you could save.
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