What is a Combi Boiler?

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Most take our boilers for granted. Understanding how integral they are to the home is usually only considered when you are looking to have them repaired, services or even replaced. The boiler industry is full of various boiler types now, this is mainly due to the greener home people want to run, or the advances in technology. If you live in a standard residential property, most engineers will recommend a combi boiler, however what is a combi boiler? In this article we will explore just that. 

What Is A Combi Boiler? 

Let’s start with the overall question, of what is a combi boiler. A combi boiler in short is a combination boiler as it is made from a single unit which serves two functions. Heating and Hot Water. A combi boiler is a unique piece of kit, and really does help a home to be more efficient. This is because you are able to draw on hot water when required, with no need to wait for the tank to fill up. This is another reason why they are popular due to not needing a separate tank.

How Does A Combi Boiler Work?

A Combi Boiler by far has the simplest of workings. The boiler will take water from the mains, and when the hot tap is turned on ignite a powerful system called a heat exchanger. This heat exchanger transfers high amounts of energy to nearly instantly heat the water. 

To also make this process faster, you will find most modern boilers have a built in pre-heat system. This pre-heat system is a small amount of water that is always kept at an optimum temperature. In order to do this your boiler may turn on once per hour. This allows the water to be heated, and create that instant flow of hot water. To make your boiler more efficient it is possible to turn this off. However, this would affect your flow of hot water, so it is not recommended.

What Is Condensing Technology?

Condensing technology is now a UK requirement for all gas combi boilers. The rules were put in place in order to help homeowners benefit from an increased efficiency. Prior to this, 50% of heat energy was being lost in boilers due to combustion gases being lost into the flue. A condensing boiler contains that heat within the gases, and is used to preheat the cold water. This therefore makes the efficiency rise, as your boiler is not required to use as much heat to heat the water.

Why Should I Choose a Gas Combi Boiler?

A gas condensing combi boiler is by far the most popular, and most recommended within the UK at the moment. This is mainly due to the benefits, and ease of use of the average household. This boiler type can provide hot water on demand without the need for an external tank, and also heating. The space efficiency is also a benefit, with the average home consisting of very little storage space. Combi boilers are also very easy to install, operate and most importantly maintain.

Advantages of a Combi Boiler

As we have highlighted above a combi boiler does have any benefits, and can really benefit your home once it has been installed. Some of the advantages we explain to our clients are as follows:

  • High Energy Efficiency

As of 2018 all new combi boilers were legally required to operate at least 92% efficiency, which ultimately changed the boiler industry. This means less wastage from the outset, and a better technology set to make your boiler operate fully. A higher efficiency has a direct link to lower heating bills.

  • Lower Energy Bills 

As mentioned above, when combi boilers were legally made to be 92% efficient this had a direct effect on the cost of using energy within your home. With a new boiler being more efficient, this means you will have less wastage when it is being used.

  • Compact Size

Unlike their traditional or system counterparts, a combi boiler is one compact unit. Therefore ridding the need for a bulky water tank, which ultimately takes up more room within your home. By not having that separate system, they are able to fit into smaller places like a kitchen or upstairs cupboard which will save you space.

  • Easy to Install 

Due to the set up of a combi boiler there is no need to connect it to a hot water cylinder or feed tank in the attic. This means it can be fitted anywhere within the home, and make the job a lot easier. Also as it is the most common boiler to be installed, many homes already have existing infrastructure for it all.

  • Hot Water On Demand 

One major benefit to a combi boiler is the instant hot water. This will eliminate any waiting around for water, or for the tank to refill when the water has gone.

To Conclude


When it comes to choosing a boiler for your home the options are somewhat endless. This article has been focused around what is a combi boiler, and should have provided you with an insight to what their inner workings are and also their benefits. At Greener Homes we understand that the decision is not always that easy. We are always on hand to offer our expert advice. For more information on our services head over to our Quote Tool.