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Last Updated on January 24, 2021

Types of Boiler Systems – What Type Do I Have? Well Explained

Zac Houghton

Zac Houghton

Heating expert and founder of Loftera.

Your boiler is an essential appliance for your household; it regulates all the heating and hot water, so without it, the quality of our lives would be significantly lessened. However, despite the universal need for these devices, they come in various models and makes which can affect how they run and their efficiency. Below, we will explore the different types of boiler in the UK and assess the pros and cons of each. 

types of boiler

Table of Contents

What Are the Three Types of Boiler? 

The first thing to note is that there are three main types of boiler. These are the combi, system and heat only appliances. The difference comes in the degree of control each has over the heating and hot water in your home. Let’s have a closer look at them now.

Boiler Types Explained 


A combi, or combination boiler to give it its full title, is a system that utilises a built-in heat exchanger that is connected to your cold water mains. This allows the combi to instantly heat the cold water as required, as opposed to older boilers which have a tank of stored hot water. Because of this, there is no need for any extra cylinders, instead, it all goes through a single unit. There are both advantages and disadvantages to this modern device.

In the pros section, a combi boiler will take up much less space in the house then a non-combi boiler, as there is no need for any further tanks than the unit itself. Another benefit of this is that the water is heated the second you need it, so you won’t have to wait for an external tank to fill and heat up. Most manufacturers will offer guarantees of good working condition for all of the heater’s functions. 

However, there are a few things that may make you think twice about a combi boiler. To start, if multiple outlets are using the combi at the same time, then the flow rates will be significantly decreased. So, if you fancy a shower while someone else is using the hot water, it might be a bit more tepid than you would like. Furthermore, if your house already has less than stellar flow rates and water pressure, then a combi system might not function at its optimal capacity. 

Heat Only Boilers 

This type is the classic boiler that many households across the country will have grown up with and continue to have today. Sometimes called regular boilers, they use cylinders to pump hot water straight to the radiators in your home. There are two variants of these devices; open-vented heating systems, which uses a Feed and Expansion, or a sealed system, which uses an expansion vessel. You may have a back boiler, which is a heat-only device that is installed within a chimney and a fireplace.

Just like the combi systems, there are benefits and negatives to devices such as these. For example, if your property is on the older end of the spectrum, then it’s radiator systems might be similarly dated. Heat only boilers are perfect for these cases, as modern ones, such as a combi, may be too high in terms of water pressure and can cause a boiler leak. They are also fairly cost effective, as they are cheap to buy and maintain. The downside is that they may not be as efficient as more modern boilers and essential parts of the system, such as pumps and tanks, will most likely not be covered by the manufacturer’s warranty. 

System Boilers 

System boilers are similar to heat only boilers in that they both use hot water cylinders. However, there is a big difference, as these are never open vented and all the external components of a heat only appliance, such as tanks, pumps and valves, can be found within the boiler itself. Essentially, this is an updated version of the boiler we looked at in the previous section and might be a more desirable prospect if you’re looking to install a new boiler.

As always, there are pros and cons to these kinds of devices. Unlike combi boilers, system boilers can provide high quality flow rates to multiple outlets in the house at the same time, which can be a great benefit for homes demanding a large volume of hot water. Since most of the mechanisms are connected to the boiler itself, these are often covered by the warranty, which can be helpful if there is a breakdown. 

However, the quality flow rate of these boilers is reliant on your mains delivering a decent water pressure. If it doesn’t, then flow rates may be an issue. You also have to take the size of these boilers into account, as they are quite a bit larger than combi appliances, so this is something to consider before making a final decision.


What Type of Boiler Do I Need?

There are a few things to look out for when buying a new boiler. The first, and arguably most important, is to consider the current appliance it is replacing. In most cases, it might be cheaper to keep the current system, so if you need minor repairs, that’s probably a better bet than going for an entirely new model. However, if you are to increase your efficiency, or believe a different type would suit the needs of your house better than this might be the best option. This is usually the case for older properties using outdated models.

Another important factor is the size of the boiler. If your property is on the smaller side of the scale, then you may find available space to be at a premium. In that scenario, a heat only boiler might not be applicable, as you might not be able to fit the tank in. Combi boilers are the obvious choice here, as all their necessary components are integrated inside. This may be an issue if you have a high hot water demand though, combis struggle when multiple outlets are in use, so that is another thing to think about. 

What is the Best Type of Boiler?

This is a difficult question to answer, as it is entirely dependent on your current housing and heating system. The size and water demand for your property are the most important things to consider here. For example, a four-bedroom, detached house will have very different needs to a two-bedroom terrace property. The former will probably have multiple bathrooms and therefore, a high hot water usage. In this case, you would want a heat only or system boiler, so that all the outlets and radiators on the house run in perfect working order.

The two-bedroom terraced house is a much smaller property so not only will the water demand be lower, but you will also have less space to fit in all the necessary equipment. Here, the best thing would be a combi boiler, as it can be installed in a fairly limited area and won’t be tasked with supplying numerous outlets. Terraced and semi-detached properties tend to retain heat better than detached properties, as there are more internal walls to stop heat escaping and insulate any adjacent houses.

Find the Perfect Domestic Boiler Today 

Neglecting your boiler is a terrible mistake to make as if you’re not affording the proper level of care, your entire heating and hot water system could be at risk. That is why it is never a bad time to think about buying and installing a new boiler. As you can see from the information above, there are numerous considerations to make when choosing one. Be sure to research what your property needs and act accordingly. While a cheaper option may save you money in the short term, spending more on a top-quality boiler could be much more cost effective in the long run.

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