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There are three main types of boilers – regular, combi, and system. Choosing from these three options is not that simple. You have to consider several factors. The number of bathrooms, size of your house, water pressure in your area and the number of showers are a few to name.

When you are thinking of buying a new boiler, the one you choose must identify with your needs. For that, you must understand what purpose each type of boiler meets.

Types of Boilers

As you look for boilers for your property, you will come across these options:

1.) Conventional Boiler

You will hear boiler installers calling a conventional boiler a heat-only unit and regular boiler. It’s a traditional model mostly found on older properties. It is commonly located in the loft as it requires extra space to store hot water cylinder and a cold-water tank.

A conventional boiler generates heat for the central heating of the property directly. It uses the hot water cylinder for producing and storing hot water. When you open the hot water tap, the boiler draws hot water from the storage.

The boiler system includes a hot water cylinder, heating controls, cold water tank, and an expansion cistern.

Advantages of a Conventional Boiler

  • The pressure of the mains does not affect the performance of the boiler.
  • You can use multiple hot water outlets at the same time without compromise on hot water supply.
  • They are easy to maintain.
  • If the boiler breaks down, you can still get hot water supply by installing an immersion heater to the hot water cylinder.

Drawbacks of a Conventional Boiler

  • The water pressure flow in showers can be low if multiple outlets are in use.
  • Extra storage space is required for hot and cold tanks.
  • They are not efficient. Hot water stored in the tank is a waste when it’s not in use.
  • Users often complain about running out of hot water. Reheating the water takes time.
  • Hot water is not available on demand.

2.) Combi Boiler

A combi boiler or combination boiler has the ability to combine dual functionality of heating the house and generating hot water from a single boiler unit. The boiler heats water from a heat exchanger and you get hot water supply on demand.

A combi boiler is different from a traditional boiler. It does not have a water cylinder or a tank. Therefore, this eliminates the need for having a storage space. This wall-hung unit does all the work.

Advantages of a Combi Boiler

  • All components are installed within the boiler. There are no external tanks with the unit.
  • The boiler is compact and neat. There is no need for extra storage space.
  • Hot water is available on demand.
  • The boiler is highly energy-efficient.

Drawbacks of a Combi Boiler

  • Multiple users cannot use hot water at the same time.
  • If the boiler breaks down, you will be without hot water and heating.
  • For the combi boiler to work well, the water pressure of the mains must be good.

3.) System Boiler

Also known as a closed vent boiler, a system boiler is a heat-only boiler that does not have a lot of external components. All the components are built into the body of the boiler. It still needs an external hot water cylinder. However, the feed and expansion tank is replaced by an expansion vessel.

The water supply comes from the mains directly hence why it does not require a separate water tank. The cold water enters the boiler from the mains supply directly. The heat exchanger heats the water by transferring energy from the gas jets to the water. Once the water is heated, it is pumped to the hot water cylinder for storage purposes.

Advantages of a System Boiler

  • System boilers are good for large homes.
  • It’s a great choice if you live in an area where water pressure in the mains is low.
  • Since most of the components are built-in, it is easy to install.
  • It does not have a feed and expansion tank.

Drawbacks of a System Boiler

  • You will need storage space for a hot water cylinder.
  • It’s not as efficient as a combi boiler since hot water tank can lose heat.
  • You will have to wait for the supply of hot water.

Conventional Boiler Vs Combi Boiler Vs System Boiler

This table comparison shows the differences between conventional, combi, and system boiler:

Conventional Combi System
Property size Large homes Small homes Large to medium-sized homes
Storage space Extra storage space required No storage space required Extra storage space required
Efficiency low high Moderate
Hot water supply Hot water is stored in the cylinder Hot water is available on demand Hot water is stored in the cylinder
Immersion pump Can be used for meeting hot water needs in case of a boiler breakdown Cannot be used in case of a boiler breakdown Can be used for meeting hot water needs in case of a boiler breakdown
Water usage Hot water can be served to multiple outlets One person can use hot water at a time Hot water can be served to multiple outlets

Other Options in Boilers

Apart from the 3 main types of boilers discussed above, here are some other options you may come across:

Back Boiler: It is another type of conventional boiler that has a gas space heater hire at its back. It is also a heat-only system with built-in storage. It is suitable for properties with higher hot water demands. You can also operate it with an external hot water cylinder storage.

Oil Boiler: It works in a similar way as a gas boiler. The only difference is that the fuel used is stored on the site. It does not come off the gird. It is a reliable boiler but expensive. It is not an environmentally-friendly choice.

CHP Boiler: It is a Combined Heat and Power Boiler that provides hot water and generates electricity for the house. In other words, it is a micro-power plant.

Electric Boiler: It suitable to use in areas where a gas supply is not available. It is a 100 percent efficient unit. However, the cost of heating water with electricity is higher as compared to gas. Therefore, it’s not the first choice for many households.

Condensing Boiler – Is it a separate type of boiler?

When searching for types of boilers, the term condensing boiler will appear often. Keep in mind, a condensing boiler is not a separate type of boiler. It is rather a function of modern boilers which makes them more efficient.

Condensing boilers capture the heat given off the boiler’s flue and use it for heating the water. Hence, the boiler uses less gas for powering the heating system. All combi boilers are usually condensing boilers. The UK building regulations have made it compulsory for all new gas boilers to use condensing technology.

Condensing boilers are safer to use than conventional boilers. They capture air from outside the storage room and seal it for heat insulation. The boiler does not suck anything. This reduces the chances of getting in contact with toxins because the condensed liquid is disposed of through a pipe that has a connection with the drainage system.

Which Boiler Is Right for Me?

Whether you are buying a new boiler or a replacement boiler, knowing a few key things will help you decide which type of boiler is the right fit for your property.

Here is all the information you need to decide which boiler will suit the size of your property and household needs:

Family Members in the House: The number of people in the house will help you decide what size of boiler you need. If you end up choosing a small boiler, it will fail to meet the heating and hot water demands of your house. Similarly, if you choose a larger size, it will produce more energy and increase your heating bill.

If you have a large house and a large family, choose a conventional or system boiler. On the other hand, if you have a smaller house with 2 family members, your heating and hot water needs are likely to be limited. Therefore, you are better off with a combi boiler.

Number of Bathrooms: If you have more than two bathrooms and you use them at the same time, you will need the hot water supply at the same time. In that case, you should choose a conventional boiler provided that you have a large house and extra storage space. Choose a system boiler if you don’t have a loft or an additional storage space.

If you have a single bathroom and one person uses hot water at a time, a combi boiler will suit your needs.

Availability of Free Space: Some boilers can handle the hot water and heating demands better than others can. However, your choice is limited on the basis of free space available. Do you have a loft or an airing cupboard in your home?

If your demands for hot water and heating are higher and you have a loft or extra storage space available, don’t hesitate to get a conventional boiler. The tanks and cylinder will fit in this storage unit.

If your heat and hot water needs are higher but you don’t have a loft to store the tank, a system boiler is a better option for you. It works similar to a conventional boiler but it does not have separate components. It only uses one external cylinder for the purpose of storing hot water. You won’t need a loft for storing the cylinder though. It’s a great option for homes with limited space.

If your demands for heat and hot water are low and you live in a flat or a small house, choose a combi boiler. It supplies hot water on demand. The unit does not have a tank and cylinder therefore, you won’t need extra storage space.

Number of Radiators: The number of radiators helps determine the boiler output in kW. If you live in a small house that has 10 or fewer radiators, a boiler between 24 and 27 kW will be enough. If you have a 3-bedroom house, choose a boiler with an output between 28 and 34 kW.  On the other hand, boilers with output between 35 and 42 kW are suitable for large homes.

Energy Efficiency Needs: Efficiency is important for every household. Some want to reduce their heating bills whereas others want to reduce carbon footprint. The heating system accounts for 55 percent of annual energy bills. Therefore, by choosing an efficient boiler, you can bring down your energy bill.

Modern boilers are a lot efficient than traditional boilers. They are all condensing boilers. They are condensed to ensure every bit of the fuel is consumed to convert heat for the home.

Conventional boilers are usually a G-rated boiler which makes them less energy-efficient. Combi boilers are A-rated boilers. They are highly energy-efficient. Some also have ECO mode for improving the control of hot water and heating by maintaining the boiler temperature.

Warranty: Comparing the length of warranty of the boiler will give you a good idea about the quality of the product. Boilers that have an extended warranty are reliable in performance. On average, if you maintain the boiler well, it can last for up to 15 years.

Summing Up

There are three main types of boilers. A conventional boiler is the oldest type of boiler suitable for large homes with higher heating and hot water needs. Combi boiler is a modern boiler that is fit for small homes. A system boiler is similar to a conventional boiler with one exception – it does not need a feed tank. It’s also ideal for medium to large homes.

The type of boiler you choose depends on the heating and hot water needs of your home, number of radiators, energy-efficiency requirement, number of bathrooms, and availability of space. Therefore, evaluate your needs before you head out to buy a boiler. This will speed up the purchase.

Different Types of Boiler What Are the Options Available