System Boilers: Cost, Efficiency & How They Work

System boilers explained. Is this the best boiler for your home? Find out.

A system boiler is also called a sealed system boiler. It takes water directly from the mains heats it, stores it in a hot water tank and delivers the hot water to your radiators. It is similar to a conventional boiler with the main difference being that it takes water directly from the mains supply.

The installation process of a system boiler is quick and efficient as most of the main components, like the pump and expansion vessel, are built into the boiler.

What’s In This Guide to System Boilers?

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System boilers are efficient, convenient, and eco-friendly whilst also being compact. They are the perfect option for houses that use a large volume of hot water but having limited space.


System Boilers Types

System boilers are usually categorised into two types: vented and sealed system boilers. While vented boilers use an external expansion vessel, sealed system boilers have it built in.

For both of these types, you will need to install a hot water tank. However, if an unvented cylinder is installed together with a sealed system boiler, cold-water storage won’t be required.

System Boiler: What Is It?

A system boiler is similar to a combi boiler, as it heats the water directly from the mains. This type of boiler is beneficial for houses and apartments that require a dry roof space. A system boiler pumps hot water directly to the radiators and the hot water tank through the heating system. It’s fast and efficient which helps to reduce heating costs.


A system boiler generates water for more than one outlet thanks to the hot water coming from the storage tank. This makes the system boiler reliant on  pressure in the cold water pipes. It provides higher water pressure than a combi boiler and can therefore be used in areas with low water pressure.

System Boilers : The Advantages

Compared to a conventional boiler, a system boiler is easy and quick to install, and you won’t have a lot of debris left after installation. The reason for this is that most of the heating and hot water system components are built in. It’s compact and only requires additional space for the hot water tank.

The large water storage tank allows you to use several taps at the same time without reducing water pressure. It makes system boilers perfect for busy households with several bathrooms.

Since water is coming from the hot water storage tank in the roof, you can rely on better water pressure, even when more than one tap is running at the same time.

With a system boiler, there is no need for a cold water feed tank because they utilise hermetic cylinders. It means that even if you don’t have a loft, you can still install a system boiler and save space.

If you prefer using renewed energy to power the appliances in your house, you should consider installing a system boiler. You can alter the water storage tank to heat water using solar energy.


System Boilers : The Disadvantages

The system boilers’ water cylinder should be well insulated when installed. Otherwise, they may lose heat to its surrounding area, wasting energy.

Even though system boilers are rather compact, they may take more space than combi boilers.

Since system boilers use the water storage tanks, the amount of water available for your use will directly depend on the size of your storage tank.

What Does a System Boiler Cost?

System boilers come in a wide variety of models with different prices. It will also depend on fuel type, heating capacity, efficiency, size, etc. However, system boilers are generally priced lower than combi boilers or combustion boilers.

If you are thinking about getting a gas boiler replacement, be sure to research all your options before making a decision.