System Boilers Explained

A system boiler is an excellent option for busy households. A system boiler works in a similar way to a regular (conventional) boiler but it draws the water directly from the mains supply. A system boiler heats your central heating system in addition to producing hot water for your storage cylinder. 

How does a system boiler work?

There are two main components for a system boiler setup. The boiler contains everything required to generate hot water and heat your home. There is also an external cylinder or tank which stores your hot water. This hot water tank may be replenished once or twice a day or topped upon demand. This ensures you will always have a supply of hot water for your home.

The water for the system is taken directly from the mains water supply. This means that you do not need a tank of water in your loft as you would with a regular boiler. All you need for a system boiler is your boiler unit and a storage tank which can usually be housed in an airing cupboard.

Advantages of a system boiler

Easier to install

Since there are fewer components involved and the boiler houses all the components needed to heat water for your home, the installation process is typically quicker and neater. By keeping all the components within the boiler, this results in a more compact unit which takes up less space in your home. The storage tank can be easily housed in an airing cupboard.

Great for busy households

Since the hot water is supplied from a storage tank, you can use it from multiple sources in the home without experiencing a loss of pressure. This makes it ideal for busy households where multiple taps might be used at once.

Excellent water pressure

With a regular boiler system, you will rely on gravity to provide the water pressure. Since system boilers are supplied by your mains water supply, you will experience higher water pressure than with a regular boiler.

Economical and fast

It is often more economical to run a system boiler. This type of boiler has a pump which makes it quick to respond to demand. By properly insulating your storage cylinder, you can increase efficiency and ensure limited heat loss.

No cold feed water tank is required

With a system boiler, you don’t need a feed and expansion tank or a cold water feed tank. This can save a lot of space and also means that you can install a system boiler even if you don’t have a loft. This makes it a suitable and efficient option for apartment buildings.

Works with solar thermal

Heating your home and hot water with solar energy is a great way to save money and reduce your carbon footprint. If this is a priority, then a system boiler is worth considering. The tank that stores your hot water can be adjusted to allow it to heat water using solar power.

Things you need to consider before installing a system boiler

You need to have space

A system boiler takes up less space in your home than a regular boiler but it takes more space than a combi boiler. This is because you will also need a space for the hot water tank. If you’re looking for a space-saving solution and you aren’t a high consumption household, a combi boiler might be more appropriate.

The tank has to be insulated

If you don’t properly insulate your tank, it will cost you more to generate hot water for your home. Heat loss from your hot water cylinder can make your system boiler very inefficient so you have to ensure it is sufficiently insulated. It’s quite cheap to insulate a hot water cylinder so this isn’t a disadvantage, just something to consider.

Hot water isn’t available on demand

With a combi boiler, you can enjoy hot water on demand. With a system boiler, the amount of hot water you can use will be decided by the size of your tank. Once the hot water runs out, you will have to wait for the system boiler to heat more water.

Which system boiler brand should I choose?

Many of the top boiler manufacturers create system boilers. These include Vaillant, Ideal and Worcester-Bosch. Below you can see a brief overview of some of the system boilers we believe offer good value for money and reliability.





Warranty duration

Up to 10 years

2-7 years

2-5 years

Potential efficiency




Output capacity




How much does a system boiler cost to install?

This will depend on the model of boiler you choose and how much work is required in your home. Replacing an existing system boiler will be less expensive than replacing a combi boiler with a system boiler. The price of your new system boiler could vary from between £500 to £3,500. You will also need to factor in the cost of installing the boiler. We would recommend getting a few different quotes to find the best deal.

How can I maintain my system boiler?

Like any other type of boiler, you should have your system boiler serviced every year. With a home and boiler care plan from YourRepair, you can enjoy peace of mind knowing that your boiler is covered in the event of a breakdown. You will also get a free annual boiler service worth £80. This can help to prolong the life of your boiler and ensure you always have hot water and heating.