A system boiler (also known as a closed or sealed system boiler) works on the principle of stored hot water. This means that you will need an airing cupboard or other space for the hot water storage tank. Although a tank is needed in the airing cupboard, a system boiler still needs less space than a traditional open vent or heating only boiler, which utilises a second tank in the loft. Also, many of the individual components of the heating and hot water system are built in, which means that installation is quicker, neater, easier and more efficient. With a system boiler you can run hot water from a range of outlets simultaneously, without someone else’s shower running cold on them. You will also get good water pressure.

A system boiler is a great choice for a larger home or family with hot water needs that can’t be met by a combi boiler, but who want to keep loft space free. You will need a tank in the airing cupboard though.

However, you’ll have to wait for water to be heated when you want it, and it could run out if it’s used too quickly.

Many people with older systems such as open vent boilers choose an unvented sealed system for their central heating and hot water. Although it is more expensive than simply replacing your boiler with the old system, you will be able to free up more space in your home.