System boilers have a tank that stores hot water for your taps and shower etc. The water in your central heating is heated as needed and the heated water stored in the insulated tank remains hot but will gradually loose its heat. These are great for larger properties where you might need to draw hot water from the taps in different rooms at the same time.

Heat-only boilers are similar to system boilers, but they have separate tanks in the loft for storing cold water to increase the water pressure to your taps and shower. They’re great where the water pressure coming into the house is low, but they need the loft space for tanks so they aren’t suitable for flats or some smaller houses.

A combi boiler heats both the water for your central heating and the hot water you draw from taps on demand. They take up less space than other gas boilers because they don’t need any water storage tanks.