Combination (combi) boilers are extremely economical, making them the best-selling gas boiler in the country. Over 50% of boiler sales in the UK are combi boilers.
System boilers heat up water in advance in a hot water cylinder. This water is then distributed around your home whenever you put the heating on or use hot water.
Open vent boilers are also known as conventional, heat only or regular boilers. They have both a hot water cylinder and a cold water tank.
Back boilers attach to the back of a fireplace or stove and use excess heat for hot water and heating. They’re not very common but were very popular in the 1960s, 70s and 80s.
Biomass boilers run on wood pellets, chips or logs. They’re an environmentally-friendly alternative to gas or oil boilers or electric heating.