The high efficiency combination boilers are becoming an increasingly popular choice in UK homes and now account for well over half of all the new domestic boilers installed in Britain every year.

The major difference between a combination boiler and any other type of boiler is that a combi eliminates the need to store hot water, so there is no hot water cylinder in the airing cupboard. It is both a high-efficiency water heater and central heating boiler, hence the name. The space saving is due to the fact that there is no hot water storage cylinder, cold water storage cistern or other familiar components of a regular (conventional) heating system.