The high efficiency condensing combination boiler is an space-saving idea. Combi boiler are the majority of all the new domestic boilers installed in the UK.
They have been around for about 30 years and have gained massive populatity in the last 10 years or so
The major difference between a combi boiler and any other type of boiler is that a combi boiler eliminates the need to store hot water — so no hot water cylinder in the airing cupboard is required. It is both a high-efficiency water heater and central heating boiler, combined (hence the name) within one compact unit which usually sits in the kitchen or utility room, or in the airing cupboard generally with a vertical flue.
The space savings result from the fact there is no hot water storage cylinder, cold water storage cistern or other familiar components of a regular (conventional) heating system. The further benefits of this are a significant saving on hot water costs, and the fact that hot water is delivered through your taps or shower at mains pressure. So you can enjoy powerful showering* without the need for a pump. Another combi benefit is that it can generally save you money on installation time and costs — no tanks in the roof space means less pipe work and less things to go wrong.