Gas condensing combi boilers are are by far the most popular choice of boiler in the UK. They are usually recommended because for the average household, they are the most efficient way to provide hot water and heating. Comprising or only one single unit, they are very space efficient and with new technology it is now possible to save even more space with an ultra compact model. Combi boilers are also very simple to install, operate and maintain.
As a rule, a 20-35kW combi boiler will generally be sufficient for an average 3-4 bedroom house, whilst those with ensuite bathrooms may find that a 30-35kW boiler is more suitable. Much bigger houses will typically need a larger 35-42kW boiler, although it may be worth considering a system boiler as an alternative.