Combi, system and regular boilers
Combi, system and regular boilers are all terms for the same thing. If you are replacing a boiler the chances are that the old one is one of these, although it will be less energy efficient than today’s models. They are a version of a condensing boiler, which means they have good energy efficiency, and low CO2 emissions. Heat lost during the day from the storage cylinder, could make them less energy efficient than a combi boiler because it doesn’t store hot water.
But heat loss can be minimised by good insulation of storage tanks and pipes. A disadvantage if space is tight in your abode, is the need for a hot water storage cylinder in the airing cupboard, and cold-water header tank together with an expansion tank in the loft.
With a regular system hot water is stored usually in a cylinder in the airing cupboard. It is always on tap and you don’t have the problems an instantaneous combi system can give, such as not being able to run more than one hot tap at a time. You also have the advantage that it will provide some warmth in the airing cupboard to help, quite literally, air the laundry in there. The system will also operate on any type of water pressure – so the problems combi boilers can have with low water pressure do not apply.