System boilers are like a middle ground between the smallest, combi boilers and the larger, regular types of high efficiency condensing boiler.
They are “heat only” boilers that, like a regular boiler, use a copper cylinder to heat and store your hot water. However being condensing boilers, they can be more than 90% efficient, cutting your energy bills and your environmental damage.
System boilers eliminate the need for a cold water feed tank in your loft by heating water straight from the mains, like a combi boiler. However, system boilers keep the hot water storage tank used by regular boilers and usually found in your airing cupboard. They are a sort of middle ground between the two boiler systems.
System boilers have all of their components built into the boiler, offering a compact and attractive installation. They also allow you to do away with the loft tank, freeing up more space in your home and leaving you with less external components to maintain.
But by keeping the hot water storage tank, while it will then take up more space than a combi boiler, the system boiler can provide hot water from more than one outlet, and at a higher pressure.