Combi, system or regular boiler: which suits your home?

When you replace a boiler, it is a good moment to ask whether you have the right type for your home. There are three main kinds.

Combi boilers

A combi heats water instantly from the mains, with no hot water cylinder or tanks in the loft.

• Saves space, as there is no cylinder cupboard.

• Hot water on demand, so you never run out.

• Best for flats and smaller houses with one bathroom and good mains water pressure.

• Can struggle to supply two showers at once.

System boilers

A system boiler heats a separate hot water cylinder, usually an unvented cylinder fed directly from the mains.

• Supplies several bathrooms at the same time with strong pressure.

• Suits larger family homes with two or more bathrooms.

• Needs space for a cylinder, but no loft tanks.

• Works well alongside solar thermal or a future heat pump.

Regular (conventional) boilers

A regular boiler works with a hot water cylinder and cold water tanks in the loft.

• Common in older houses where the existing pipework was designed for it.

• Can work well with lower mains pressure.

• Takes up the most space.

How to choose

• Count your bathrooms and think about how many showers run at once.

• Check your mains water pressure and flow rate.

• Consider the space you have, and whether you want to free up the airing cupboard or loft.

• Think ahead: if you might switch to a heat pump, keeping a cylinder can make that easier.

Get expert advice

The Essential Connection installs combi, system and regular boilers across Walton-on-Thames, Weybridge, Cobham, Esher, Kingston and South West London. Book a survey and we will recommend the right option for your home.