Combi, system or regular: which boiler is right for your home?

The short version

Most UK homes are best suited to one of three boiler types: combi, system, or regular (sometimes called conventional or heat-only). The right one for you mostly comes down to how many bathrooms you have, how much hot water your household uses at once, and how much space you've got.

Combi boilers

A combi (combination) boiler heats water directly from the mains on demand, so there's no hot water cylinder or cold water tank to find space for. That makes it the simplest, most space-efficient option, and it's why combis are now the most common choice in flats and smaller homes.

The trade-off is flow rate: because everything is heated instantly, running two hot taps or a shower and a bath at the same time can mean the pressure drops. If you've only got one bathroom, or two that are rarely used simultaneously, this usually isn't an issue in practice.

System boilers

A system boiler heats water and stores it in a hot water cylinder, but most of the major components are built into the boiler itself rather than in the loft. That means better performance if you've got multiple bathrooms wanting hot water at once, without needing a separate cold water tank taking up loft space.

This tends to suit medium to larger homes with two or more bathrooms, where a combi's flow rate would start to feel limiting.

Regular (conventional) boilers

A regular boiler works with both a hot water cylinder and a cold water storage tank (usually in the loft). It's the traditional setup, and it's often the right choice when you're replacing an existing regular boiler like-for-like, since the pipework and tanks are already in place.

Regular boilers can supply strong pressure to multiple bathrooms at once, which is why they're still common in larger, older houses — though they do need more space than a combi or system boiler.

Not sure which you've got?

If you're replacing a boiler, we'll ask a few quick questions about your current setup — including whether you have a hot water cylinder — and recommend the right type for your home as part of your quote. You don't need to know the exact model beforehand.