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

Boiler marketing makes this sound complicated. It mostly isn't — the right type falls out of three questions: how many bathrooms run at once, how strong your incoming mains supply is, and whether you have space (and patience) for tanks and cylinders.

Combi: the default for most homes

A combi heats water the moment you open a tap — no cylinder, no loft tanks, no waiting for a tank to reheat, and the airing cupboard becomes storage. The catch: it heats water at the rate your mains can supply it, so two showers at once means two lukewarm showers. One bathroom and reasonable mains pressure? A combi is almost always the answer.

System: for busy bathrooms

A system boiler heats a cylinder — ideally an unvented one running at mains pressure — so several outlets can run hot together with proper force. No loft tanks needed. The trade-offs are the cylinder's space and the fact that stored water eventually runs out and reheats. Two or more bathrooms in regular use points here.

Regular (heat-only): the incumbent

The traditional setup — loft tanks feeding a cylinder — survives in many older homes, and where the pipework was designed around it, keeping like-for-like is sometimes the pragmatic choice, especially if the mains supply wouldn't feed a combi or unvented cylinder well. It's rarely what we'd design from scratch, but honest advice sometimes means leaving a working architecture alone.

The measurement that decides it

Mains flow and pressure. A combi or unvented cylinder is only as good as the supply feeding it, which is why we measure at the kitchen tap before recommending anything — a two-minute test that prevents a four-figure mistake.