What Is a Combi-Boiler and Is It Worth It?

A combi-boiler—short for combination boiler—is a type of gas (or sometimes oil) boiler that provides central heating and hot water directly from the mains supply. Unlike traditional systems, it doesn’t require a separate hot-water cylinder or cold-water tank.

In most homes, this means you get hot water whenever you open a tap or run a shower, while the boiler simultaneously supports heating through radiators (or underfloor heating). The key idea is “on demand,” rather than storing hot water in advance.