When homeowners compare a combi boiler with a separate boiler plus hot water cylinder (often called “system” or “heat-only” setups), the decision usually comes down to how you use hot water, how much space you have, and your priorities for efficiency and installation cost.
Both options can deliver reliable heating and hot water, but they behave differently—especially when multiple taps are used at once.
What a combi boiler does (and doesn’t)
A combi boiler (combination boiler) heats water directly from the mains when you open a hot tap, so you typically don’t need a separate hot water cylinder. This “on-demand” approach often appeals to smaller homes or properties where cupboard space is limited.
Pros:
- Usually simpler installation because there’s no cylinder to fit.
- Hot water is available o ... Read more »





