Definition: A combi (combination) boiler heats your home and provides instant hot water from one unit, with no separate cylinder or tanks. It’s the most common boiler type in UK homes.

Pros and cons

Space-saving, efficient, and cheaper to install (£1,800-£3,000). Hot water flow drops if two showers run at once — larger households may prefer a system boiler with a cylinder.

When to choose one

Ideal for flats and homes with one bathroom. If you might switch to a heat pump later, note heat pumps need a cylinder — a system layout is more future-proof.

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