Boiler types explained, in plain English

There are three main types of boiler in UK homes. Each has trade-offs around hot water delivery, space requirements, and installation complexity.

Quick comparison

Feature	Combi	System	Regular
Hot water tank needed	No	Yes	Yes
Cold water tank in loft	No	No	Yes
Multiple bathrooms	Limited	Good	Good
Space required	Minimal	Moderate	Most
Installation complexity	Lower	Medium	Higher
Typical cost	Lower	Medium	Higher

Heats water directly from the mains when you turn on a tap. No tank needed, so ideal for smaller homes with limited space.

Best for: flats, small to medium houses, 1–2 bathrooms, and households that don't need hot water from multiple taps at once.

Works with a hot water cylinder but doesn't need a cold water tank in the loft. Delivers stronger flow to multiple outlets at once.

Best for: larger homes with two or more bathrooms, and households that often use hot water from several taps at the same time.

Traditional setup with both a hot water cylinder and a cold water tank in the loft. Often the simplest replacement if you already have this system.

Best for: homes with an existing regular boiler system, older properties with complex pipework, and very large hot water demands.

Room thermostat: Essential. Controls when the heating comes on based on the temperature in your home. A programmable thermostat lets you set different temperatures for different times of day.
Thermostatic radiator valves (TRVs): Worth having on most radiators. They let you control the temperature room by room, and they're simple and relatively inexpensive to add during installation.

Smart thermostats: Nice to have, not essential. They offer remote control and learning features, but a good programmable thermostat does the core job. Don't overpay for features you won't use.
Weather compensation: Adjusts boiler output based on the outside temperature. It can improve efficiency, but it adds cost and complexity. Worth considering, but not mandatory.

Brand wars — most major manufacturers make reliable boilers.
Minor efficiency differences — real-world savings are often smaller than claimed.
Premium features you'll never use — focus on what matters for your household.
Extended warranties beyond five years — often poor value.

Once you understand the type of boiler you need, look at realistic costs and learn how to choose an installer who will do the job properly.