Combi vs System vs Conventional Boiler

A combi boiler heats water directly from the mains when you turn on a tap — no separate hot water cylinder or cold water storage tank needed.

Pros: Compact and space-saving, hot water on demand with no waiting, energy efficient since you only heat water when you need it, cheaper to install than other types, and the most popular boiler type in the UK.

Cons: Can struggle with multiple hot water outlets running simultaneously (e.g., two showers at once), not ideal for very large homes with high hot water demand, and relies on good mains water pressure.

Best for: Small to medium homes with 1–3 bedrooms and one bathroom. This covers most Birmingham terraces, semis, and flats.

A system boiler works with a hot water cylinder (usually in an airing cupboard) but doesn't need a cold water tank in the loft. Most components are built into the boiler itself.

Pros: Can supply hot water to multiple taps and showers simultaneously, compatible with solar thermal panels, provides strong water pressure, and easier to install than conventional boilers.

Cons: Requires space for a hot water cylinder, hot water supply is limited by the cylinder size and can run out, and slightly more expensive than a combi to install.

Best for: Medium to large homes with 3 or more bedrooms and two or more bathrooms.

A conventional (regular) boiler works with both a hot water cylinder AND a cold water storage tank, usually located in the loft. Water is heated and stored in the cylinder until needed.

Pros: Suitable for homes with older heating systems, can supply large volumes of hot water, compatible with solar thermal, and works well in areas with low mains water pressure.

Cons: Requires the most space due to the cylinder and loft tank, most complex and expensive to install, and generally less energy efficient than combi or system boilers.

Best for: Large homes with existing conventional systems, especially where replacing the pipework would be costly or disruptive.

For most Birmingham homes, a combi boiler is the best choice — it's the most efficient, most compact, and most cost-effective option.

For larger homes with multiple bathrooms, a system boiler provides the hot water capacity you need without the complexity of a conventional system.

The best way to decide is to get a free, no-obligation assessment from Empower Gas. We'll assess your property size, hot water demand, existing pipework, and budget to recommend the right boiler type for your home.