Picking the wrong boiler type is the single most expensive boiler-buying mistake. Here's how to choose between the three main types based on your actual home, not on what the showroom prefers to sell.
Combi boiler
A combi (combination) boiler heats hot water on demand from the mains. No hot water cylinder, no cold water tank in the loft. Best for 1 to 2 bathroom homes with good mains pressure.
- Pros: compact, efficient, no tanks, instant hot water
- Cons: hot water flow drops if two taps are used at once
- Best for: flats, terraced houses, small to medium homes
- Typical install: £2,200 to £3,500
System boiler
A system boiler heats water and stores it in a hot water cylinder (usually an unvented one in the airing cupboard). Best for larger homes where multiple bathrooms might run hot water at the same time.
- Pros: strong simultaneous hot water flow, works with low mains pressure
- Cons: needs cylinder space, hot water runs out if cylinder empties
- Best for: 3+ bathroom homes, family households
- Typical install: £2,800 to £4,500
Regular (conventional) boiler
A regular boiler uses a hot water cylinder AND a cold water tank in the loft. Older system, less common in new installs, but the right choice when you're replacing like-for-like and the existing system works well.
- Pros: works with very low water pressure, simple to maintain
- Cons: needs loft space, slowest hot water recovery
- Best for: older properties with existing tanks and good loft access
- Typical install: £2,500 to £4,000
Most Kent homes I survey are good combi candidates. The exceptions are 3+ bathroom houses, properties with weak mains pressure, and homes where the existing cylinder system works perfectly and the owner just wants a swap.