How a combi boiler works
A combi (combination) boiler heats water on demand direct from the mains — no hot water cylinder, no cold water tank in the loft. Compact, efficient and popular in flats and smaller homes across Kingston and Twickenham.
How a system boiler works
A system boiler heats water and stores it in an unvented hot water cylinder, usually in an airing cupboard. Cold feed comes from the mains, no loft tank. Delivers strong flow to multiple bathrooms simultaneously — a common choice for family homes in KT areas like Surbiton, New Malden and Esher.
Combi pros and cons
Pros: no cylinder, less space needed, cheaper install, endless hot water on demand. Cons: flow drops if multiple taps or showers run at once, unsuitable for homes with 2+ bathrooms or low mains pressure.
System pros and cons
Pros: strong hot water flow to multiple outlets simultaneously, works well with low mains pressure, ideal for larger homes. Cons: needs cylinder space, cylinder heat loss, longer install time, higher upfront cost.
Which suits your home?
1–2 bedroom flat / small house, one bathroom: combi. 3+ bedroom house, 2+ bathrooms or high hot water demand: system. Existing tanks in the loft you want removed: often a system swap. We survey and quote for both across KT/TW.
Unsure which boiler suits your home? Book a free survey in KT/TW.
Call 07932 898534Frequently asked questions
Which is cheaper to install?
Combi swaps are typically £1,900–£2,500; system boiler installs with cylinder run £3,000–£4,500+. Full conversions cost more.
Which is more energy efficient?
Both modern A-rated boilers hit 92%+ efficiency. Real-world savings depend more on controls, insulation and household habits than boiler type.
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