Combination boiler

Combination boilers, or ‘combi boilers’, supply central heating and hot water directly from the water supply, without the need for a water tank or hot water cylinder.

Because hot water is supplied ‘instantaneously’ rather than being stored and then used, they can provide unlimited hot water on demand, and are useful where there is limited space availability. This can be a more efficient type of boiler, as the hot water is used immediately, rather than being stored.

However, as there is no reservoir of hot water, when there are multiple simultaneous uses, the pressure may drop. This may make them best suited to smaller, lower-occupancy properties.

The English Housing Survey, Headline Report, 2020-21, published by the Department for Levelling Up, Housing and Communities in 2021, defines a combination boiler as a boiler that: ‘provides hot water or warm air for space heating and can provide hot water on demand negating the need for a storage cylinder, therefore requiring less space.’

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