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Combi Boiler Review: Worcester 25Si Compact

As a leading brand for the domestic combi boiler, Worcester offers the industry unrivalled standards in manufacturing. Worcester combi boilers are highly efficient central heating systems and water heaters in a singular fixture. Hot water cylinders and cold storage tanks are not needed as the combi boiler immediately heats the water.

The 25Si compact combi is often the ideal choice for apartments or medium properties servicing 1 main bathroom. The compact size also means it easily fits unobtrusively in a kitchen cupboard. Worcester Si compact combi boilers fit out of sight in properties for hassle free installation.

worcester 25si compact combi 1678 0 1454922395000

Key Features

The compact features significantly smaller dimensions; 690mm (h) x 390mm (w), 280mm (d). The Worcester 25Si compact features significantly smaller dimensions to make storing the unit in a discrete cupboard easier. The reduced size has had no effect on the performance as the 25Si equals the previous Si boilers.

The 25Si compact combi boiler is also available in a choice of models depending on the fuel supply you require; this includes Natural Gas or LPG fuel.

The 25Si provides warmth on demand with 24kW power. Worcester created the Si series specifically for properties with a moderate to high demand for hot water with a flowrate of 10.2 litres per minute. The Worcester 25Si combi also comes with a convenient 5 year warranty with the manufacturer.


This combi boiler range is highly efficient. The Worcester Si Compact has been awarded with the SEDBUK A-rating, meaning this series functions at efficiency levels of over 90%.

The reduced size has had no effect on the performance as the 25Si equals the previous Si boilers.


The 25Si compact combination boiler provides swift installation for qualified engineers as it can be pre-plumbed out of the box.

Heating Control Compatibility

Worcester Combi Boilers offer a choice of compatibility with a variety of heating controls. This includes a range of brands, such as the Worcester Wave, Honeywell and Heatmiser smart thermostats. These are available in boiler packs which also contain a compatible flue.