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Keston Thermomatic RSM25FB Gas - Boiler Efficiency Ratings

Boiler Efficiency Rating

You can check your boilers rating by selecting it's make and model below. Ratings are based on the SEDBUK Rating which is an indicator of its efficiency when used within an average domestic household, it's a great benchmark for comparing new boilers and also assessing whether your current boiler would be better off being replaced due to low efficiencies.

For new boiler installations call British Gas Boilers on 0800 327 7119 for a no-obligation quote, alternatively visit Boiler Guide to request quotes from independent local and regional heating engineers.

Keston Thermomatic RSM25FB Efficiency

SAP seasonal efficiency78.0%
Rating bandBand D


ManufacturerKeston Boilers
ModelThermomatic RSM25FB
Fuel TypeGas
Flue TypeRoom-Sealed
FanFan Assisted
Output (kW)28 - 28
Boiler ID
Manufactured From/To1988 - current


The Keston Thermomatic RSM25FB is a 'D' rated boiler with an efficiency of 78.0%.

The Thermomatic RSM25FB is a Non-Condensing Combi boiler with a maximum power output of 28kw that uses Gas as its fuel source.

Being a 'D' rated boiler it would be worthwhile replacing it with a higher efficiency 'A' rated boiler.

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