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Ariston Clas 21 FF System Gas - Boiler Efficiency Ratings

Boiler Efficiency Rating

You can find out the energy efficiency of your boiler by checking its energy rating; you can do this now by selecting the make and model below.

A boiler’s energy rating is an indicator of its efficiency when used within an average domestic household. It's a great benchmark for comparing new boilers and can help you work out how much money you could save on energy bills if you replaced your current boiler with a more efficient model.

For new boiler installations call British Gas Boilers on 0333 230 5216 for a no-obligation quote. Alternatively visit Boiler Guide to request quotes from independent local and regional heating engineers.

Ariston Clas 21 FF System Efficiency

SAP seasonal efficiency80.4%
Rating bandBand D


ManufacturerAriston Boilers
ModelClas 21 FF System
Fuel TypeGas
Flue TypeRoom-Sealed
FanFan Assisted
Output (kW)24.2 - 24.2
Boiler ID41-116-27
Manufactured From/To2007 - 2008


The Ariston Clas 21 FF System is a 'D' rated boiler with an efficiency of 80.4%.

The Clas 21 FF System is a Non-Condensing Conventional boiler with a maximum power output of 24.2kw 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.

Similar Ariston Boilers to the Clas 21 FF System
(Non-Condensing Gas Conventional)

Results ordered by efficiency. Some models may be obsolete.

Most Efficient Conventional Gas Boilers