Boiler Efficiency Ratings

Compare new boilers and assess whether your current boiler would be better off being replaced

Our boiler efficiency tables provided by SEDBUK (the seasonal efficiency of domestic boilers in the UK) provide a guide of how effective your boiler is at turning fuel into heat.

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 0333 230 5216 for a no-obligation quote, alternatively visit Boiler Guide to request quotes from independent local and regional heating engineers.



Optimax HE Plus 25 S Efficiency

SAP seasonal efficiency


Rating band

Band A


ManufacturerFerroli Boilers
ModelOptimax HE Plus 25 S
Fuel TypeGas
Flue TypeRoom-Sealed
FanFan Assisted
Output (kW)24.6 - 24.6
Boiler ID41-267-32
Manufactured From/To2009 - current


The Ferroli Optimax HE Plus 25 S is an 'A' rated boiler which has an excellent efficiency of 90.5%.

The Optimax HE Plus 25 S is a Condensing Conventional boiler with a maximum power output of 24.6kw that uses Gas as its fuel source.

As this boiler is 'A' rated it will provide efficient heating and subsequently reduce fuel bills and carbon dioxide emissions.


Similar Ferroli Boilers to the Optimax HE Plus 25 S
(Condensing Gas Conventional)

Results ordered by efficiency. Some models may be obsolete.

Ferroli Maxima 35S

91.0% Efficient

Ferroli Optimax HE 31 S

90.6% Efficient

Ferroli Optimax HE 25 S

90.5% Efficient

Most Efficient Conventional Gas Boilers

Baxi Solo 15 HE A

91.3% Efficient

Main 15 HE A

91.3% Efficient

Potterton Promax SL 15

91.3% Efficient

Potterton Gold H 15

91.3% Efficient