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.



COD C2 20/26 Efficiency

SAP seasonal efficiency


Rating band

Band A


ManufacturerGEM Boilers
ModelCOD C2 20/26
Fuel TypeOil
Flue TypeOpen or Room-Sealed
FanFan Assisted
Output (kW)20 - 26
Boiler ID
Manufactured From/To2007 - current


The GEM COD C2 20/26 is an 'A' rated boiler which has an excellent efficiency of 90.0%.

The COD C2 20/26 is a Condensing Combi boiler with a maximum power output of 26kw that uses Oil 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 GEM Boilers to the COD C2 20/26
(Condensing Oil Combi)

Results ordered by efficiency. Some models may be obsolete.

GEM CC4 35/41

90.2% Efficient

GEM COD C4 35/41

90.2% Efficient

GEM COD C3 26/35

90.2% Efficient

GEM CC3 26/35

90.2% Efficient

Most Efficient Combi Oil Boilers