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.



Ultimate 30c Efficiency

SAP seasonal efficiency


Rating band

Band B


ManufacturerGlow-worm Boilers
ModelUltimate 30c
Fuel TypeGas
Flue TypeRoom-Sealed
FanFan Assisted
Output (kW)24.2 - 24.2
Boiler IDGC No 47-019-20
Manufactured From/To2013 - current


The Glow-worm Ultimate 30c is a 'B' rated boiler which has good efficiency of 89.8%.

The Ultimate 30c is a Condensing Combi boiler with a maximum power output of 24.2kw that uses Gas as its fuel source.

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


Similar Glow-worm Boilers to the Ultimate 30c
(Condensing Gas Combi)

Results ordered by efficiency. Some models may be obsolete.

Glow-worm Xtramax HE

90.6% Efficient

Most Efficient Combi Gas Boilers

Vaillant ecoTEC plus 937

91.5% Efficient

Alpha CD50

91.2% Efficient