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.



Heatslave 9.24rsf Efficiency

SAP seasonal efficiency


Rating band



ManufacturerWorcester Boilers
ModelHeatslave 9.24rsf
Fuel TypeGas
Flue TypeRoom-Sealed
FanFan Assisted
Output (kW)24 - 24
Boiler ID4731103
Manufactured From/ToUnknown - 1989


The Worcester Heatslave 9.24rsf is unrated, this probably means it's obsolete or very old.

The Heatslave 9.24rsf is a Non-Condensing Combi boiler with a maximum power output of 24kw that uses Gas as its fuel source.

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


Similar Worcester Boilers to the Heatslave 9.24rsf
(Non-Condensing Gas Combi)

Results ordered by efficiency. Some models may be obsolete.

Worcester 24 Cdi BF

79.4% Efficient

Worcester Highflow 400 RSF

79.2% Efficient

Worcester 35 Cdi RSF

78.9% Efficient

Most Efficient Combi Gas Boilers

Vaillant ecoTEC plus 937

91.5% Efficient

Alpha CD50

91.2% Efficient