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.



Heat Slave 15/19.OSO Efficiency

SAP seasonal efficiency


Rating band

Band C


ManufacturerWorcester Boilers
ModelHeat Slave 15/19.OSO
Fuel TypeOil
Flue TypeOpen
FanFan Assisted
Output (kW)19 - 19
Boiler IDC14769/3-1
Manufactured From/To1997 - current


The Worcester Heat Slave 15/19.OSO is a 'C' rated boiler with an efficiency of 82.8%.

The Heat Slave 15/19.OSO is a Non-Condensing Combi boiler with a maximum power output of 19kw that uses Oil as its fuel source.

Although a 'C' rated boiler is not as efficient as many other modern boilers it's still pretty good, only a marginal reduction in fuel bills and carbon dioxide emissions would be observed by replacing it.


Similar Worcester Boilers to the Heat Slave 15/19.OSO
(Non-Condensing Oil Combi)

Results ordered by efficiency. Some models may be obsolete.

Most Efficient Combi Oil Boilers