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.



iheat 25c Efficiency

SAP seasonal efficiency


Rating band

Band A


ManufacturerHalstead Boilers
Modeliheat 25c
Fuel TypeGas
Flue TypeOpen or Room-Sealed
FanFan Assisted
Output (kW)19.64 - 19.64
Boiler ID4726016
Manufactured From/To2008 - current


The Halstead iheat 25c is an 'A' rated boiler which has an excellent efficiency of 90.3%.

The iheat 25c is a Condensing Combi boiler with a maximum power output of 19.64kw 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 Halstead Boilers to the iheat 25c
(Condensing Gas Combi)

Results ordered by efficiency. Some models may be obsolete.

Halstead Eden CBX 32

90.8% Efficient

Halstead Ace HE35

90.6% Efficient

Halstead Eden cb

90.3% Efficient

Halstead Eden CBX 38

90.3% Efficient

Most Efficient Combi Gas Boilers

Alpha CD50

91.2% Efficient