Boilers with a SEDBUK Band Rating of “D” have an efficiency value of between seventy-eight and eighty-two percent (78%-82%). If you have a Standard (non-condensing) GAS Boiler already installed & would like to check it’s SEDBUK SAP rating – please view the complete, full boiler list on the SEDBUK Band D (efficiency rating between 78%-82%) Boiler Ratings Page! HINT: Click the image (on the left!) to read more…