The energy efficiency categories for heating heat pumps are based on a seasonal coefficient of performance (SCOP). This depends firstly on the climatic region and secondly on the potential heating system. Europe is divided for this purpose into three climatic regions. For radiators and underfloor heating systems, the different flow temperatures and possible energy efficiency categories are shown on the Energy Labels.
Stand-alone heat pumps are rated a maximum of A++ and as part of integrated system can be rated as an A+++. Heating boilers (oil, gas, bio-mass) on the other hand are rated A at best, and in some cases as low as C or D. If the end-user is interested in top efficiency that is A+++ energy class rating they should look at heat pump as part of an integrated system.