In operating mode M2, two electric heating elements are supplied with PV surplus power one after the other continuously. The upper heating element takes priority. The goal is to reach the desired temperature at the tap point as quickly as possible before the additional surplus heats the remaining storage content. Once the upper heating element reaches the target temperature, the lower heating element is supplied. If no my-PV temperature sensor is used, the switch is done through the thermostats of the heating elements, and the AC•THOR regularly checks if the upper heating element is available again. If the my-PV temperature sensor is used, the switch occurs when the temperature at the sensor reaches the set maximum value.