During the transition periode in spring and autumn the solar heater generates more than enough warm water, while your heating is still running a little bit. In case of a adequate temperature regulator / valve controller the cold side of the room heating cycle can be warmed up using the heat exchanger inside the warm water tank. 

To do so the MED_HM-1 shows all eight relevant temperatures of solar heater and room heating on a 4" TFT touch display with fast micro controlle. Regarding the measured temperatures the room heating will be supported or not. In germany the sun is shining from march to october / november !