A system comprises: at least one heat exchange panel (700) comprising: a main body (100) comprising a sealed cavity in which is provided a fluid in both liquid and gas phases and being configured to communicate heat energy by allowing evaporation of the liquid at one location and condensation of the liquid at a different location in the cavity; and at least a first heat exchanger part (130, 210a, 211a) including an inlet and an outlet for allowing the passing of fluid through the heat exchanger, the first heat exchanger part being thermally coupled to the heat spreading part so as to communicate heat energy between fluid flowing through the first heat exchanger part and the heat spreading part and thus the environment in which the heat spreading part is present. A controller is configured to cause control of pumps and valves to as to cause the system to operate in a number of different modes of operation, wherein the system is operable in an active heating mode of operation in which the controller controls the heat pump, the one or more fluid pumps and the valves to provide the system with: a first fluid circuit in which fluid is pumped through the heat exchange panel and a first side of the heat pump, a second fluid circuit in which fluid is pumped through the heat tank and the second side of the heat pump, and transfer by the heat pump of heat energy from the first fluid circuit to the second fluid circuit.