A combined seat heater and capacitive occupancy sensor comprises a heater network including a heating element (11) and a capacitive sensing circuit connected to the heating element to sense a capacitive load. A first and a second interface are provided for connecting the heating element to a first and a second terminal of a power source, respectively. Each interface comprises electronically controlled switches (3, 5; 4, 6) arranged in series and defining an intermediate node (20; 21). An oscillator (8) is AC-coupled to the intermediate nodes to apply an oscillating voltage thereto. A current measuring means (9), AC-coupled between the oscillator and the heating element, keeps the AC-potential of the heating element at least substantially equal, in amplitude and phase, to the oscillating voltage on the intermediate nodes and to derive the capacitive load from a thus resulting current flowing into the heating element.