Power consumption is a primary concern for wireless sensor networks. In order to reduce the use of batteries in the nodes, energy harvesting technologies have been considered. However, most of the existing solutions rely on a single energy source, thus potentially reducing the sensor sustainability. In this paper, we present a circuit that switches between multiple heterogeneous energy sources, and uses a single power conditioning block. A prototype has been developed and validated with an existing wireless sensor. Measurements show that switching between energy sources can efficiently combine two energy sources in order to increase device autonomy and/or quality of service.