Abstract: This disclosure relates to determining a context of a mobile device. A processor receives from one or more first sensors first sensor data in relation to the context. The processor then selects from multiple second sensors one or more selected sensors based on the first sensor data and based on an energy cost value associated with each of the multiple second sensors, the energy cost value being indicative of energy consumed when requesting data from each of the multiple second sensors. Next, the processor receives from the one or more selected sensors second sensor data and determines the context of the mobile device based on the first sensor data and the second sensor data. This reduces the overall energy consumption and therefore extends the battery life of the mobile device while still providing an accurate context determination.