A method of detecting a fault in a device is described. The method comprises receiving an energy consumption signal for the device, the energy consumption signal indicating a varying energy consumption of the device over time during operation of the device. A basis function is selected, the basis function defining a signal pattern associated with a known fault type. A correlation between the basis function and the energy consumption signal is evaluated. Presence of an operating fault in the device is determined in dependence on the correlation, and an output is generated based on the determination.