A power plug for coupling an electrical appliance to an electrical power supply, comprising: a current sensor, configured to measure current supplied through the plug to the electrical appliance; a voltage sensor, configured to measure voltage supplied through the plug to the electrical appliance; a processor configured to: determine power consumption data from data relating to the current and voltage measurements made by the current and voltage sensors; and monitor the performance of the electrical appliance using the power consumption data; and a transmitter, configured to transmit information relating to the performance of the electrical appliance.