Methods and systems for controlling a reactive power contribution to reactive power flowing in an electricity distribution network, so as to optimize this reactive power flow are described. A reactive power characteristic of electrical power flowing in the electricity distribution network is detected at a power device. The reactive power characteristic relates to a reactive power component of electricity flowing in the network. On the basis of the detected reactive power characteristic a reactive power contribution to the electricity distribution network is controlled so as to adjust a value of the detected reactive power characteristic. This enables individual power consumption and/or provision devices to react autonomously to local variations in the electricity distribution network, and to provide a reactive power contribution, to drive the detected reactive power characteristic towards a desired value.