Controlling groups of energy producing and/or consuming devices in an electricity network

A regulated group of energy producing and/or consuming devices in an electricity network is controlled by applying one or more trigger levels that, when exceeded, cause the devices to either stop or start, reduce or increase producing or consuming power, or to be disconnected. The trigger levels may be fixed or variable sequential trigger levels, and the devices may be individually and sequentially disconnected from the network. Reset trigger levels may be provided which when breached cause the energy producing and/or consuming devices to restart producing and/or consuming power. The trigger levels may be applied according to monitored parameters.