A virtual power station for providing electrical power via an electrical power distribution network (40, 50) to one or more power consuming devices, the virtual power station including: one or more electrical power generators; at least one responsive load control having a respective one or more power consuming loads, the responsive load control being adapted to control power consumption in the one or more loads with respect to: i) a monitored physical variable of the electrical power distribution network (40, 50) and/or ii) control signals communicated to the responsive load control, the virtual power station being characterised in that, the at least one responsive load control being further adapted to cause the one or more power consuming loads to execute in a coordinated manner a response signature consisting of a small short term perturbation in the power consumption of said one or more power consuming loads; and in that it further includes: one or more power consumption monitors for monitoring changes in the power consumption of the power consuming loads during execution of the response signature by the power consuming loads; and a controller adapted to receive load data representative of monitored changes in the power consumption of the power consuming loads during execution of the response signature in a coordinated manner, the controller being further adapted to determine from said load data an available responsive load capacity. one or more electrical power generators; at least one responsive load control having a respective one or more power consuming loads, the responsive load control being adapted to control power consumption in the one or more loads with respect to: i) a monitored physical variable of the electrical power distribution network (40, 50) and/or ii) control signals communicated to the responsive load control, the virtual power station being characterised in that, the at least one responsive load control being further adapted to cause the one or more power consuming loads to execute in a coordinated manner a response signature consisting of a small short term perturbation in the power consumption of said one or more power consuming loads; and in that it further includes: one or more power consumption monitors for monitoring changes in the power consumption of the power consuming loads during execution of the response signature by the power consuming loads; and a controller adapted to receive load data representative of monitored changes in the power consumption of the power consuming loads during execution of the response signature in a coordinated manner, the controller being further adapted to determine from said load data an available responsive load capacity. one or more power consumption monitors for monitoring changes in the power consumption of the power consuming loads during execution of the response signature by the power consuming loads; and a controller adapted to receive load data representative of monitored changes in the power consumption of the power consuming loads during execution of the response signature in a coordinated manner, the controller being further adapted to determine from said load data an available responsive load capacity.