A method of aligning data measured by monitoring devices (M, 128, 130) coupled to a power monitoring system, characterized in that it comprises: receiving, at a controller remote from said monitoring devices, reference signal data from a reference monitoring device, said reference signal data representing at least frequency or amplitude variations in current or voltage from an electric grid measured by said reference monitoring device for a predetermined number of cycles of said current or voltage sensed by said reference monitoring device, said reference monitoring device storing a reference count associated with each of said cycles of current or voltage sensed by said reference monitoring device; receiving, at said controller, second signal data from at least a second monitoring device, said second signal data representing at least said frequency or amplitude variations in current or voltage from said electric grid measured by said second monitoring device for a predetermined number of cycles of said current or voltage sensed by said second monitoring device, said second monitoring device storing a second count associated with each of said number of cycles of current or voltage sensed by said second monitoring device; and automatically aligning said reference signal data with said second signal data to a common reference point in said respective current or voltage sensed by said reference monitoring device and said second monitoring device by: computing a plurality of correlation coefficients each produced by a cross-correlation algorithm (400, 500, 600) based on at least part of said reference signal data and at least part of said second signal data until one of said correlation coefficients produced by said cross-correlation algorithm satisfies a criterion; and responsive to said one of said correlation coefficients satisfying said criterion, associating said reference count associated with said common reference point with said second count associated with said common reference point. receiving, at a controller remote from said monitoring devices, reference signal data from a reference monitoring device, said reference signal data representing at least frequency or amplitude variations in current or voltage from an electric grid measured by said reference monitoring device for a predetermined number of cycles of said current or voltage sensed by said reference monitoring device, said reference monitoring device storing a reference count associated with each of said cycles of current or voltage sensed by said reference monitoring device; receiving, at said controller, second signal data from at least a second monitoring device, said second signal data representing at least said frequency or amplitude variations in current or voltage from said electric grid measured by said second monitoring device for a predetermined number of cycles of said current or voltage sensed by said second monitoring device, said second monitoring device storing a second count associated with each of said number of cycles of current or voltage sensed by said second monitoring device; and automatically aligning said reference signal data with said second signal data to a common reference point in said respective current or voltage sensed by said reference monitoring device and said second monitoring device by: computing a plurality of correlation coefficients each produced by a cross-correlation algorithm (400, 500, 600) based on at least part of said reference signal data and at least part of said second signal data until one of said correlation coefficients produced by said cross-correlation algorithm satisfies a criterion; and responsive to said one of said correlation coefficients satisfying said criterion, associating said reference count associated with said common reference point with said second count associated with said common reference point. computing a plurality of correlation coefficients each produced by a cross-correlation algorithm (400, 500, 600) based on at least part of said reference signal data and at least part of said second signal data until one of said correlation coefficients produced by said cross-correlation algorithm satisfies a criterion; and responsive to said one of said correlation coefficients satisfying said criterion, associating said reference count associated with said common reference point with said second count associated with said common reference point.