System for controlling voltage supply to a portion of a distribution grid. The portion of the grid includes a substation providing one or more transformers operable to increase or decrease the voltage supplied to consumers within the portion of the grid. The voltage control system providing a data set can include a previously measured power consumption associated with previously measured values of (a) property(ies) for a portion of the grid, the property(ies) being one of voltage, current, frequency or load, or a combination thereof. The voltage control system can provide a measurement device to measure the property(ies) supplied within the portion of the grid. The voltage control system can provide a processing device to determine from the previously measured values of the property(ies) in the data set a most likely effect of altering the value of the property(ies) from a first value to a second value, on the power consumption.