An apparatus for selectively stepping up/down the voltage applied from an input to any load in an alternating current power system. The apparatus includes an auto transformer having a series winding with a plurality taps for the selection of different output load voltages and a common winding. The series winding being connected between said input of the alternating current power system and said common winding. The common winding being connected between the series winding and common or neutral terminal of an alternating current power system. The load is being connected between one tap of the series winding and the common or neutral terminal of the alternating current power system. A pair of switching or solid state switching devices, the first switching device being connected between the autotransformer common winding and the common or neutral terminal of an alternating current power system, and one terminal of the second switching device is connected between the auto transformer series and common winding and the second terminal of the switching device is connected between the auto transformer common winding and the first switching device. The paid of switching or solid state switching devices being configured for disconnecting said common winding of the auto transformer from the common or neutral terminal of an alternating current power system and shorting the common winding in a first position and opening the shorted common winding and connected said auto transformer common winding to the common or neutral terminal of an alternating current power system in a second position.