The electricity generated by a power plant and delivered to your home by your local utility is called alternating current (AC) because it flows alternatively, first in one direction then in the opposite, completing 60 cycles second. Batteries produce DC or direct current. From the power plant, current travels over high-voltage transmission lines to substations, where transformers reduce the voltage for distribution to local lines. Neighborhood transformers lower voltage to 120 and 240 volts for home delivery.