Distribution voltage is typically AC (alternating current).
AC is used for power distribution because it can be easily transformed to higher or lower voltages using transformers. This allows for efficient long-distance transmission at high voltages and reduction to safer, lower voltages for end-users.
Transmission lines carry high-voltage AC, usually in the range of 110 kV to 765 kV, to minimize power losses. Substations then step down the voltage for local distribution, typically to 4 kV to 34.5 kV. Finally, distribution transformers further reduce the voltage to the standard 120/240 V for residential and small commercial use.
AC has been the standard for power distribution since the late 19th century, largely due to the influence of Nikola Tesla and the Westinghouse Electric Company. While high-voltage DC (HVDC) transmission is used in some special applications, such as undersea cables or long-distance point-to-point transmission, AC remains the dominant form of distribution voltage.