AC voltage is the standard for electrical transmission due to its inherent ability to be easily converted to different voltage levels. This is a critical factor for minimizing power loss over long distances.

The primary reason for this is the use of transformers. Transformers are devices that can efficiently "step up" or "step down" AC voltage. By stepping up the voltage to a very high level for long-distance transmission, the current is simultaneously reduced. Since power loss during transmission is proportional to the square of the current (Ploss=I2R), a small reduction in current leads to a significant decrease in energy waste. At the destination, transformers "step down" the voltage to safe levels for distribution to homes and businesses.

While DC (Direct Current) transmission is also used, particularly for very long distances or submarine cables where it offers certain advantages like lower line losses and no "skin effect," the widespread use of transformers makes AC the more practical and economical choice for the majority of power grids worldwide.

This was a key point in the historical "War of the Currents" between Thomas Edison (who championed DC) and Nikola Tesla/George Westinghouse (who championed AC). AC ultimately prevailed because of its superior efficiency and cost-effectiveness for long-distance transmission, thanks to the transformer.