AC could be considered more efficient for distribution and transmission purposes because it is easy to step up to high voltage levels (=> lower current for the same power transmission => lower resistive losses) using a transformer. However, for very long power transmission lines, at very high voltages, capacitive coupling of AC voltage to the earth, and skin effects can cause some additional losses. High-voltage DC links are used in a number of places for point-to-point transmission.
AC is preferred over DC because of the following reasons:
- Loss of power during transmission of current from the power generation plant to the grid is less in AC than in DC.
- AC can be easily transformed into DC with the help of rectifiers whereas in DC it is not possible.
- AC can be easily stepped up or stepped down by transformers, whereas in DC, it is impossible because transformers work on a changing emf principle.
- Generation of AC is cheaper than DC power.
- Induction motors work on AC power supply only.