These devices transform the direct current generated by a solar panel or electric car battery into the alternating current you expect from a wall socket.

FORBES: Magazine Article

Although they have not been found to cause any harm, the cables on conventional pylons, which transmit a three-phase alternating current, generate a strong electric field and a continuous buzz of low-frequency radio waves.

ECONOMIST: Monitor

Plug loads refer to electric power consumed by products through an ordinary alternating current plug socket.

FORBES: Energy Waste Rebounds: Top 10 Energy Pigs in the Plug

One of the considerations was the relative safety of direct current - the first electric chair seems to have been built (and then used) to prove that alternating current was more of a killer.

BBC: A universal plug socket... at last?