A power supply is a device or source of electrical energy. The term power supply can mean different things in different contexts. For instance, a power supply in a desktop computer converts a 120-volt AC current to various other low voltage DC currents. While doing electrical wiring in your home, the term power supply usually references your service panel where the electrical power enters your home. Power supplies could also mean a device that converts one form of energy (e.g., mechanical, chemical, solar) to electrical energy.