The NEMA 5-15 plug has two flat parallel blades like NEMA 1-15, but also adds a ground (earth) pin.It is rated 15 A at 125 volts. The ground pin is longer than the line and neutral blades, so the device is grounded before the power is connected. Both current-carrying blades on grounding plugs are normally narrow, since the ground pin enforces polarity. NEMA 1-15 plugs are also compatible with NEMA 5-15 sockets.

The 5-15 socket is standard in Canada, the United States, Mexico and Panama. It is also used in Central America, the Caribbean, northern South America (Colombia, Ecuador, Venezuela and, as a legacy, parts of Brazil), Japan, Taiwan, the Philippines and Saudi Arabia. This socket is recommended in IEC standard 60906-2 for 120 volt 60 Hz installations. Looking directly at a NEMA 5-15 socket with the earth at the bottom, the neutral slot is on the left, and the line slot is on the right. Sockets may be installed in any orientation.