Why Do Appliance Plugs Get Hot?

People use electric appliances every day to help them accomplish household tasks quickly. An appliance receives electrical power through its plug in a household electrical outlet. Because some of the power the appliance receives is lost to waste heat, the plug may become warm to the touch. A plug that is hot to the touch, however, may pose a danger to you and your home.

Electric devices that have motors use electric current to create electromotive force. Electronic devices – which include all devices that have a transistor – use both voltage and current to control computer microchips, amplify alternating current (AC) signals or convert AC power into direct current (DC) power. When electric current passes through an electric or electronic component, part of the current, or power, is lost to waste heat. Because all materials that conduct electric current provide some electrical resistance, even highly conductive materials such as electrical wire and the metal prongs on a power plug generate some waste heat.

While it is normal for an appliance plug to become warm, it is abnormal for such a plug to get hot. Heat generated from passing electric current through an electrically resistive body is called "ohmic heating." If a plug or electrical outlet is loose, the electric current from that plug or outlet has to pass through an area with high electrical resistance to complete the circuit. To provide enough power to operate the appliance, more power must pass through the plug or outlet to reach the appliance. Most of the increased power is converted to waste heat, and the plug becomes hot to the touch. Internal electrical faults in the appliance, such as a short circuit or improperly grounded electrical connection, also can cause the device to draw more power than necessary and excess heating.

A plug that is hot to the touch may pose fire and electrical shock hazards. If an overheated plug is near flammable materials, such as curtains, wood furniture or paper, then the plug can ignite those materials, starting a fire. Similarly, overheated plugs can damage the insulating material around the plug's prongs or electrical cord wires. Damaged insulation can expose the metal conductors in an electrical cord, causing a shock hazard.

If an electric appliance's plug is hot to the touch, turn off the circuit breaker — or remove the fuse — to the electrical outlet into which the appliance is plugged. Wait several minutes for the plug to cool before removing it from the electrical outlet. Do not plug the appliance into another outlet. If a loose outlet appears to be the problem that caused the plug to overheat, you may wish to call an electrician to examine the outlet and replace it if necessary.