A power control device prevents unauthorized and unwanted use of electrical devices by locking the plug of the electrical device in the power control device, when the current flowing through the power control device is stopped. The device includes a switch, moveable between on and off conditions by moving a slide lock or bolt, typically by rotating a key in a locking structure. When the slide lock has moved into contact with the switch, such that it is in an off-condition and current is not flowing through the power control device, the slide lock has also locked the plug in the power control device. The electrical device is temporarily inoperable and can not resume normal operation until the power control device is unlocked.