Power windows or electric windows are automobile windows which can be raised and lowered by depressing a button or switch of some sort, as opposed to using a hand-turned crank. The power moonroof, a transparent, retractable sunroof, may be considered as an extension of the power window concept.
The first electric power windows were introduced around 1941 by Lincoln.  These are driven by a small electric motor inside the door and have come to be universal in the industry. Prior to that date, in the few vehicles offering this feature, the windows were driven by hydraulics or off the engine vacuum. In the 1950s, electric power was applied to the tailgate window in many station wagons.
In a typical installation, there is an individual switch at each window, and a set of switches in the driver's door so the driver can operate all the windows. However, some models have used switches located in the center console, where they are accessible to all the occupants. In this case, the door-mounted switches can be omitted.
Power windows are usually inoperable when the car is not running, as the electrical system is not live after the ignition is turned off. However, many modern cars have a time delay feature, first introduced by Cadillac in the 1980s, called retained accessory power. This allows operation of the windows and some other accessories for ten minutes or so after the engine is stopped. Another fairly recent innovation, pioneered by Nissan at about the same time, is the express-down window, which allows the window to be fully lowered with one tap on the switch, as opposed to holding the switch down until the window retracts.
Power windows have come under some scrutiny after several fatal accidents in which children's necks have become trapped, leading to suffocation. Some designs place the switch in a location on a handrest where it can be accidentally triggered by a child climbing to place his or her head out of the window. To prevent this, many vehicles feature a driver-controlled lockout switch, preventing rear-seat passengers (usually smaller children) from accidentally triggering the switches.
The American National Highway Traffic Safety Administration claims to be working on power window safety regulations, but has not established a date for their introduction.