Most self-winding garden hose reels use a water or battery-powered motor to turn a reel, winding the hose onto it. A guide keeps the hose from becoming tangled, and the entire thing is usually housed in a box. A short hose connects the reel to the tap.
Battery-operated reels rely on electricity to power the internal mechanism. If the battery fails, most can be operated manually, but the internal motor or the design may make it difficult to use. Water-powered models use an engine operated by pistons to turn the reel and wind up the hose. As the hose retracts, water is expelled either from the hose or another external tube. Some of these models do not have a hand crank to use if the mechanism fails. Some users may be concerned about the amount of water required to power the mechanism, which can be several gallons, but they can collect the water for use in their gardens.
Self-winding hose reels contain the hose in a container that protects it from harmful UV rays. Gardeners who use very long or heavy hoses, or who suffer from mobility problems, appreciate the convenience they provide. Some newer models feature a remote-control so the user can turn on the hose from indoors, or a timer that turns the water on automatically.