Point-of-use water heaters: Point-of-use water heaters are also known as "tankless" heaters because they have no (or only a tiny) storage tank. They are relatively small units that provide hot water on demand. They use gas or electricity for fuel, and can be installed near demand points, such as under kitchen sinks. They are often more expensive than a conventional water heater, but can cost less to operate since they don't maintain a tankfull of hot water when not in use. A tankless heater typically provides 1-2 gallons of hot water per minute. Before installing a tankless water heater in your home, make sure its reduced capacity will be adequate for your needs.
Solar water heaters: A solar water heater typically includes collectors mounted on the roof or in a clear area of the yard, a separate storage tank near the conventional heater in the home, connecting pipe, and a controller. Solar water heaters can reduce the annual fuel cost of supplying hot water to your home by more than half. Throughout the year, the solar system preheats the water before it reaches the conventional water heater. During the summer, it may provide all the required heat.
Desuperheaters: A desuperheater is an attachment to your air conditioner or heat pump that allows waste heat from that device to help heat domestic water. In hot climates, a desuperheater can provide most of a home's hot water needs during the summer.