Rheem, Jacuzzi and EcoSmart offer tankless water heaters. These units heat water on demand and eliminate a storage tank. They are available in point-of-use devices that install under the sink and whole-house models.
Tankless water heaters reduce the energy lost by hot water storage tanks. These units have water flow sensors that determine when to heat the water. They usually supply 2 to 5 gallons of water per minute, with electric systems at the low end of the scale and gas ones toward the high end. At this rate, some tankless models are unable to supply enough water to operate a shower and dishwasher simultaneously, according to the U.S. Department of Energy.
The actual savings the homeowner experiences using a tankless system depends on his family's particular pattern of usage. In homes using 41 or fewer gallons daily, the U.S. Department of Energy estimates a 24 to 34 percent savings when compared to using a whole house system. For homes that use more water, the savings decreases. Installing point-of-use water heaters for each outlet increases the savings to up to 50 percent for homes with tankless systems.
In the United States, initial installation costs for tankless water heating systems are higher. However, the life expectancy for the tank-type system is significantly shorter than that of the tankless system.