Demand Water Heaters
Demand Water Heaters do not contain a storage tank like conventional water heaters. A gas burner or electric element heats water only when there is a demand for hot water. Hot water never runs out, but the flow rate (gallons of hot water per minute) may be limited. By eliminating standby losses from the tank, energy consumption can be reduced by 10-15%. Before rushing out to buy a demand water heater, be aware that they are not appropriate for every situation. Here are some of the factors to consider:
* Do you use hot water efficiently? Have you installed modern, low-flow faucets and showerheads? Tankless water heaters perform much better when coupled with efficient uses.
* Consider your water distribution system. If the hot water uses in your home are relatively close together, with short hot water lines between them, a tankless system may work for you. In many U.S. homes, water uses are widely spaced at opposite ends of the house. If this is the case in your home, a tankless system may not meet your needs.
* If you have installed high efficiency fixtures and your water lines are not too long, consult an experienced contractor to find out if your gas supply is adequate and proper venting is feasible.
* Finally, residential wiring generally will not support a tankless electric water heaterwith large enough capacity to serve multiple uses. If you rely on electricity to heat your water, a tankless system is unlikely to meet your needs. At most, an electric unit may be appropriate for small applications, such as a remote bathroom without a bath tub.
 Noritz NR111-DV-LP Tankless Water Heater US $1,637.44 
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 Noritz NR111-DV-NG Tankless Water Heater US $1,637.44
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 Noritz NR111-SV-NG Tankless Water Heater US $1,637.44
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 Noritz NR66-SV-NG Tankless Water Heater US $761.25
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If you choose a tankless unit, look for a gas-fired model eligible for 2009 federal tax credits, at least an Energy Factor (EF) of 0.80. To learn more about tankless water heaters, visit these manufacturers' sites.