In contrast, storage water heaters last 10–15 years. They also have easily replaceable parts that may extend their life by many more years.

Most tankless water heaters have a life expectancy of more than 20 years. The initial cost of a tankless water heater is greater than that of a conventional storage water heater, but tankless water heaters will typically last longer and have lower operating and energy costs, which could offset their higher purchase price. In some cases you may be able to achieve even greater energy savings if you install a demand water heater at each hot water outlet. They can be 8%–14% more energy efficient for homes that use a lot of hot water - around 86 gallons per day.

Booster for a solar water heating system.įor homes that use 41 gallons or less of hot water daily, demand water heaters can be 24%–34% more energy efficient than conventional storage tank water heaters.

Booster for appliances, such as dishwashers or clothes washers.

Other applications for demand water heaters include the following:

You can also install separate tankless water heaters for appliances - such as a clothes washer or dishwater - that use a lot of hot water in your home. However, additional water heaters will cost more and may not be worth the additional cost. To overcome this problem, you can install two or more tankless water heaters. For example, taking a shower and running the dishwasher at the same time can stretch a tankless water heater to its limit. Sometimes, however, even the largest, gas-fired model cannot supply enough hot water for simultaneous, multiple uses in large households. Gas-fired tankless water heaters produce higher flow rates than electric ones. Typically, tankless water heaters provide hot water at a rate of 2–5 gallons (7.6–15.2 liters) per minute. However, a tankless water heater's output limits the flow rate. You don't need to wait for a storage tank to fill up with enough hot water. As a result, tankless water heaters deliver a constant supply of hot water.

When a hot water faucet is turned on, cold water flows through a heat exchanger in the unit, and either a natural gas burner or an electric element heats the water. Tankless water heaters heat water instantaneously without the use of a storage tank.

Modern house water tank design