Tankless Water Heaters

July 30, 2009



Due to their energy efficiency and compact design, tankless water heaters have become very popular. AAA AUGER promotes their use and requires that all of our licensed plumbers gain manufacturer’s certification (if offered) before installing any specific brand. If a tankless water heater is an option for you, there are many factors that should be carefully considered.

Why are tankless water heaters more energy efficient than conventional water heaters?

Conventional tank-type heaters heat water for future use. Because there may not be an immediate demand for the hot water, the heater uses additional energy to maintain the water’s temperature. Because tankless water heaters heat water upon demand, energy is not wasted maintaining the water’s temperature.

Why aren’t conventional water heaters obsolete?

Installation Cost

Tankless water heaters may not always be the most economical solution. Although tankless water heaters are more energy efficient, the initial investment may not be offset by the savings from operation. This is most prevalent in existing applications.

Tankless water heaters require a significantly higher power supply than conventional heaters. In gas fired applications, the entire gas system may require updating. In electrical applications, it may be necessary to install a high amp electrical service. Either case may substantially increase installation costs.

Most manufacturers require that a water softener be installed where hard water exists. Failure to do so will significantly decrease the life of the heater and may void the manufacturer’s warranty. Should a water softener be necessary, installation costs may increases substantially


Performance

Performance is another factor that should be considered. Tankless water heaters perform differently from conventional water heaters.

In a tankless water heater, as hot water is drawn, an inlet valve opens and allows water into the heat exchanger. The heat exchanger is designed much like an automotive radiator with water lines routed through fluted fins. Unlike a radiator designed to cool water, the heat exchanger is surrounded by a high powered heat source. Water, as it travels through the heat exchanger, is heated rapidly providing a semi-endless supply of hot water.

When selecting a tankless water heater, there are two factors that must be considered, the demand for hot water placed thereupon and the lowest ambient water temperature common to the area. Most tankless water heater manufacturers provide a graph that illustrates performance losses based upon these two factors.

Demand is calculated by water supply fixture units (WSFU’s). A fixture’s WSFU is directly proportional to its highest flow rate in gallons per minute (GPM). Therefore, to assure an adequate supply of hot water, the system’s WSFU’s must be figured as though all fixtures were running simultaneously.

Unfortunately, in many applications, multiple heaters may be required to assure ample supply. No matter the heater, performance losses should be expected when pushed to flow rate capacities. These performance losses result in diminished hot water volumes and/or decreased water temperatures. However, these limitations can often be avoided with little effort. Sometimes it simply comes down to changing personal habits; i.e. avoid showering while running the clothes washer.

What to do?

AAA AUGER encourages that tankless water heaters always be considered before conventional heaters. However, return on your investment may take many years to realize. Furthermore, when looking to upgrade, the heater may need to be replaced or may require major service at or before the break even point. Regardless, once installed, the savings in actual operational costs are significant. For those committed to energy conservation, there is no better choice.