Launch Slideshow

On Demand

As more builders look for energy-efficient technology, tankless water heaters may one day be the norm, rather than the exception, in homes nationwide.

On Demand

As more builders look for energy-efficient technology, tankless water heaters may one day be the norm, rather than the exception, in homes nationwide.

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    Grand Hall. The Eternal GU32 hybrid water heating system combines the best attributes of tank and tankless systems, with an inverted-infrared heat burner that uses thermal activation like a tank and flow activation like a tankless. The system uses a counter-flow design and multi-pass heat exchanger technology to maintain an 86% thermal efficiency rating with consistent pressure. The unit operates at a lower emission rate than traditional tank and tankless water heaters, says the company. The system’s nitrogen oxide emission is less than 5 parts per million. 877.934.7455. www.eternalwaterheater.com  
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    Stiebel Eltron. The electric Tempra whole-house series comprises six tankless water heater models, from 12 kW to 36 kW, that can be installed in homes with one to four bathrooms. The smallest capacity unit has one heating module, the mid-range models have two heating modules, and the largest capacity units have three heating modules, which are all wired back separately to the electric panel. The temperature and flow sensors feed their readings into the water heater’s microprocessor control, and the microprocessor prevents the water temperature from deviating from the set point. The tankless water heaters, which the company says are nearly 100% efficient, save 15% to 20% on water heating costs compared to a tank water heater. Energy factor: 0.99. 800.582.8423. www.stiebel-eltron-usa.com  
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    Chronomite. The electric Insta Flow point-of-use tankless water heaters are 98% efficient, says the firm. Digital microprocessor technology controls the temperature of the water, and the temperature can be pre-set to prevent scalding without mixing valves. The units come in three different capacities­—Insta Temp, Insta Flow, and Insta Flow Micro—and are also available in a wide range of models to fit the desired application. 800.447.4962. www.chronomite.com
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    Takagi. The gas-fired TK-3 Pro is designed to withstand space-heating and domestic recirculation systems in residential applications. It starts heating water at flow rates as low as 0.5 gallons per minute, but it can generate an unlimited supply of hot water at a maximum flow rate of 7 gallons per minute. The unit measures 13.8 inches wide and weighs 40 pounds. It can be installed inside or outside and can be direct-vented. Energy factor: Natural gas: 0.827; LP: 0.833. 888.882.5244. www.takagi.com
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    Rheem. The RTG-66DV gas direct-vent, tankless water heater is designed for homes with two or three bathrooms. The unit measures 25 1/2 inches high, 13 1/2 inches wide, and 10 inches deep. The concentric venting system simplifies installation by expelling the byproducts of combustion through a 3-inch exhaust pipe inside the 5-inch intake run. The unit can deliver water at a rate of 6.6 gallons per minute. Installers can connect multiple units to meet the needs of high-demand applications. The product uses either natural gas or liquid propane. Energy factor: 0.82. 334.260.1500. www.rheemtankless.com
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    Noritz. The Energy Star–rated N-0841MC tankless water heater yields 93% energy efficiency versus 60% of a typical tank water heater due to its Hybrid Super Heat Exchanger—a stainless and copper heat exchanger fused into one. The unit, which uses gas or propane, delivers up to 11.1 gallons per minute at a 35-degree temperature rise and 8.4 gallons per minute at a 45-degree temperature rise. Energy factor: 0.94. 877.986.6748. www.noritz.com
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    Rinnai. The R75Lsi delivers continuous hot water on demand up to 7.5 gallons per minute. The unit features a redesigned commercial-grade heat exchanger, an integrated condensate collector, an integrated digital temperature controller, and direct electronic ignition with no pilot light. The combustion unit is sealed, so it doesn’t use interior combustion air. Two units can be connected together without a control board. The whole-house unit measures 10 inches by 14 inches by 26 inches and weighs 46 pounds. The temperature can range from 98 to 140 degrees. Energy factor: 0.82. 678.829.1700. www.foreverhotwater.com
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    Eemax. The Series Four large-capacity electric tankless water heater is rated at 99% efficient. The whole-house unit features microprocessing temperature control. The flow activates each of the EX380T2T2’s heating elements in stages based on hot water demand. Thermostatic control delivers unlimited hot water at precise outlet temperature. Energy factor: 0.99. 800.543.6163. www.eemax.com
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    Bosch. The Bosch AquaStar 2700ES gas tankless water heater enables users to operate two to three hot water applications simultaneously. The unit delivers more than 7 gallons per minute. The product’s built-in power vent enables horizontal or vertical vent termination, and the unit offers direct, room-sealed electric combustion. The unit can plug into a 120V electrical outlet and uses natural gas or liquid propane. Energy factor: 0.83. 866.642.3199. www.boschhotwater.com

It’s no wonder tankless water heaters are becoming a staple of green building. Unlike tank-type water heaters that keep gallons of water at usable temperatures 24/7, tankless heaters provide hot water on demand, saving energy and money. In fact, the Department of Energy estimates that tankless water heaters can be 24% to 34% more efficient than tank units. According to Jack Banker, manager of tankless sales for Rheem, homeowners can save about 20% to 25% on their heating bills.

This technology isn’t new—it’s been in use in Europe, South America, and Asia for decades—but the units have only recently begun to gain traction in the United States as Americans look to cut energy costs. Technology is catching up with demand, too, as vendors are responding with whole-house tankless systems that offer capabilities beyond the capacity of early point-of-use units.

Efficient Options

The basic operation of tankless water heaters is fairly straightforward: When someone opens the hot side of a fixture, water flows into the tankless unit and past a sensor that triggers the heater to bring the water to a pre-set temperature for delivery to the fixture. The quick recovery rates on tankless water heaters allow them to operate on demand, and as long as that fixture is asking for hot water, the tankless unit will continue to heat and deliver it.

Not long ago, availability of tankless units was limited to small-capacity point-of-use systems, which would only provide enough hot water for the location where it was installed, such as a for a bathroom or kitchen sink. Now the majority of manufacturers offer whole-house systems, which can provide enough hot water for large homes with multiple bathrooms. As a result, the tankless water heater industry has grown on average about 25% per year since 1999, says Mat Katz, retail marketing manager for Bosch.

Over the years, vendors of tankless water heater units have improved their products’ performance by merging gas condensing and tankless technology, adding direct-vent technology, and integrating temperature and carbon dioxide sensors. In addition, the units have gotten more compact and more efficient.

The efficiency of tankless water heaters depends on a variety of factors, including the design and the fuel source. Gas units are about 80% to 85% efficient because residue heat is lost through the vent pipe, while electric units are nearly 100% efficient because they convert almost all the electrical energy they consume into heat. However, some homeowners prefer gas tankless water heaters because they are said to heat water more quickly. (A common complaint of tankless technology is that users must wait a few seconds for the ambient-temperature water to be expelled, the temperature to rise to the set point, and the hot water to flow through the sensor. Some vendors are circumventing this problem by allowing their systems to be installed with a circulating pump.)

Whether the best option is to go with a gas or an electric tankless water heater also depends on fuel prices and availability of natural gas in a particular area. The desired location of the tankless water heater plays a role as well. Electric tankless water heaters can be installed closer to the point of use, even for whole-house models, which can reduce the wait time for hot water; a gas unit must be installed where it can be connected to a gas line and vented outdoors. Some of these gas units offer direct-vent technology, which pulls combustion air from outside the home and discharges it through an outside vent. As a result, the tankless water heater unit isn’t discharging conditioned air from inside a home to the outdoors.