Several manufacturers of tankless heaters had exhibits at the show.
"It usually takes a technology 15 years to go from the drawing board into universal use," said Michael Luzier, the new president of the National Association of Home Builders Research Center in Upper Marlboro, Md., which has tested tankless heaters for PATH for the last few years.
"In the case of tankless heaters, the testing that we did has helped accelerate that process," Luzier said. "The goal is to get such technology to the marketplace in a shorter time."
Tiffani Thompson, specialty-product sales manager at Rheem Water Heaters, said: "The whole concept is really taking off here in the U.S., and this market is expected to increase 15 percent this year."
Rheem, the venerable manufacturer of HVAC systems, introduced its RTG42 PV model at the show. This heater, which produces 4.2 gallons of hot water per minute, is an indoor model that runs on natural gas or propane and is designed for apartments, she said.
Tankless units heat and deliver water on demand. Cold water is circulated through a series of burners or electric coils that heat the water as it passes through. There is no storage tank.
Tankless units cost more than storage heaters, but since you are not heating a big tank of water 24 hours a day, they cost less to operate.
Not surprisingly, having abundant hot water is important to homeowners. A nationwide survey of 800 homeowners by Public Opinion Strategies of Washington found that 90 percent of respondents considered hot water the one convenience they could not do without. Fifty-two percent said they could live without a TV.
"Homeowners love having the latest and greatest technology, but realize it is the basic home functions that get them through their daily lives. So [they] are almost always on the lookout for anything that makes getting to and using those life essentials more convenient," said Ervin Cash, a vice president of Rinnai America Corp., whose Continuum tankless heater was installed in the Ultimate Family Home show house at January's builders show.
Heating water accounts for 20 percent or more of a typical household's annual energy expenditures, according to the U.S. Department of Energy. The yearly operating costs for conventional storage-tank water heaters average $200 for gas units or $450 for electric ones.
Storage-tank water heaters raise the water temperature to the setting on the tank, usually between 120 and 140 degrees, and maintain it there.
Even if no hot water is drawn from the tank (and cold water enters the tank), the heater will operate periodically to maintain the temperature.
This is the result of what are called "standby losses": the heat conducted and radiated from the walls of the tank, and in gas-fired water heaters through the flue pipe. Standby losses represent 10 percent to 20 percent of a household's annual water-heating costs.
Although tankless heaters have been popular in Europe and Japan for a long time - indeed, several manufacturers of units available in this country are Japanese - concern over having enough hot water has kept them on the back burner, so to speak.
Even the largest whole-house tankless gas models cannot supply enough hot water for simultaneous multiple uses, such as showers and laundry, according to the Energy Department. Large users of hot water, such as clothes washers and dishwashers, need to be operated separately.
On the other hand, separate demand, or point-of-use, electric tankless heaters can be installed underneath sinks or in closets near the shower, sink or washer to handle individual hot-water loads.
Point-of-use heaters for sinks and showers have long been popular with owners of vacation houses that have electric service. Unlike tankless gas heaters, the electric ones do not require outside venting.
They also are much smaller than tank heaters. Although sizes vary, the average is about 24 inches high, 18 inches wide, and 9 inches deep - taking up a little more than two cubic feet.
Tankless units are wall-mounted, and can be placed indoors or outdoors.
The Rinnai Continuum tankless units used in the Ultimate Family Home at the builders show actually took up 16 square feet less than the tank heater necessary to provide the 5,300-square-foot house with hot water.
The largest Rinnai residential units can supply 8.5 gallons per minute.
A compact model manufactured by Takagi Industrial Co. USA provides 240 gallons of hot water per hour, and takes up only 2.2 cubic feet of space.
Thompson said the 7.4-gallon-per-minute model that Rheem Manufacturing Co. makes is more a whole-house tankless. "The heater needs to be properly sized for the house," she said. "If you don't, you'll run out of water in the middle of a shower if someone decides to wash dishes in the kitchen sink."
Electric tankless models are not designed for whole-house operation.
When the National Association of Home Builders Research Center installed point-of-use tankless units in one of its demonstration houses, it had to increase the house's electrical service from 200 amps to 300.
The Rinnai, Rheem and larger Takagi units aside, residential gas-fired models now on the market typically supply only 5 gallons of water per minute heated by 90 degrees. Electrically heated models provide even less hot water: 2 gallons a minute heated by 70 degrees.
By providing hot water immediately where it is used, tankless heaters waste less water: People do not need to let the water run as they wait for warmer water to reach a remote faucet.
Equipment life may be longer than with tank-type heaters because tankless models are less subject to corrosion. The expected life of tankless water heaters is 20 years, compared with 10 to 15 years for tank-type heaters.
Tankless heaters range in price from $200 for a small under-sink unit to $1,000 for a gas-fired unit that delivers 5 gallons per minute. Those numbers do not include installation, which can add $150 to $300 to the price.
Typically, the more hot water a unit produces, the higher the cost. Electric tankless heaters typically cost more to operate than gas units.
Some drawbacks to demand water heating are:
Unless your demand system has a feature called modulating temperature control, it may not heat water to a constant temperature at different flow rates. That means that water temperatures can fluctuate uncomfortably - particularly if the pressure varies wildly in your water system.
Electric units will draw more instantaneous power than tank-type water heaters. If electric rates include a demand charge, operation may be expensive.
Electric units also require a relatively high power draw because water must be heated quickly to the desired temperature. Make sure your wiring is up to the demand.
Tankless gas water heaters require a direct vent or conventional flue. If a gas-powered unit has a pilot light, it can waste a lot of energy, and, depending on design and the cost of gas, pilot lights can cost $12 to $20 per year to operate. (The Rheem and the Takagi gas-fired units at the builders show came without pilot lights.)
Contact real estate writer Alan J. Heavens at 215-854-2472 or email@example.com.