There were 201,000 search queries on "tankless water heater" performed on Google in the United States in August. Not to put too fine a point on it, but tankless water heaters are hot. Brad Pitt was quoted last year as saying he was buying one for his father for Christmas. Now that's really hot.

About the size of a medicine cabinet, tankless water heaters can easily be wall-mounted indoors, or depending on the climate, there is even a recessed outdoor installation option. Some models are available with digital wall-mounted controls and even waterproof remote controls that make it easy for users to adjust the temperature as often as they wish for convenience as well as safety. If you're designing luxury bathrooms, it's good to know the basics about tankless water heaters, because you're likely to get a lot of questions. Following are some that are most frequently asked and their responses:

Q: Will a tankless water heater save on my clients' energy bills? Is it expensive to install?
A: Tank and tankless water heaters do their jobs differently. One of the most prized benefits of tankless heaters is that users are purposely matching the use of energy to the use of hot water. It's pretty much pay as they go. Average annual operating costs for a tankless unit are about $165 to $170, or roughly half the annual operating cost of tank heaters.

Your clients should know up front that installation costs vary. In new construction, the cost of a tankless install is about the same as a conventional tank install. Replacing a tank water heater in an existing home with an indoor tankless hot water heater takes a few extra steps. Because tankless water heaters house more powerful burners than their conventional tank counterparts, they require larger gas lines. For the same reason, tankless water heaters that are installed indoors also require larger-diameter venting to the outside, either vertically through the roof or horizontally through the walls. Installation complexity can be reduced by installing the tankless water heaters outdoors or by venting indoor tankless heaters in as short a distance as possible. Your contractor will evaluate all of these issues to determine the best installation location. As a rule of thumb, installation can range in cost from $1,500 to $3,000.

Q: Will a tankless water heater provide all the hot water my clients need?
A: As long as you specify the right size of tankless water heater for your client's peak times of hot water usage, they should be happy with the performance. To give your plumber the information he needs to do a proper sizing job, ask your clients the following usage questions, provided courtesy of www.smarterhotwater.com:

• How many people are showering and when? Is there a "shower rush hour" in the morning or at night?

• Is there a deep soaking tub or whirlpool involved? What is its fill capacity in gallons? And how do they use their tub; for example, do they take a long shower first and then get into a full tub?

• When are major appliances in use? Are the dishwasher and washing machine needed at the same time family members are bathing? Most Americans are accustomed to staggering hot water use, so it is atypical to find a home where multiple hot water appliances are needed at the same time.

• How much hot water is needed to deliver the experience clients want in their bathroom remodel? How many showerheads and body sprays have been installed and what is their flow rate in gallons per minute (gpm)?

Q: Will a tankless water heater bring hot water to my clients' showers faster?
A: Regardless of whether it is a tank, tankless or solar-type water heater, delays in hot water delivery have to do with how far the water heater is located from the hot water outlet, not the type of water heater. Tankless water heaters often do solve this issue because of their smaller size, which enables them to be located closer to the point of use.

Another solution is a point-of-use water heater. Point-of-use heaters are actually smaller tank units that are located near the hot-water outlet, such as under a sink. They are often used to augment larger tank-type water heaters that are located far from the point of use. A recirculating system is another option to discuss with your plumber partner.

Q: What is the payoff for kitchen and bath designers who learn to stop worrying and love water heaters?
A: Ask Marcio Decker, winner of the Smartest Hot Water Use Award in the National Kitchen & Bath Association's 2008 Design Competition. "We are moving more and more into what is hidden behind the walls," he explained. "Now, more than ever, there is the need to create environments that are eco-friendly. Water use in the bath, and water heating specifically, are very important. We designers should collaborate with other professionals to make sure that energy efficiency is part of every project."


—Nora DePalma is partner and principal of Building Profits, Inc., a marketing communications firm specializing in building products.