Opinions on tankless water heaters run hot and cold

Compared with other "green" purchases, the stakes get a little higher when you buy a tankless water heater. We all rely on hot water. We want it to be there when we need it.

Only a small number of adventurous homeowners have installed tankless water heaters. Some folks love them. Unfortunately, others who have purchased these have had nothing but trouble and cold showers. The environmental advantages make tankless water heaters worth considering. But before taking the plunge, do your homework. And follow these tips to make sure a tankless decision doesn't end up thankless.

Lots to like

Standard water heaters have inherent inefficiencies. Even when you're not using hot water, they require energy to keep water hot and ready to go.

In contrast, a tankless (or "on demand") system heats cold water instantly as it flows through heating elements or a heat exchanger. These systems have been widely used in Europe and Japan for years.

A tankless unit can reduce energy usage for water heating by 10 to 20 percent, according to ToolBase Services, a federally funded resource for information on home construction technology.

They can also save money over the long run, says ToolBase. Electric tankless water heaters generally cost 10 to 20 percent less to operate than tank-type water heaters. Savings with a gas tankless water heater should be even higher, from 20 to 40 percent.

And tankless systems have an expected life of 20 years, compared with 10 to 15 years for tank water heaters. Because a tankless unit may cost two to four times as much to install as a regular water heater, it may take several years to realize those savings.

In addition, a tankless water heater will provide unlimited hot water when sized correctly. This is great if a family wants to take five hot showers in a row. But you have to be careful this feature doesn't result in longer showers, wasting water.

Tankless water heaters also take up much less space than a regular water heater. A typical tankless unit hangs on the wall and measures about 24 by 18 by 9 inches.

Don't get burned

The most commonly reported problem with these units is that they cannot provide hot water consistently, for a multitude of reasons.

I know two people who installed tankless water heaters with great expectations, but have had cold water splashed on their hopes. One friend yanked his out. It now sits forlorn on the floor of his garage.

Since several of the major brands seem prone to problems, it's important that you talk to people who have used the contractor and brand you're considering.

Also check out Web sites that compile product reviews from the public. For example, if you do an online search for "Bosch tankless water heater Epinions," you can find about 30 reviews of a Bosch model on the Epinions Web site. Greenerbuilding.org has more than 50 reviews each for the Rinnai and Titan brands, which you can find by searching "tankless" on that site.

Even though some Seattle-area residents have reported product failures on these sites, it does appear that tankless water heaters generally perform better in mild regions like ours than in colder climates.

Tankless checklist

Before you buy, get three or more references for the contractor and system.

And ask these questions:

• How much experience does the contractor have installing these systems?

• In addition to the purchase price for the unit, will you face major additional costs, such as for required stainless-steel vent pipes?

• How long is the warranty, and what exactly is covered? How much will repair calls cost?

Other tips

• Thoroughly assess your hot-water usage to determine the proper size unit you need.

• For a gas system, avoid those with pilot lights; an electronic ignition uses less energy.

• If you buy a tankless water heater before Dec. 31, 2007, you can claim a federal energy-efficiency income-tax credit of $300 (most brands qualify).

• A hot-water recirculation pump is a separate type of device that works with a standard water heater to make hot water more rapidly available. These may provide minor energy and water savings, but not nearly as much as a tankless system.

Tankless water heaters may be a few years away from hitting their stride. But they still hold immense promise, and it would be a mistake to dismiss them entirely.

Tom Watson, project manager for King County's Recycling and Environmental Services, writes the EcoConsumer column for the digs section in Saturday's Times. Reach him at tom.watson@metrokc.gov, 206-296-4481 or www.KCecoconsumer.com.