By Forrest Linebarger

Hot-water heaters are not sexy. They are primitive, hulking creatures. They heat 40-75 gallons of water 24 hours a day, seven days a week. We use them briefly in the morning or evening to take showers or wash our clothes - the rest of the time they heat water that nobody is using.

Water heaters’ inefficiency is evident in the numbers: Water heaters make up 14 percent to 25 percent of a household energy bill. When they are located in the house, they also heat the house all day long. In the summer, we pay to heat our water, then we pay to cool the house.

But there is a revolution afoot in water heating. On-demand or “tankless” water heaters have taken the market by storm. They are, well, a little sexy. They work by heating only water when you turn on the hot-water faucet.

They heat water rapidly as it passes though a highly efficient burner. They never run out of hot water. That’s right - invite the whole extended family to stay at Christmas and no one will get a cold shower.

When they first came to the U.S. market, they were underpowered by American standards. They had been used for years in Europe, but Europeans apparently liked wimpy showers. Now they have enough capacity to run two or more showers simultaneously, while saving 50 percent on energy costs.

They were also expensive, but prices have dropped so low that you can now buy a quality tankless water heater for $500-$700.

Tankless water heaters they open up floor space. The units are about the size of a computer box. They can hang on an interior or exterior wall or be placed in the attic.

Tankless water heaters’ flexibility in location means the unit can be closer to bathrooms, reducing the time to flush cold water down the drain. Traditional tank heaters, are significant causes of household fires. On-demand water systems, do not typically have pilot lights, and are usually located above flammables.

Tank heaters might last five to 15 years, whereas most tankless units have a lifespan of 15 to 20 years.

Tankless water heaters heat water rapidly, so they may require upgrading the size of the flue pipe. It is a small price to pay for such a sexy appliance.

Forrest Linebarger is CEO and chief designer at VOX Design Group Inc. and a Los Altos native. For more information, call 694-6200, ext. 511, or e-mail Forrest@VoxDesignGroup.com.