GE

Available in indoor or outdoor models, these tankless gas water heaters measure 23 inches high, 14 inches wide, and 10 inches deep, making them ideal for small spaces, such as attics and closets. Users can choose from two flow rates: a natural-gas 7.5-gpm model or a 9.4-gpm unit available in natural gas or LP gas. By heating water only when needed, the tankless units maintain efficiency ratings of .82, compared with .53 to .62 for standard water heaters, and can save homeowners up to 25 percent on water-heating costs annually, the manufacturer says. 800-626-2000. www.ge.com.