Water heater buying guide

Most water heaters are sold on the basis of how many gallons they hold. For example, two to four people might use 80 to 85 gallons per day--enough for about three showers, one laundry load, running the dishwasher once, and turning on the faucet nine times. But the first-hour rating (FHR) for storage-tank water heaters and the gallons-per-minute rating (GPM) on tankless water heaters are more important, because they tell you how much hot water the heater can deliver during a set period. A pro can calculate how much you'll need.

Most of these are essentially steel cylinders fed by a cold-water inlet pipe (the dip tube) that protrudes into the tank (this line includes the shutoff valve). Water is heated in the tank, and hot water exits through a hot-water pipe atop the tank. Another pipe that emerges from the tank includes the temperature and pressure-relief valve, which opens if either exceeds a preset level. You'll also find a drain valve near the tank bottom and a control unit outside for setting temperatures and, on gas models, controlling the pilot-light valve.

Gas is the fuel of choice if you already have natural-gas service or can run a gas line to your home economically. Gas models cost more than electrics. But on the basis of national-average fuel costs, a gas water heater will cost you about half as much to run as a comparable electric model. Thus, a gas heater might amortize the up-front difference in cost in as little as a year. While you'll also find oil-fired storage heaters, they're relatively expensive, because they include the tank and an oil burner. That's why homes with oil heat typically use an electric water heater.

Tankless models (a.k.a. instantaneous water heaters) are suitcase-sized units that heat water only when needed by using an electric coil (typically for low demand) or natural gas (for high demand) to heat water passing through a heat exchanger inside. They eliminate the risk of tank failure and the energy lost by constantly reheating water, though their heat exchanger can clog or fail. What's more, they're expensive to buy and install, and include limitations on hot-water flow rates, a possible issue in large households. And cooler incoming water in winter typically means your hot water may not be as hot as you like.

These have a conventional electric storage heater paired with a heat pump that extracts heat from the surrounding air and uses it to help heat the water. Models we tested used about 60 percent less energy than standard electric heaters, which account for about half of all water heaters sold. And while hybrids cost more than electric-only models, installation is similar and payback time is short.

But hybrids also have their downsides. Because the heat pump is usually on top, they need as much as 7 feet from floor to ceiling. You'll also need up to 1,000 cubic feet of uncooled space to capture enough heat from the air, along with a condensate pump (about $150) if there's no drain nearby. Hybrid heaters are noisier than conventional storage-tank heaters, exhaust cool air, and can rob some heated air in winter.

All solar heaters supplement an electric heater in basically the same way: A roof-mounted collector absorbs the sun's heat and transfers it to an antifreeze-like fluid in a closed-loop system that runs to the water tank. The collector is typically a flat panel or an array of glass cylinders called evacuated tubes. The best delivered stellar savings in summer, making them an attractive option for warm, sunny areas. But savings suffered on cold and cloudy days. And even with federal and local rebates, the thousands you'll typically spend to buy and install one can mean you'll wait anywhere from 10 to 30 years before their savings pay for their costs.

The water-heater market is split about 50-50 between electric and natural gas. Oil-fired heaters account for only a small percentage of sales, most likely because of their relatively high price and the small market for oil-burning equipment.

Coverage for most heaters typically runs 3 to 12 years. While you'll usually pay a bit more for longer-warranty models, we've found that they tend to have larger elements or burners that can speed up water heating, essentially increasing the hot water available, along with thicker insulation for less heat loss. We suggest choosing models with the longest warranty available.

Some brands--notably, Kenmore, State Industries, and Rheem--advertise features that are supposed to reduce buildup of mineral scale at the bottom of the tank by swirling the water. While scale can shorten the life of the heating element inside an electric water heater, you don‘t need to invest in fancy features to get a long-lived model. Simply look for a heater with a 12-year warranty, which typically includes a longer or thicker element.

These valves are situated near the base of the unit to accept a garden hose for draining the heater. Look for brass drain valves, which tend to be more durable than plastic.

A glass-lined tank is another feature designed to reduce corrosion. During manufacturing, a coating is applied to the inside of the steel tank and heated to form a protective, porcelain glass-like layer.

Found mostly on hybrid and solar heaters, these help you monitor levels and customize operation. Some electric/heat-pump hybrid models let you digitally set a "vacation mode" that uses just the heat pump for added efficiency when you're away. Displays on solar heaters often show tank and collector temperatures, along with pressure readings and other helpful data.

A top-mounted heat pump on hybrid water heaters typically makes them taller than conventional models. Tougher federal standards have also spurred companies to beef up the insulation on regular storage-tank heaters, adding about four inches of width over earlier versions--a potential problem in tight spots. (Hint: Adding insulation to hot-water pipes that exit the heater can add efficiency to any water heater.)

Residential tank-type gas heaters typically include flammable-vapor ignition resistance (FVIR) to prevent flashback fires when vapors from a flammable liquid such as gasoline contact the burner or pilot light. Also be sure your home has carbon-monoxide alarms if you have a fuel-fired water heater or any fuel-burning device, including a fireplace. And because heaters are generally vented through the same chimney as a furnace or boiler, if you change venting for one appliance, you might need to change it for the other. Considering a tankless water heater? If you run a vent pipe to the outside of your house, you'll need to use Category 3 stainless-steel venting to resist corrosion from any condensation that forms in the pipe.

General Electric makes gas and electric water heaters. GE tank water heaters are available in multiple sizes, with energy efficiency claims that vary by size and multiple levels of warranty coverage. The company’s tank water heaters are available exclusively at Home Depot. General Electric recently introduced a line of tankless water heaters.

Kenmore makes gas and electric water heaters. Kenmore water heaters are available in multiple sizes, Power Miser, and Hydrosense electronic-temperature-control configurations. Kenmore water heaters are available at Sears.

Rheem manufactures and markets gas and electric water heaters. Rheem makes residential water heaters in tank, tankless, and point-of-use configurations and units that work with solar-water-heater systems. Rheem water heaters are available in multiple sizes and warranties, with energy efficiency claims that vary by size. Rheem tankless water heaters are available at Home Depot. Its tank water heaters are available online and through a network of dealers.

Whirlpool manufactures and markets gas and electric water heaters. Whirlpool tank water heaters are available in multiple sizes, and standard and power vent configurations. Whirlpool water heaters are available at Lowe’s.