Assess Efficiency
The next number to look at is the energy factor (EF), a number that represents the percentage of energy that is turned into hot water by that specific model. The higher the number, the more efficient the unit and the less it will cost to operate. (An EF of 1 would indicate that 100 percent of the energy a heater uses is converted into hot water—a physical impossibility, alas.) While a high EF is good, you have to factor in the cost of the energy the heater uses to get a true picture of how much it costs to operate. In most areas, for example, an electric heater with an EF of 0.8 will cost more to run than a similar-size gas model with an EF of 0.6, due to the higher price of electricity compared with gas. In most cases, water heaters with high EFs cost more to buy, but don't overlook the potential long-term savings in fuel costs. Here's an easy formula to calculate the payback period when comparing heaters that have the same FHR rating but different prices: Divide the difference between the prices of the two models by the difference between their estimated annual operating costs (printed on the Energy Guide labels). The result is the number of years it will take the energy savings to offset the higher purchase price. Look for a payback within 10 years, the expected life span of an average heater. Of course, if energy prices go up during that time, the payback period will be shorter.
Keep in mind that the estimated annual operating cost is just an approximation. To more accurately predict performance and payback time, plug each model's EF and your actual energy cost into the online worksheets provided by GAMA (www.gamanet.org/consumer/consumer.htm).
Performance Features
After determining a heater's size and efficiency rating, consider these other important factors that increase longevity and reduce operating costs.
Tank material: The typical tank is steel lined with "glass" (actually porcelain enamel). It contains anodes—magnesium or aluminum rods—suspended in the tank to fight internal corrosion, the number-one reason water heaters fail early (see "Rust Busters," December 1999, page 76). Stainless steel tanks don't rust (and therefore don't need anodes), but they're more expensive than glass-lined tanks. Their higher cost may be worth it in areas where the water is highly corrosive (acidic) or reactive (full of minerals that encrust the tank walls, slowing heat transfer).
Insulation: Whether foam or fiberglass, the insulation surrounding a gas- or oil-fired tank should be R-16 or higher, and R-22 or more for electric. Insulation reduces standby losses—heat that escapes while the unit is idle. Wrapping your tank in a fiberglass blanket won't make up for insufficient insulation built into the tank.
Heat traps: These built-in devices—either valves or flexible connectors bent into an inverted U—put a stop to "thermosyphoning," the tendency for hot water to rise up the supply pipe. If your water heater doesn't have one built in, a heat trap can be added during installation (or retrofitted to existing heaters).
Making Your Selection
Factor in warranties and the manufacturer's reputation before making your purchase. There's no single source to turn to for this information; talking to a few reputable plumbers and plumbing-supply stores should help you narrow the choices. Also, you may be able to take advantage of rebates or incentives offered by local utilities and municipalities to encourage the purchase of energy-efficient models. (Check www.dsireusa.org for state-by-state listings.) Finally, make sure the heater you've chosen will fit in the available space and still leave enough room for servicing.
Once you're ready to buy, your plumber should be able to order the model you want. Or, you may be able to buy directly from a local home center. In either case, professional installation will take about one to three hours; be sure it includes the cost to remove and dispose of the old heater.
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