By Rob Fanjoy
Homeowners are beginning to learn that the lowest-priced water heater may be the most expensive to operate and maintain over its lifetime. By the same token, an oversized unit carries a higher purchase price and increased energy costs.
The best way to cut down on costs is to choose the right-sized water heater — and that's a very easy task. Properly sizing a water heater first involves estimating the appropriate First Hour Rating (FHR) based on estimated hot-water use. FHR describes the amount of hot water (in gallons) a water heater can provide in the first hour, starting with a full tank of hot water. The FHR depends on the tank capacity, the source of heat (burner or element) and the size of the burner or element.
The FHR rating appears on every EnergyGuide label in the top left corner (except on heat-pump water heaters). To get the proper size, look for a water heater with an FHR that matches the home's anticipated peak water demand within one or two gallons. There are several worksheets available to help you figure peak demand; check the
Gas Appliance Manufacturers Association’s website or chapter 48 of the 1999 ASHRAE Handbook of HVAC Applications.
Besides the FHR rating, consider these other factors when choosing a tank-style water heater:
- The Energy Factor (EF), also shown on the EnergyGuide label, shows the unit's energy efficiency based on how much hot water is consumed in an average day. The higher the EF, the more efficient the unit.
- Look for models with a thermal resistance (R-value) of R-12 to R-25.
- Gas and oil water heaters also have venting-related losses. Look for units that are either fan-assisted or have atmospheric sealed-combustion chambers to reduce these losses.
If you're looking for an even more energy-efficient way to heat water, consider installing tankless water heaters, which use a heat exchanger or coil installed in a furnace or boiler to heat water directly. According to the U.S. Department of Energy, water heating accounts for about 14 percent of the average U.S. household energy budget. A lot of that money goes down the drain in the form of standby losses -- energy lost from warm water sitting unused in a tank. Tankless water heaters can save homeowners a lot of that money, since they provide hot water at a preset temperature only when needed, eliminating standby loss.
While tankless water heaters may cost more at first, they pay for themselves very quickly.
Tankless water heaters range in price from $200 for a small under-sink unit up to $1,200 for a gas-fired unit that can deliver five gallons of hot water per minute. That is considerably more hot water than typical tank systems; however, many of the new high-efficiency tank units cost nearly as much as the high-end tankless ones.
Installation costs for a tankless water heater can run from two to four times higher than tank types, too. Installation is easiest in new construction; in retrofit applications, re-sizing of gas supply lines or extra wiring may be needed.
According to the NAHB Research Center, electric tankless water heaters generally cost 10 percent to 20 percent less to operate per year than conventional tank-type heaters, while gas tankless units cost 20 percent to 40 percent less per year to operate. The expected life of tankless units is also greater: 20 years as opposed to 10 to 15 years for tank-type units.
Rob Fanjoy is the former editor of Smart Homeowner magazine. He is in the process of remodeling his own Michigan home for greater energy efficiency.
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