By Mary Ellen Polson
Panels for solar water heaters usually have a smaller footprint than those for overall heating. (Courtesy: SolarSource.net)
Conventional water heaters consume as much as 20 percent of your home’s energy budget. New federal energy mandates now require greater efficiency for nearly all residential heaters, regardless of fuel. While most tankless systems already exceed the new standards, others are catching up, especially condensing and hybrid water heaters.
The Accelera from Stiebel-Eltron heats water by drawing on air in a basement or garage.
The size of the house, the number of people in the household, the type of power available (gas or electric, for example), and climate considerations all have a bearing on heating options for hot water. That said, the most important factor in choosing a new heater is the first-hour rating (FHR) for storage-tank water heaters and the gallons-per-minute rating (GPM) for tankless water heaters.
In essence, these ratings tell you how quickly you’ll run out of hot water when multiple users are draining the taps.
A professional can help you estimate what FHR or GPM your household needs. For a storage unit, you’ll also need to know the recovery rate—how fast the heater can replenish water as it’s drawn from the tank. In most cases, this will depend on the burner size (in BTUs) and heat-transfer efficiency.
Another important consideration is the energy factor (EF), a measure of the amount of hot water produced per unit of fuel consumed over a typical day. While a high EF is desirable, it doesn’t necessarily mean that the option with the highest EF will be most cost efficient. That will depend on your climate and how and when you typically use hot water. For more information on estimating costs and efficiency, see energy.gov/energysaver/selecting-new-water-heater.
The Westinghouse stainless steel electric hot water heater has an energy factor (EF) of .95.
STORAGE TANK The most familiar household water heater is a 50-gallon insulated tank that heats and stores water. (Larger and smaller size tanks are also available.) Newer models offer better tank insulation and higher ER ratings.
Pros They cost only a few hundred dollars each, and can be installed by a plumber in just a couple of hours. They’re most efficient when powered by natural or LP gas.
Cons Keeping water in the tank hot on standby means higher overall energy consumption and costs. It’s still possible to deplete all the hot water at one time, too, if too many people are drawing it down at the same time.
HEAT PUMP/HYBRID Heat pump and hybrid water heaters pull heat out of warm air in an uncooled space like a garage or attic to heat hot water.
Pros Ideal in temperate to warm climates, hybrids use about 60 percent less energy than standard electric water heaters. They’re slightly more expensive than standard tank heaters.
Cons Hybrids require up to 1,000 cubic feet of space to work properly.
Heatworks’ Model 1 is an electric, digital water heater that can be used to heat a small house.
TANKLESS/ON-DEMAND Rather than storing water, a tankless water heater fires up the heating unit when the demand is made.
Pros Tankless units are usually smaller and more compact that storage tank heaters. They are significantly more fuel efficient, especially when powered by gas.
Cons Tankless water heaters usually require significantly higher set-up costs (thousands of dollars instead of hundreds) due to requirements for larger gas lines and the installation of flues.
Rheem’s 48-gallon high efficiency, direct vent condensing water heater can supply more than 90 gallons of hot water in the first hour.
CONDENSING
A condensing heater captures hot combustion gases that are normally vented out of a standard unit and routes them to a series of sealed coils. Water flows around the coils, collecting most of the heat before the cooled gases are finally exhausted.
Pros Condensing water heaters can be more energy efficient than many tankless water heaters, and cheaper to install.
Cons Condensing units are more expensive than conventional heaters, and can only be used in homes with natural or LP gas.
SOLAR
Solar panel cells mounted on the roof absorb heat from the sun and deliver it to a closed-loop system that serves the hot-water tank.
Pros Solar water heaters work best in sunny climates, where they can reduce water heating costs to nil on days with abundant sunshine. Installation may qualify for up to a 30 percent tax credit through state and federal programs.
Cons On cloudy days, a backup system is required. Placing solar panels on a historic building can be problematic. Despite tax incentives, it can still take 10 to 30 years to recover installation costs.
The Tronic 3000T spot water heater from Bosch costs less than $200.
POINT OF USE
Spot water heaters work on the same principle as tankless heaters but deliver water to only one point: the sink in a kitchen or bathroom, for example.
Pros A point-of-use heater can reduce water waste and dramatically shorten waits for hot water at frequently used locations.
Cons Can be noisy.
Resources
Bosch bosch-climate.us
Heatworks/ISI Technologies myheatworks.com
Rheem rheem.com
Rinnai rinnai.us
Solar Source solarsource.net
Stiebel Eltron steibel-eltron-usa.com
Westinghouse westinghousewaterheating.com
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