Types of water heaters

Fueled by electricity, propane or natural gas, storage tank-type water heaters are the most common type used in the United States today. They are also the least expensive to buy and install. Tank water heaters are less energy efficient because they continually use energy to keep the storage tank full of hot water -- whether you are currently using that water or not. The advantage is almost-instant available hot water, no matter how many appliances are running or chores are being accomplished. The downsides are that you waste energy keeping 40 to 60 gallons of water hot all the time as the unit cycles on and off all day -- and if you run too many appliances at once or take too many showers in a row, you'll run out of hot water in the tank. This type of water heater has a life expectancy of 10 to 12 years.

Tankless water heaters are also called 'on-demand' water heaters. Long popular in Europe and Asia, tankless water heaters are compact heating units that fire up only when you need them, heating only the water you use, then shutting down as soon as the faucet is turned off. They may be used as a home's sole source of water heat, or to augment traditional or solar water heating systems. Smaller point-of-use tankless heaters can provide hot water to kitchens, washing machines or remote bathrooms.

Advantages to tankless water heaters include greater energy efficiency of 10 to 20 percent over tank water heaters. Because they do not store a reservoir of hot water, there are no standby losses. Tankless water heaters can supply limitless amounts of hot water. Their housing is more compact, with a longer life expectancy of about 20 years. Downsides include the high cost -- twice or more of what you'd pay for a traditional tank-style water heater. Editors at Consumer Reports say you're unlikely to make up the extra expense in energy savings. Installation can be tricky, and gas units may require wider-than-usual vents and larger gas pipes running to the meter, adding another $500 to $1,000 to the initial installation cost. Pipe and vent issues also make installing a tankless water heater in an older home more difficult, and hot water may take longer to reach remote rooms.

Solar water heaters are the third major type of water heater. The big advantages here are the reduction of greenhouse gases and the energy savings. A solar water heater can reduce your hot water heating bill by 60 to 95 percent, potentially saving hundreds of dollars a year. However, upfront and installation costs can be high, anywhere from $1,500 to $5,000, although you'll likely quality for a federal tax credit. But solar water heaters may not completely replace electric or gas water-heating systems. These conventional systems are still necessary as supplements, principally because the sun might not shine in your location for several days at a time. Many solar water-heating systems are designed to preheat water that goes to a backup heater -- typically a conventional gas or electric water heater. A tankless heater will also work as a backup, as long as it is designed to accept hot-water input (not all of them are).

Best tank-type water heaters

Tank-type water heaters heat water in an insulated cylinder that ranges in size from 20 to 80 gallons of water. The majority of homes use a 40 to 60 gallon water heater. A typical tank is steel lined with glass; some higher-end models are available with stainless steel linings for those who live in areas where the water is acidic or full of minerals. Suspended in the tank are anodes -- magnesium or aluminum rods formed around a steel core wire to prevent corrosion. A six-year-warranty residential tank will have one anode, while a 12-year-warranty tank will have two, or an extra-large primary anode. Warranties are important. Editors at Consumer Reports found that there is a direct relationship between warranty length and better insulation, heat transfer and larger heating elements. Look for longer coverage, particularly if you have hard water and use water softeners, since this can speed up eventual anode corrosion.

The first advantage of a tank-type water heater is the low cost. A new residential storage water heater costs an average of $500 to $600 including installation (according to Consumer Reports). If you have an available gas line, you'll probably save money by going with a gas water heater, since gas rates are usually lower than electricity rates.

If you want a gas water heater, we found good comments for the A.O. Smith "Conservationist" series and Maytag's "Series 12," both of which are made by A.O. Smith. The A.O. Smith Conservationist water heaters (*est. $350 to $450 plus installation for a 40-gallon tank) have 2-inch thick foam insulation, an automatic sediment-cleaning system, and a push-button spark ignition. A stainless steel core anode provides additional protection for hard-water situations. This series offers a ten-year limited parts and tank warranty.

There are three models in this series. The 40-gallon tall-tank model has a first-hour rating (FHR) of 81 gallons. The FHR number is important, since it tells you how many gallons of hot water you can expect during a peak hour of usage (see below for estimating your capacity needs). The 60-gallon tall tank has an FHR of 97 gallons. Both are about 65 inches tall. A 40-gallon short tank (56 inches) is also available, but this unit has a lower FHR of 74 gallons. All have an energy efficiency factor (EF) of .63. All have a BTU input of 40,000.

Maytag Series 12 water heaters, which are also made by A.O. Smith, also have a .63 energy factor, 2-inch foam insulation, and a self-cleaning cold-water inlet to counteract sediment buildup. A Piezo igniter allows one-hand pilot lighting. Two heavy-duty anode rods protect against corrosion, and there is a 12-year tank and parts warranty. This series is available in 40-gallon (81 FHR, *est. $420) and 50-gallon (84 FHR, *est. $450) sizes with 40,000 BTU input. A 50-gallon size with 65,000 BTU has an FHR of 93 gallons, and a 75-gallon size (*est. $530) has a 75,100 BTU input with a 128-gallon FHR.

A.O. Smith also makes similar water heaters under the Kenmore, American Water Heater and State Industries brands. Kenmore water heaters have an advantage for do-it-yourselfers since they are easy to find online or at your local Sears store. Most models in the Kenmore Power Miser 12 Natural Gas Water Heater series have two anodes, two inches of foam insulation, a .63 EF, and a 12-year limited warranty. This series is available in 40-gallon (81 FHR, *est. $420), and 50-gallon (97 FHR, *est. $450) sizes with 40,000 BTU input. A 75-gallon size (114 FHR, *est. $530) is available with 55,000 BTU input (1 inch of insulation and an R8 insulation value).

Kenmore Power Miser gas water heaters are also available with a nine-year warranty as the Power Miser 9 series. These models have 1 inch of insulation rather than 2 inches, and one anode rather than two. The price difference between the 40-gallon Power Miser 9 (*est. $350) and 40-gallon Power Miser 12 (*est. $420) is about $70.

If you rely on propane fuel, propane water heaters are available, though they are a little harder to find. While A.O. Smith doesn't market propane water heaters under its own brand, it does make propane water heaters under the Kenmore brand name. Liquid-propane fueled models include the Power Miser 9 40-gallon (*est. $420), along with a series of propane water heaters with a six-year warranty, the Power Miser 6 30-gallon (*est. $250), 40-gallon (*est. $360) and 50-gallon (*est. $410).

Bradford White is judged the best water-heater brand in a poll of over 300 contractors, who rated companies based on ordering, product quality and service, among other factors. This might not be too surprising since Bradford White sells water heaters only through plumbers rather than retail outlets. Bradford White hot-water heaters offer electronic ignition systems, fully automatic thermostat controls, and jet ports that clean the tank every time there is a call for hot water. Rheem/Ruud is another brand that offers a self-cleaning system and two anode rods to fight sediment buildup, as well as 2.5 inches of foam insulation. Rheem/Ruud water heaters are available mainly through plumbers.

An electric water heater will usually have a higher operating cost due to higher rates for electricity over gas. When it comes to electric hot water heaters, Jim Dulley recommends Rheem/Ruud, with its lifetime warranty if you plan on staying in your home at least ten years. You may also want to consider Maytag's Series 12 PC Intelligent water heaters. These models allow you to program the water heater for different periods of the day, so that you can -- for example -- dial down the temperature when you are away for the day.

A.O. Smith's Conservationist series, with its longer-lasting heating elements, are available as electric water heaters. These models come in 40-, 52-, 66- and 80-gallon sizes, all with a high efficiency rating of .95. First-hour ratings range from 56 to 81 gallons, depending on the model. According to the American Council for an Energy-Efficient Economy, an energy rating of .95 is as high as you can get with an electric water heater.

Bradford White water heaters have two factory-installed heat traps and a heavy-gauge steel tank to protect against corrosion and rust. Reliance Sta-Kleen electric water heaters are self-cleaning and have two heating elements. Rheem's Marathon model has a plastic and fiberglass tank that will not rust, corrode or leak. State Industries' Premier models have jet ports for self-cleaning, 3 inches of foam insulation and a ten-year tank and parts warranty.

The only owner reviews we found of electric tank water heaters are at Epinions. Two owners of Sears Kenmore Power Miser water heaters are very positive. Kenmore offers these with a nine-year warranty as the Kenmore Power Miser 9 (30- to 55-gallon sizes, *est. $280 to $310) and with a 12-year warranty as the Power Miser 12 series (30- to 55-gallon sizes, *est. $280 to $330). Users like the self-cleaning system that aids against high mineral content along with a glass-lined tank with two rods to protect against corrosion. Both models have 2.5 inches of foam insulation. The tanks have a system that converts to fit your wiring, adapting from 2800 to 5500 watts. The whole system is contained in a steel shell.

Otherwise, we found very few reviews for tank-type water heaters. But since the Department of Energy and Consumer Reports says that similar models tend to perform within a narrow range of each other, you have the freedom to choose based mainly on size, insulation and warranty. Although any of the models covered above are good choices, we've included two Kenmore water heaters in ConsumerSearch Fast Answers mainly based on their availability online and in Sears stores.

Home Depot and Lowe's also carry water heaters, so you can compare models there as well. Lowe's carries Whirlpool water heaters, including the Flame Lock line. We found few reviews for water heaters in general, but ConsumerAffairs.com reports on over 100 complaints about the Whirlpool Flame Lock line. These come in 30-gallon (*est. $315 to $350, depending on warranty length), 40-gallon (*est. $320 to $450) and 50-gallon sizes (*est. $425 to $490). Those users report problems with a breaking thermocouple -- and since the thermocouple is a non-standard configuration, getting a replacement is difficult. The Whirlpool Flame Lock series was the only water heater for which we found consistent complaints.

Tankless water heaters

Tankless water heaters are compact heating units that fire up only when you need them, heat only the water you use, and shut down as soon as the faucet is turned off. When the hot water tap is turned on, water enters the unit and a sensor activates a heating device to raise the water temperature. Tankless units can be heated by gas (which may require a power vent and a separate gas supply) or electricity (which may require multiple circuits and a larger service size). Tankless water heaters may be used as a home's sole source of water heat, or to augment traditional or solar water heating systems. Smaller point-of-use tankless water heaters can provide hot water to individual appliances or remote bathrooms.

Although tankless water heaters save money on energy costs, they are much more expensive to buy, typically more than double that of a standard tank-style water heater. Sizing is important, and you may find that you need pipe and gas-line renovations before you can install a tankless water heater. Hot-water production is measured as gallons-per-minute (gpm). A unit that produces less than 2.5 gpm won't provide enough hot water for an average household. If you need a tankless water heater to supply an entire family with hot water, look for one that has an input of no less than 165,000 BTU.

Performance of a tankless water heater may be greatly affected by the temperature of your groundwater. If it's very cold, a tankless water heater will have a hard time producing hot water quickly. In reviews we read, owners living in milder climates seem to be happier than those in cold areas, where the incoming groundwater can be colder than the U.S. average of about 50° Fahrenheit. That's because the flow rate is greatly reduced when the incoming groundwater is very cold. Flow rates are qualified by the number of degrees you need to raise your groundwater temperature. Those living in mild climates will get a much better hot-water flow rate, while those in cold climates might only get half as much.

Despite the potential for energy savings, we found a lot of mixed reviews for tankless water heaters in general. Owners report problems with flow delay -- having to wait several minutes for hot water. Many relate 'strategies' for dealing with the delay, and say that you'll likely need to change your behavior to be happy with a tankless water heater. Since there's no constant supply of hot water, you won't want to turn a faucet on and off too much while you are doing dishes, for example, since the unit will have to keep cycling on and off and you'll get cold water again each time you turn the faucet back on. Most tankless heaters need about ¾ gallon of water before hot water is produced. That initially cold water could be reclaimed for plant watering or cold-water uses.

Owners like its small size, and several say it was easy for an experienced do-it-yourselfer to install since it uses standard venting. Some users had problems with the amount of hot water produced (too much or too little) or the time it took for hot water to reach a second-floor bath. Many of the complaints seem common to tankless water heaters in general.

We also found quite a few comments for Takagi tankless water heaters, in particular the Takagi T-K2 (*est. $900) natural gas water heater with up to 185,000 BTU input. This model is similar to the larger Bosch unit, with a 3.4 gpm flow rate for a 90-degree temperature rise and up to 6.2 gpm at a 50-degree temperature rise. Like all tankless water heaters, it takes about ¾ gallon of water before you get running hot water. We found the largest number of reviews from owners posting comments to the Berkeley Parents Network and to Greenbuilding.com, a site for environmentally conscious contractors and do-it-yourselfers.

As with other tankless water heaters, installation can be tricky, and a retrofit can get expensive. You need a ¾-inch supply line for water and special 4-inch stainless steel venting. Overall, reviews say this is a job best left for a professional, and it will be better if it's a clean install rather than a retrofit. As with other tankless heaters, some owners complain about waiting a long time to get hot water, especially in areas farther from the water heater. Like the Bosch unit above, the Takagi T-K2 uses natural gas for heating fuel, but needs an outlet to run the controls and onboard computer.

For all-electric homes, Keltech's Acutemp has electronic heating controls that save energy, a remote temperature dial and a limited lifetime warranty. Bosch's small electric PowerStar AE115 (*est. $500) has a solid copper heat exchanger and copper-covered heating elements. The PowerStar has a 95 percent EF, external temperature control knob, and a flow sensor that offers a steady output temperature. This model isn't recommended for areas where groundwater temperatures are lower than 60 degrees Fahrenheit, which means it's not appropriate for anywhere north of about mid-Arkansas. This model needs a 240-volt outlet. Consider the PowerStar AE125 (*est. $630) if you have colder groundwater temperatures.

Amazon.com is one of the few places to find some reviews on tankless water heaters, though many models sold there do not yet have any comments from owners. Still, the site hasn't been selling water heaters for very long, so reviews will surely begin to build up.

Solar water heaters

Solar water heaters use the sun's energy rather than electricity, oil or gas to heat water. They reduce your monthly utility bill and eliminate the pollutants and greenhouse gases emitted by fossil fuels produced when natural gas or oil is burned. Solar water heaters were popular in the '70s and '80s, but homeowners who had invested in these systems were left stranded when the federal government pulled the plug on solar incentives. Recent tax credit legislation, however, has improved this situation to make those systems more financially attractive. The Energy Policy Act of 2005 was the first major federal government program on energy in the past 13 years, and it gives tax credits far beyond the solar-only credits that started during the Carter administration and ended at the end of 1985.

All solar water-heating systems contain collection, storage and transfer components; some systems combine all three into a single unit. Some solar water heaters use pumps and others are called thermosiphoning (no-pump) models. A pump-type solar water-heating system usually has an insulated water tank in the utility room or basement or just a heat exchanger coil in a water heater. Temperature sensors in the solar collector and the water tank decide when the water circulation pump should run. In cold-weather climates, these systems have some sort of freeze protection. Thermosiphoning (also called passive solar) models are the least expensive. With a thermosiphoning system, the water storage tank is located above the solar collector on the roof (which may need to be reinforced to handle the extra weight).

Flat-plate collectors are the oldest solar water-heating technology, but are still valuable. Evacuated-tube designs are a newer technology. The sun shines through a glass tube onto the water and the vacuum around it reduces the heat loss. The advantage of any solar water-heating system is energy conservation and a reduction in water-heating costs of between 60 and 95 percent (depending on the system). The downsides are high initial cost and an involved retrofit and installation. You can plan on investing a minimum of $2,000 before installation. Most systems will cost between $3,000 and $6,000 installed. And solar water heaters may not completely replace electric or gas water-heating systems. These conventional systems are still necessary as supplements. Many solar water-heating systems are designed to preheat water that goes to a backup heater -- typically a conventional gas or electric water heater.

There are different types of systems for different climates. A closed-loop system circulates antifreeze through the system's tubes, protecting it from freezing. An open-loop system circulates water through the tubes, and is best for warm climates where freezing isn't an issue. Going solar isn't for everyone, and it's a lot more difficult than simply replacing a worn-out tank water heater. A level of commitment goes along with installing a solar heating system. Aside from saving money on monthly energy costs, you can reduce your personal contribution to global warming by up to 18 tons of greenhouse gas emissions over the life of the system.

We didn't find any performance reviews or comparisons of solar heating systems. Your best bet may be to first find a contractor who's experienced with solar systems. Depending on where you live, that may be the biggest challenge. The solar contractor should be a member of the Solar Energy Industries Association (seia.org). You'll also want to make sure the solar heating system you choose carries an OG300 rating by the Solar Rating and Certification Corporation (solar-rating.org). That's necessary to take advantage of the EPACT tax credit.

Manufacturers of solar heating systems include ACR Solar Roofs, Alternate Energy Technologies, Apricus Solar, Heliodyne, Solahart Industries, SunEarth, Taylor Munro Energy Systems, Thermo Dynamics and Thermomax USA. James Dulley's website has a good article and information on solar heating system manufacturers, which covers features and specifications of major brands. Here, we've listed a few of the distinguishing features of each brand's systems.

ACR offers both open- and closed-loop systems. The collectors are lightweight, and the polycarbonate cover is lighter and safer than glass. Systems come with a ten-year warranty. The modular design makes your solar system upgradeable, so you can start with one panel and add more as needed.

Alternate Energy Technologies' Eagle Sun line of 80- and 120-gallon solar water-heating systems are designed for smaller families. The EagleSun includes an electrical backup so the system can work on sunny and cloudy days. Other systems are available for larger families as well.

Heliodyne's "Gobi" collector looks like a skylight. Its special absorber coating operates efficiently in the winter. Heliodyne's systems are designed for the do-it-yourselfer, with included mounting hardware, modular kits for sloped roofs and tilt-up racks for flat roofs or ground installations.

Solahart Industries has developed a new absorber panel to allow more surface area to be exposed to the sun, improving efficiency. The Free Heat series is a closed-circuit system; water is only held in the storage tank. Solahart is an Australian company. In North America, Solahart is part of Rheem/Ruud.

SunEarth's "SunSiphon" is a Thermosiphon unit -- a passive design with collectors and storage tank. Available in both open-loop (for warm climates) and closed-loop (for cold climates) configurations, it relies on natural water circulation as opposed to the pumps and controllers found in active systems.

Taylor Munro Energy Systems' SunCoil is an active year-round solar water-heating system that can be customized to heat water for hot tubs, swimming pools and other applications. They also offer Sunwell -- a three-season passive solar water-heater system consisting of a stainless steel tank and a parabolic reflector inside an insulated, glazed housing.

Thermo Dynamics Ltd. offers the Solar Boiler, a preheating system that is used in conjunction with the homeowner's conventional water heater. Cold water enters the Solar Boiler for initial heating, and is then delivered to the backup or heating system for final heating as required. The conventional system is typically fueled by oil, electricity, propane or natural gas.

Thermomax Evacuated Heat Pipe Solar Collectors (tubes) function differently than the other types of collectors. Consisting of a heat pipe inside a vacuum-sealed tube, the solar energy is concentrated on the top of each tube and diverted through a manifold to a storage tank or load. Thermomax collectors are available for all types of climates, including regions with cold winters and high humidity tropics. Apricus Solar also uses glass solar tubes instead of flat panel collectors. Reviews say this type of system is more efficient, with less heat loss.

Calculating water-heater efficiency and payback

Efficiency for tank-type and tankless water heaters is rated by energy factor, or EF. This number is calculated by dividing the energy delivered as hot water by the amount of energy consumed to produce the hot water. If no energy was lost and it all came out as hot water, the heater would have an EF of 1.0. Most conventional gas water heaters have an EF of around .59. On-demand (tankless) gas heaters are typically rated between .81 and .85, making them on average about 40 percent more efficient than conventional models.

How long does it take to recoup installation costs by energy savings? To estimate the annual operating cost of a tank-type or tankless water heater, you need to know the energy factor (EF) of the heater you're considering, along with the fuel type you want to use and your local fuel rates. These calculations are based on water usage of about 64 gallons per day.

For gas and oil water heaters, you need to know the unit cost of fuel by BTU (British thermal unit) or therm (1 therm = 100,000 BTU). Then use the following calculation:

365 X 41045/EF X Fuel Cost (BTU) = estimated annual cost of operation

OR

365 X 0.4105/EF X Fuel Cost (therm) = estimated annual cost of operation

Example: A natural gas water heater with an EF of .57 and a fuel cost of $0.00000619/BTU:

365 X 41045/.57 X $0.00000619 = $163 per year.

For electric water heaters, you need to know the unit cost of electricity by kilowatt-hour (kWh). Then 365 X 12.03/EF X Electricity Cost by kWh = estimated annual cost of operation.

Once you know the purchase and the annual operating costs of the water-heater models you want to compare, you can use the table below to determine the cost savings and payback of the more energy-efficient model(s). Source: U.S. Department of Energy, Energy Efficiency and Renewable Energy, http://www.eere.energy.gov/.

The payback period will be shorter if energy prices continue to rise or if the homeowner uses more than 64 gallons of water per day.

Important Features: Water heaters

Experts say to consider the following when shopping for a water heater:

• For a standard tank-type water heater, proper insulation reduces standby losses. If you are buying a gas water heater, make sure the insulation rating is R-16 or better. For electric water heaters, look for R-22 or more. Models with a longer warranty usually have 2 inches of foam insulation. Those with a shorter warranty often have 1 inch of insulation.

• For tank-type water heaters, a longer warranty usually indicates better insulation. Consumer Reports found that there is a direct relationship between warranty length and better insulation, heat transfer and larger heating elements. Look for longer coverage, particularly if you have hard water and use water softeners, since these factors can more quickly corrode the anodes.

• If you are replacing a tank water heater, the easiest replacement will be a similar tank water heater. Changing types can result in more expensive refit costs. Those costs may eventually be recouped by energy savings, but you'll need to do some math.

• Tankless water heaters are more efficient than tank water heaters, but reviews say they take some getting used to. If you want to switch to a more efficient tankless water heater, be aware that you'll need some time to adjust, since water delivery is different than with a tank water heater.

• Flow rate of hot water from a tankless system is greatly affected by the temperature of your groundwater. The warmer your groundwater, the better the flow rate. Homes in colder climates will need a larger system to get an adequate hot-water flow rate. The average groundwater temperature in the U.S. is about 50° Fahrenheit. Most people like shower temperatures of between 105° and 120°, so your groundwater temperature would need to be raised by 60° to 75°.

• Installation of a tankless water-heater generally works better for new construction. Retrofitting may involve installing new gas pipes, new plumbing and other changes.

• Solar water-heating systems are most efficient, but are also most expensive to buy and install. Federal tax credits for installing solar systems are also available -- up to 30 percent of the cost of the system up to $2,000.

• Federal tax credits are available for installing more energy-efficient tankless water heaters. Currently, you can receive a $300 federal tax credit if you install a water heater with an energy factor of .80 and higher. Many (but not all) tankless water heaters fit this criterion.

Storage (tank) water-heater sizing and first-hour capacity

To determine tank size, estimate your peak-hour demand (PHD) -- the number of gallons of hot water your home requires during its busiest hour. Use the table below to calculate the gallons needed for each shower, laundry load, etc. during that single peak one-hour period.

This table does not estimate total daily hot-water usage. As an example, an average of 4 gallons of hot water is used each time dishes are washed by hand, but dishes washed by hand are usually done more than once each day. The average daily hot-water usage for hand dishwashing, 12 gallons, is about the same as the average hot-water usage for an automatic dishwasher used once a day.

Source: Consumers' Directory of Certified Efficiency Ratings for residential heating and water heating equipment from GAMA (Gas Appliance Manufacturers Association)

EXAMPLE: Your household uses the most hot water in the morning. In the busiest one-hour period of the morning, the usage is:

In this case, the peak hour demand is 70 gallons. You should look for those models of water heaters with a first-hour rating of between 68 to 72 gallons. Many 40-gallon water heaters have an FHR in this range.

Sources: http://www.consumersearch.com/www/house_and_home/water-heaters/index.html and http://www.consumersearch.com/www/house_and_home/water-heaters/review.html