THIS website has several workshops, including a couple for building your own solar water heater! The hands-on experience would, no doubt, be worth the money spent, and much of the cost can be paid by work exchange.

The Sustainable Village has a 30-gallon passive solar water heater kit that looks like it wouldn’t be difficult to assemble. Kits would definitely be easier than starting from scratch, even if it is a bit pricier.

There are a couple of popular websites that instruct their readers in how to make their own passive water heater. One website, Instructables, gives step by step instructions for making your own solar thermal water heater for less than $5, if you’re willing to go rummaging for your materials. The other website, probably even more well known, is taking forever to load… Anyway, Mother Earth News, tells how to build your own passive solar water heater.

The benefits of building your own solar water heater are immediately seen. Compare the cost of a normal water heater, or even of conventional solar water heaters, to that of the water heater you could build. Although you may not be able to provide your entire household’s hot water with these, it could certainly reduce some of your energy costs.

Let’s look at some of the pros and cons of heat pump water heaters.

First, some advantages…

• As mentioned in the previous article about heat pump water heaters, fuel efficiency: these units have lower operating costs, using only 33-50% of the electricity that other electric water heaters use.
• If you live in a warmer climate and use electricity to heat water, a heat pump may be your best choice for efficient energy use.
• Cool exhaust air can be exhausted into the room–possibly helping to cool the room in summer–or to the outdoors.
• The life expectancy is 20 years. Of course, as with most appliances, proper installation and maintenance can extend the life expectancy significantly, and can reduce losses in efficiency.

Now, some disadvantages…

• Heat pump water heaters are most effective in mild climates—a 40-90-degree temperature range year-round is needed for effective use; they will not function efficiently in a cold space.
• They have higher initial costs—purchase and installation–than conventional storage water heaters.
• If the heat pump is not in a warm area from which to pull heat, the recovery rate can be modest, variable, and relatively low.
• This makes use of a storage system, so there will be stand-by heat losses.
• If the water pump is installed in a heated room, it will steal some of the heat, thus heating that room becomes less efficient.
• These are rather complex to install, especially if the heat for the unit is brought in from a remote site or if a separate tank is used. It is probably best to hire a contractor.
• Heat pump water heaters are not widely available, possibly because of lack of demand due to initial cost. Also, lack of contractor and consumer awareness of this option has led a number of manufacturers to discontinue their lines of heat pump water heaters. (Sounds like a marketing problem!)

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The most commonly known use of heat pumps is to heat and cool homes. But they can also be used to heat water, either in combination with a home heating/cooling system or as a stand-alone water-heating system. Because this type of water heater does not generate heat, but instead moves it from another source, it is more efficient than most other types of water heaters, using 33-50% of the energy required for a conventional electric storage tank water heater.

A stand-alone heat pump water heating system can be purchased in two different ways: either with a built-in water storage tank (an integrated unit) or as an add-on to an existing water heater tank. The heat-pump, which has a life expectancy of up to 20 years, may outlast the tank, so the add-on may be the wiser choice, if it is an option.

Heat pump water heaters, for which electricity is the only fuel choice, use a compressor and a refrigerant fluid to transfer heat from air in the general vicinity of the heat pump to heat the water. They work better with warmer air, since they don’t have to work as hard to extract heat from the air source. Some better models can bring in warm air from an attic or from outdoors. For highest operating efficiency, they should be installed in a high-heat room, such as a furnace room. There are some geothermal models that take heat from the ground in winter and from indoor air in the summer. According to another source, this type is good for most locations, but an air heat pump is good only for warm climates with winters that are quite mild.

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We previously learned about some of the advantages of demand water heaters. Now let’s look at some disadvantages.

Disadvantages: a limited flow rate, which can cause difficulty keeping up with large demand; initial cost is a bit more than storage tank water heaters.

The typical flow rate with a demand water heater is two to five gallons per minute. If your household does not use hot water at more than one location at a time, this might be sufficient, but if someone is going to take a shower while the dishwasher is running, the water heater is not going to be able to keep up.

Gas tends to have a better flow rate than electric, however there is a constant, albeit small, energy loss with gas because of the energy consumed by the pilot light.

One way to combat this flow rate problem is to install demand water heaters in parallel sequence for simultaneous hot water demands. Or multiple demand hot water heaters can be installed.

At best, some manufacturers claim their product can perform as well as a 40-gallon storage tank water heater.

As stated in a previous article, the initial cost of a demand water heater is higher than that of a conventional storage tank type, but the future savings on monthly utility bills could make up for that.

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Like all water heaters, demand water heaters have advantages and disadvantages. For now, we’ll consider some of the advantages.

Advantages: low standby losses, as stated above; low operation costs–a possible 10-50% decrease in energy consumption for heating water; hot water is always available; long life expectancy; good for do-it-yourselfers; no tank to maintain or leak in the future.

Concerning energy savings, for homes that daily use no more than approximately 40 gallons of hot water, demand water heaters can be 24-34% more energy efficient than conventional storage tank water heaters; for 86+ gallons-a-day households, 8-14% more energy efficient; up to 27-50% more energy efficient if a demand water heater is installed at each hot water outlet.

Hot water is always available as long as your water supply lasts and the energy to heat it is available, though the low flow rate may take away some of the appeal of this. This will be discussed in a later article on the disadvantages of demand water heaters.

The life expectancy of a demand water heater is 20+ years, as compared to 10-15 years for a conventional storage tank water heater. These 20 years can be extended for many more years by having easily replaceable parts and by periodic maintenance, which also helps maintain efficiency.

Although, as one would expect, it is not suggested, it is possible for the do-it-yourselfer to install a demand water heater. Of course, the manufacturer should be consulted and should be able to provide you with installation and instruction manuals. (If you are considering a gas unit, you will need to consult with an experienced contractor to find out if your gas supply is sufficient and proper venting is possible.) And don’t forget to check with your local government concerning a permit, if needed, and local water heater installation codes.
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Stand-by heat-losses associated with conventional storage water heaters are eliminated with demand (or instantaneous) water heaters, which heat the water as it is needed.

With a demand water heater, when a hot-water tap is turned on and water begins to flow, a heat exchanger is activated. The water runs into the water heater unit, passing through the heat exchanger, where it is heated by an electric element or a gas or propane burner, and is then sent to the tap.

This type of water heater generally has a higher purchase price than a conventional storage water heater, but lower operating and energy costs which could offset the purchase price¹.

Demand hot water heaters perform better when you take steps to use water efficiently, such as installing modern low-flow faucets and showerheads. Also, hot water locations in your home should be close together, and close to the demand water heater; if they are spread out, multiple heaters may be called for, thus raising initial costs.

For a slightly different slant, rather than being your primary source of hot water, a demand water heater can be used as a booster for washing machines, dishwashers, solar hot water systems, or wood-fired hot water systems².

We’ll learn more in future posts about advantages and disadvantages of demand water heaters.

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The life of a conventional storage water heater is generally determined by the tank, which usually rusts through within 10 to 15 years, thus calling for a replacement. (Source #1)

Previously, tanks were made of copper, were very resistant to corrosion, and could last decades. They are now made of glass- or porcelain-lined steel, and can rust and leak. Sacrificial anode rods made of magnesium or aluminum alloy are installed in these to help prevent this. These rods undergo galvanic corrosion to reduce corrosion of the steel tank. The longer the guarantee on a tank, the more anode material in it. The tank will rust, however, when the anode is used up, although you may be able to check the anode, and, when needed, replace it. (Source #2) These should be checked and probably replaced every five years, which is the life expectancy of the anode rods. (Source #1)

Plastic tanks are available in some electric water heaters. These are designed with materials that are corrosion-free and corrosion-resistant. They could, in theory, last as long as the home.

Regular (at least annual) maintenance of conventional storage water heaters involves draining the bottom of the tank of accumulated sediment, helping to maintain efficiency and extending the life of the tank. (Source #2)

This is the most common type of residential water heater used in the United States today. It provides a ready tankful—20 to 80 gallons, normally—of hot water, which is drawn from the top of the tank when a hot water tap is turned on. Cold water enters the bottom of the tank to replace the hot water that has been drawn off, so that the tank is always full (although not always of hot water!)

Fuel sources for this type of water heater include natural gas, propane, fuel oil, electricity, and solar energy.

Some energy is necessarily wasted with this type of water heater since the water in the tank is constantly heated, even when there is no hot-water demand. This is known as stand-by heat loss. Newer models have less stand-by heat loss and, therefore, lower operating costs because they are better insulated than older tanks. If you are shopping for a new storage water heater, look for one with an R-Value (thermal resistance value) of not less than R-12. Some have an R-Value as high as R-25.The better-insulated tanks have a higher purchase price, but the price can be quickly recouped, depending on your specific use-patterns and energy costs. To help determine your most energy-/cost-efficient choice, check the Energy Guide label (which is required on storage water heaters) for either the annual estimated system-operating cost or for energy efficiency ratings.

If you currently have an older tank and want to increase energy efficiency, you can add an insulating blanket to the outside of the tank to reduce heat loss. The blanket must be the properly sized for your specific tank and not block safety or drainage valves, controls, or airflow. Adding an unnecessary insulation blanket, particularly in very humid locales, can cause condensation problems, possibly leading to mold or rust.

According to one source, (which I believe is not from the United States, so I’m not sure this is an option in the U.S.), efficiency can be increased if you have an intelligent electrical power distribution, heating the water when the power demand is low and turning off when it is high. “This could be implemented by allowing the power supplier to send load-shedding requests, or by the use of real-time energy pricing.”

Keep in mind that smaller tanks have less surface area, and therefore, less heat-loss, which can be 10-15 percent of the water heater’s operating cost, although, as indicated above, the more insulation, the less the heat loss.

Also, if the storage water heater is located in the home’s heated/cooled space, heat loss from the water heater can actually contribute to heating the home. However, in the months when the home is cooled, it also contributes heat, thus creating a larger cooling load. Often, this type of water heater is located in non-heated/non-cooled areas of the home, and therefore does not affect the temperature inside the home, but instead simply loses the heat to the outside air.

Also keep in mind that the space you have—where the water heater will actually be installed–may limit your choices. However, storage tanks come in a number of sizes and proportions, thus accommodating a fairly wide variety of space considerations.

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Below is a brief, helpful summary of the five main types of water heaters available, based on information from the Department of Energy. Future articles here will provide more specifics about each type.

1. Conventional storage water heaters

This type of water heater has a storage tank full of (usually) ready-to-use hot water.

2. Demand water heaters (also called tankless or instantaneous)

These heat water on-demand; no storage tank is required.

3. Heat pump water heaters

Heat pump water heaters take heat from another source, such as the surrounding air, and put it (at a higher temperature) into a tank where it will heat the water.

4. Solar water heaters

Obviously, these heat water with heat from the sun.

5. Tankless coil and indirect water heaters

This type heats water using the space-heating system in the home.

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Some information about a water heater is easy to find on labels if you know where to look and how to interpret it.

ENERGY STAR. Do not look for an ENERGY STAR label. The U. S. Department of Energy is working on creating an ENERGY STAR residential water heater program, but at this time (latest information found is from October, 2007), the ENERGY STAR program does not address water heaters. As a matter of fact, “water heating is the only major residential energy end use that the ENERGY STAR program does not address.” (source 1)

Price tag. Most, if not all, major appliances have two price tags: one shows the purchase price; the other, the lifetime-operating cost of the appliance.

EnergyGuide label. Most appliances have an EnergyGuide label (a bright yellow and black label that tells the operating cost of the appliance) so that the consumer can easily compare different models and make a more informed purchasing decision.

The first-hour rating (FHR), or recovery rating, of a water heater can be found on the EnergyGuide. (source 2). Indicating the amount of hot water that the water heater can deliver during peak hot-water use, this information is actually more important than the more-commonly considered tank capacity. (source 3)

Energy Factor (EF). Often listed beside the EnergyGuide, EF is a measure of the efficiency of the water heater, taking into account recovery-efficiency, standby losses, and cycling losses. The more energy efficient the water heater, the higher the EF.

Water heater label. Labels on water heaters vary, but some of the information often included are manufacturer; model and serial numbers; R-value (insulation rating); capacity; manufacture date; and the Btu input rating, which indicates how powerful the water heater is. (source 4)

Heating water in a home, on average, uses 13% to 25% of the energy consumed in that home. Depending on your source of information, it is the second (1) or third (2) largest consumer of residential energy, being topped only by space heating and cooling, and possibly by kitchen appliances.

A number of factors should be considered when choosing a water heater, including (but not limited to) energy efficiency; type of fuel and its cost and availability in your area; size/capacity; cost, taking into account the purchase price and the cost of installation; and the space you have provided for the system. Your climate and environment, including the position of your home, should also have an impact on your choice, particularly when considering a heat pump water heater, a tankless coil water heater, or a solar water heater. Another factor is ease of installation: will this be in a new-construction or is it a retro-fit?

Among the types of water heaters available today are storage, or tank-type; tankless; demand (or instantaneous); heat pump; natural gas; propane; oil; electric; and solar, each type having its own advantages and disadvantages.

Future posts will examine the types of and considerations about water heaters in more detail.

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