Q: How does a solar water-heating system work?
A: Every solar water-heating system features a solar collector that faces the sun to absorb the sun's heat energy. This collector can either heat water directly or heat a "working fluid" that's then used to heat the water. In active solar water-heating systems, a pumping mechanism moves heated water through the building. In passive solar water-heating systems, the water moves by natural convection. In almost all cases, solar water-heating systems work in tandem with conventional gas or electric water-heating systems; the conventional systems operate as needed to ensure a reliable supply of heated water.
There are many types of solar water heaters. Each has strengths to recommend it for specific climates and water conditions. Solar system professionals can help you select the most appropriate system for your area and your needs.
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Q: Are there any disadvantages to using solar energy?
A: The energy in sunlight can be used for many purposes, including heating water for a building or swimming pool. And using solar energy has many environmental and life-cycle economic benefits. However, solar energy heating or solar electric products often have higher "first costs" than other, similar products do. This means it will probably cost more initially to purchase and install a solar system than it will to purchase and install another kind of heating or electric system. Still, in nearly all cases, you will recover your initial costs through substantial fuel savings (as shown in lower utility bills) over the life of the product. Many solar systems last from 15 to 30 years.
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Q: Can a solar water heater replace an electric or gas water heater?
A: Not completely. Conventional electric or gas water heating systems are still necessary as a supplement to the solar water heating system, largely because the sun might not shine in a particular area for several days at a time. However, because solar water heaters are designed provide hot water directly to the tank of a gas or electric water heater, they reduce the need for the water heater to run on conventional fuels. And this in turn reduces your gas or electric bill. Depending on where you live, solar water heaters can provide up to 80% of your home's annual water-heating needs.
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Q: Can solar water heaters be used in northern states and other colder climates?
A: Yes. Solar water heating technology is effective regardless of the outside temperature. In colder climates, more energy is required to heat cold incoming ground water, so using solar energy in such conditions could dramatically lower a consumer's utility bills. In addition, colder incoming ground water helps solar water heaters to operate at higher efficiencies.
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Q: Can I use a solar water-heating system to heat my swimming pool?
A: Using a solar system to heat a swimming pool is the most common use for solar energy in the United States today. Solar pool-heating systems increase an unheated pool's water temperature by 10 degrees or more, and they can extend the swimming season by two to three months. Solar system prices range from $2,500 to more than $5,000, depending on the size of your pool and other conditions, such as shading from nearby trees and buildings and how close the pool is to the ocean. When solar systems replace a conventional gas or electric swimming pool heater, the initial investment can usually be recovered in about three years or less, because of reductions in subsequent utility bills.
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Q: Can solar power be used to heat my home and business?
A: No pre-engineered residential solar space heating systems are readily available to consumers today. But many solar energy professionals can engineer a system for you, on request. However, solar space-heating systems are considerably more expensive than solar water-heating systems. Depending on the size of the space that needs heating, a solar system could cost anywhere from $3,000 to more than $10,000. A solar energy professional in your area can explain what would be involved to purchase this type of solar system. You may want to consider increasing your insulation and using passive solar technologies-such as large, energy-efficient, south-facing windows-as an alternative.
Other Resources: To learn more about energy-saving options, please visit DOE's Energy Savers Web site and contact the Sustainable Buildings Industries Council (202-628-7400).
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Q: Aren't solar water heaters bulky and unattractive?
A: In the 1970s, solar water heating technology was being developed and installed quite rapidly in response to that decade's energy crises. At that time, efficiency and ease of installation were the priorities, often at the expense of appearance. Many people thought that roof-mounted solar collectors were unsightly, even though they helped to reduce the amount of unsightly smoke billowing from coal-fired power plants! Still, the resulting attention to aesthetics has resulted in the "skylight" look of many of today's solar collectors.
Other Resources: To learn more about solar hot water-heating systems, please visit our solar hot water technology section.
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Q: What about heating my swimming pool with solar?
A: Solar swimming pool heating is the most common way that people in the United States utilize solar energy today. Solar pool-heating systems increase water temperature by 10 degrees or more over an unheated pool, and can extend the swimming season by two to three months. System prices range from $2,500 to more than $5,000, depending on the size of your pool and on other conditions such as shading and proximity to the ocean. When systems are installed to replace a conventional gas or electric swimming pool heater, the initial investment can usually be recovered in approximately three years, sometimes less.
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Q: Can solar power be used to heat my home and business?
A: While there aren't any pre-engineered residential solar space heating systems available on the market, solar energy professionals could engineer a system for you. However, these types of systems are considerably more expensive than solar water-heating systems and, depending on the size of the heated space, could range from $3,000 to more than $10,000. A solar energy professional in your area can help you understand what would be involved in this type of solar system purchase.
You may want to consider increased insulation and passive solar technology. For this, we recommend you contact the Sustainable Buildings Industries Council (202-628-7400) or DOE's Energy Savers Web site.
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Q: What are the benefits of using solar energy to heat water in my home?
A: First, the fuel is free! Once you recover the higher initial costs of a solar system through reduced or avoided energy costs (that is, lower utility bills), your solar system will require expenditures only for maintenance. And when you include the cost of a solar water heater in a mortgage on a new home, the system often provides a positive monthly cash flow from the first day of ownership. The Solar Buildings Program offers a free software program that allows you to determine how much money you'll save by installing a solar water heater in your new home.
Second, solar water heaters and other solar technology applications do not pollute. They do not add to the carbon dioxide, nitrogen oxides, sulfur dioxide, and other air pollutants and wastes produced by most of today's power plants, even those that run on natural gas. And they allow you to burn less natural gas in your home, as well.
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Q: How much does a solar water-heating system cost?
A: Unfortunately, there is no one answer to this question. The cost of a solar system depends on a number of factors, such as the size of the system and the particular system manufacturer, retailer, and installer. However, any solar rebates and other incentives available in your area will reduce that total cost.
For solar water heaters and space heaters, you will also be taking into consideration the price of the fuel used to back up the system. In most cases, you will have to add in the cost of supplemental natural gas or electricity to get a fairly accurate estimate of how much you can expect to pay for a solar system.
Installed costs vary widely, from $1,500 to more than $3,000. Some home builders are beginning to list solar water heaters as an option for their homes. Others include them as a standard feature in every home. In some cases, the builder or mortgage company may offer a lower interest rate when solar water heaters or other energy-efficient features are built into a new home, because the buyer can expect to save a significant amount of money on future energy bills. Although a solar water-heating system still costs more than a conventional electric or gas water heater, some states and utilities offer rebates that can reduce the total cost appreciably.
Other Resources: To learn more about financial incentives in your area, please visit the Database of State Incentives for Renewable Energy (DSIRE) and contact your State's Energy Office . One caveat: any time you work with a contractor, it is wise to check references.
Your U.S. Department of Energy (DOE) regional support office may also be able to provide guidance.
To learn more about financing opportunities, please see The Borrower's Guide to Financing Solar Energy Systems: A Federal Overview, September 1999 (PDF 501 KB).
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Q: How much money will a solar water-heating system save on my utility bill?
A: It is difficult to say how much you will save with a solar system. That depends on several factors, including how much you already pay your local utility for electricity or natural gas. You can ask your solar system professional how much heat your new system will produce on an annual basis and then subtract that number from your current annual consumption—the total amount of electricity and gas you use—to get an idea of how much you will save. Data on your current annual consumption should be available from your utility.
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Q: How do I find out about financial incentives such as rebates or tax credits in my home state?
A: Several resources are available to help you obtain this information. To learn more about financial incentives in your area, please visit the Database of State Incentives for Renewable Energy (DSIRE) and contact your state's energy office. One caveat: Any time you work with a contractor, it is wise to check references.
Other Resources: For additional guidance, contact your U.S. Department of Energy (DOE) regional support office.
To learn more about financing opportunities, please see The Borrower's Guide to Financing Solar Energy Systems: A Federal Overview, September 1999 (PDF 501 KB).
Download Acrobat Reader.
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Q: Do you have any suggestions for school projects involving solar energy?
A: Some of the following documents are available as Adobe Acrobat PDFs. Download Acrobat Reader.
Numerous Web sites provide information about solar energy for consumers and for academic and educational purposes. Here are just a few:
Visit Sandia National Laboratory's Earth and Space Science educational pages.
Other Resources: Information about solar science projects is also available through these organizations:
The U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy has a young student-focused Web site called Dr. E's Energy Lab. The site contains fun ideas for student projects and energy-related learning.
The Energy Information Administration Kid's Page provides a wide selection of information to help children learn about energy.
The Florida Solar Energy Center has a renewable energy curriculum that is updated regularly. The material makes up a six-week, stand-alone science curriculum or can be used in individual class sessions. The curriculum gives complete details on more than 30 classroom presentations. There is no charge for the material.
The American Electric Power's Watts on Schools project offers information about solar energy and schools. For lessons and activities about solar and PV data collected from school solar energy systems, see.
See also the teacher programs on NREL's Education Partnership Web site.
The California Energy Commission's entertaining Web site, Energy Quest, provides energy information and educational materials for students, parents, and teachers.
And the Energy Center for Wisconsin has a list of books on this subject.
Schools Going Solar is a project of the Interstate Renewable Energy Council, and its aim is to bring solar energy to schools across the U.S..
The Alliance to Save Energy provides educational information about energy efficient technologies.
Finally, Stanford University's Solar Center site presents a collection of fun educational activities for children.
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