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What is Solar Energy?
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Solar energy is the radiation from the sun that reaches the earth. Using photovoltaic cells made from
silicon alloys, sunlight can be converted into other forms of energy, such as heat and electricity.
Solar cells can convert up to 22% of sunlight into electricity.
Solar thermal energy is currently used for heating water for domestic use and for heating building space.
Flat-plate solar energy collectors with a fixed orientation are generally used in these cases. Most consist
of a flat-plate absorber to intercept and absorb solar energy; a transparent cover to allow solar energy
to pass through; a heat-transport fluid flowing through tubes to remove heat from the absorber; and a
heat-insulating backing.
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How does a solar water-heating system work?
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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.
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Can a solar water heater replace an electric or gas water heater?
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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 to 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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Can solar water heaters be used in northern states and other colder climates?
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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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Can I use a solar water-heating system to heat my swimming pool?
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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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What are the benefits of using solar energy to heat water in my home?
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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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Aren't solar water heaters bulky and unattractive?
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In the 1970s, solar water heating technology was being developed and installed quite rapidly in response
to that decade's energy crisis. 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.
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How much does a solar water-heating system cost?
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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.
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How much money will a solar water-heating system save on my utility bill?
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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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How do I find out about financial incentives such as rebates or tax credits in my home state?
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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.
Sources:
Department of Energy
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