Solar water heaters—also called solar domestic hot water systems or solar thermal hot water systems—may be a cost-effective way to generate hot water for your home or office. Solar water heating systems include storage tanks and solar collectors. The system uses pumps to circulate a non-freezing fluid through the collectors and a heat exchanger. The liquid heats the water in the tank and circulates back to the collector. Since most solar hot water systems can’t be relied upon to provide hot water during cloudy or snowy months, or times of high hot water demand, Vermonters generally use a backup system as well. Two types of solar collectors are most common in Vermont:
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Flat-plate collector: Glazed flat-plate collectors are insulated, weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-plate collectors—typically used for heating swimming pools—have a dark absorber plate, made of metal or polymer, without a cover or enclosure.
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Evacuated-tube solar collectors: These feature parallel rows of transparent glass tubes. Each tube contains a glass outer tube and metal absorber tube attached to a fin. The fin's coating absorbs solar energy but inhibits radiative heat loss.
Not all systems are appropriate for all buildings and not all buildings are well suited for solar. Panels are typically most effective when they are installed where they will receive at least eight hours of daylight without shading, and positioned no more than 45 degrees from true south.
Some Benefits
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No combustion or venting needed
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Renewable energy source
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ENERGY STAR® rated options
Some Considerations
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May produce more than you need in the summer, and not enough in the winter
- Solar typically requires proper exposure to the sun and a back-up hot water system
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Possible overheating of the storage tank
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Need to keep exchange fluid from freezing
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You may want to consider and compare the cost-effectiveness of installing a solar thermal hot water system versus solar PV with a heat pump water system
Some Next Steps
If you are interested in solar hot water, the following steps may help you determine if it is right for you and your property:
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Estimate the cost and energy efficiency of a solar water heating system
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Evaluate your site's solar resource
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Determine the correct system size
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Investigate local codes, covenants, and regulations
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Understand the components of a solar water heating system, including the heat exchangers and heat-transfer fluids
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Review the system’s controls to ensure overheating will not be an issue
The Department of Public Service publishes “A Vermonter’s Guide to Residential Solar,” which homeowners may find helpful. That guide can be found, along with other Renewable Energy Resources, by visiting the Department's Resources website.
Learn More
Visit the pages below to learn more about different types of Hot Water systems:
