Can you tell me how well solar hot-water heaters work?


Can you tell me how well solar hot-water heaters work?

Asked by Betsy Humes, Brooklyn, NY

I recently heard about solar hot-water heaters for the first time. Apparently they are more affordable than a traditional photovoltaic panel system for electricity. Can you give me more details about what these systems are, how they work, and how much they cost? Finally, is there anyone in my area doing installations?

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Paul Rosen's picture

Solar water heating has been around since the Mayans used stones heated by the sun to warm their sacred baths. A well-designed solar thermal water-heating system can operate efficiently practically anywhere in the United States.

  • The moderate to warm climates of the southern and western parts of the U.S. are well suited to the traditional flat-plate collector.
  • For the parts of Europe and the U.S. with colder climates, the evacuated tube hot-water solar collector is quite efficient.

A solar thermal water heater is 60-70% efficient in collecting the sun's energy, whereas the average photovoltaic system is in the neighborhood of 14-20% efficient in converting the sun's energy.

  • As a result, heating water with PV usually does not make economic sense.
  • Additionally, a solar water heater can operate efficiently even where there is some shading, while a PV system's performance is significantly reduced when partially shaded by adjacent buildings or trees.
  • Many homes that won't support an efficient PV system can produce a good amount of hot water with a thermal system.

For a family of four, a solar water heater supplying 50-70% of the domestic hot water should cost $6,000-$8,000. The payback can be as short as five or six years.

Check GreenHomeGuide's Find A Prodirectory tofind solar installers near you.

For more information:

The Department of Energy publishes an online Consumer's Guide to Energy Efficiency and Renewable Energy that includes a good explanation of solar water heaters.

YouTube has a video of a solar hot water installation.