Warming your Water with Sunshine

The feeling of fresh, warm water on your face in the morning shower is soothing, refreshing and invigorating.  The feeling of sunshine on your shoulders is equally therapeutic – in modest doses of course.  Imagine combining these two to naturally warm water with sunshine, and you have a match made in heaven.

We’ve actually been doing this for years – at least in the summer and in warmer climates.  Some of the earliest versions of solar water heaters were simply metal tanks sitting out in the sun in the southwestern United States.  The Climax brand solar water heater was first marketed in California in 1890.  By the 1950’s, half of the homes built in south Florida had a solar water heating system.  But when the utilities started promoting cheap energy, the systems were no longer cost-effective.

These original systems were only practical in the warmer climates, because the thermo-siphon systems can’t survive a hard freeze.  So, rather than heating the water directly, a separate heat transfer fluid (typically glycol) is used to capture the warmth from the sun and circulate that through a heat exchanger in the hot water storage tank.  This closed-loop system is the most common way of heating water with solar energy.

Solar water heating systems used to be practical but not pretty.  In earlier models, both the tanks and collector panels were mounted on a south-facing roof.  These systems tended to be clunky and visually unappealing.  As the closed-loop systems became more common, insulated storage tanks were installed indoors.  The most efficient collector panel is made of evacuated tubes, which have a vacuum seal and virtually no heat loss.  These work better in colder climates and on overcast days, and are well suited for commercial or heavy-duty applications.

Most residential applications use flat collector panels.  Velux, a long-time maker of skylights, developed a closed-loop solar water heating system with collector panels that look like skylights.  In addition to the high value placed on aesthetics, these collectors are more easily installed, less expensive, more durable and require less maintenance.  They are very efficient, and work all year, including the cold days of winter!

The size of the system is largely dependent on the number of residents of the home.  For one or two people, a single collector panel can be used with a 60-gallon storage tank.  For larger families, the systems can be scaled up to accommodate the greater volumes of hot water.  A control station maintains the temperature to a pre-set degree, typically 120-140° F.  During periods of extended cloudy days or heavy usage (such as with overnight guests), supplemental energy from an electric or natural gas backup heating system kicks in to bring the temperature up to the desired level.

Solar energy is a very cost-effective and reliable means of heating your water.  The systems require very little maintenance, and typically reduce water heating bills by 50-80%.  If you have a gas water heater and furnace and electric oven and stove, you can determine the how much gas is used to heat water when the furnace is off.  A general rule of thumb, though, is that about 20% of your total energy consumed is used to heat water.

Prices typically range from $6,000-$10,000, but solar water heating systems qualify for the 30% federal tax credit that makes them much more affordable.  In areas where energy prices are high, the payback with incentives can be realized in as little as three years.  In the Midwest, where energy is relatively inexpensive, the payback is closer to 10 years.  When calculating payback, you need to take future increases in the cost of energy into consideration.  Talk to a qualified installer to find out more about how this system can work for you.

There are a lot of ways to harness the clean, renewable energy of the sun.  Heating your water is one of the most natural and cost-effective ways to do it.  Just think:  one morning as you’re enjoying that warm shower, you’ll get a little sunshine along with it!

This was published in the Going Green section of the August 2010 issue of Spirit Seeker magazine.