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Solar Water Heaters: A Primer

Hot water is one of the main “offenders” found each month hidden in your gas or electric bill.  In fact, for most households, hot water is the second largest chunk of overall energy use. And it’s relatively easy to see why. Hot water is a luxury many of us aren’t willing give up, no matter how self-reliant we want to be. We like our hot water for showers, laundry, washing dishes, and more.

In a single year, the average electric water heater costs $500 to operate. Natural gas water heaters do fare a bit better, averaging $400 in operational costs. That’s a hefty price to pay for the luxury of hot water. Other options are high-efficiency water tanks and tankless water heaters.  And don’t forget the solar option.

Solar water heaters are the ultimate in “going green.” Solar power is the cleanest and most renewable energy source we’ve got at our disposal. Solar power is free and gives off no toxins or dangerous gases when converted into energy for your home. Simply put, sunlight is in abundant supply… and isn’t owned by any power company!

Solar water heaters are popular because they are simple and uncomplicated. With a solar water heater, the sunlight doesn’t have to be converted into electricity (like you would need to power an appliance in your home). To enjoy hot water with a solar heater, you only need to heat the water. And turning sunlight into a heat source is very easy to do.

Ever left a glass of ice water or iced tea outside when working or gardening? All of us have at some point. In almost no time at all, the ice melts, and the once-cold beverage has warmed up. A solar water heater works in almost the exact same way.

The Mechanics of a Solar Water Heater

Solar water heaters have two main parts: the solar collector and a storage tank. (There are other parts and pieces, but for our primer’s sake, we’ll focus on these two areas first.) A solar collector is an insulated box-like structure that is usually glazed for optimum heat retention. The solar collector has one primary job: to harness the power of the sunlight, by turning radiation from the sun into heat for your water.  The storage tank then holds the warmed water.

There are two categories of solar water heaters – passive and active. An active heater uses electrical pumps to push the water through your system. The passive system does not. Instead, it uses only natural forces to do the job. And, as you might expect, the passive system is easier and less complicated (and therefore, less expensive).

There are two basic types of passive systems:

  • Batch: The batch system is as basic as you can get. The batch system is a water tank and a solar collector without any tubes or pumps. The water is warmed up, right inside the tank. That’s it! Gravity and natural convection move the hot water from the system into your pipes. (Science refresher: natural convection is when fluid particles naturally shift as the temperature rises.)
  • Thermosiphon: Don’t let the fancy name trip you up. In this system, the water tank is separate from the solar collector. Cold water moves through tubes in the solar collector. Then natural convection pumps the resulting hot water into the storage tank. From the storage tank, the water travels into the home’s water pipes. It’s only slightly different from the batch system.

Passive systems are usually used in warmer climates because there is plenty of sun to operate the system fully.

Active systems are used in colder climates and operate a little differently:

  • Direct: Water moves through the solar collectors and into a storage tank using electrical pumps and controls.
  • Indirect: Instead of directly heating water with the sun’s radiation, the solar collectors use a “heat transfer” fluid, such as antifreeze, to help warm the water. The antifreeze flows through sealed pipes into a heat exchanger, where it is surrounded by water. The water is warmed by the antifreeze, but does not mix with it. The water is then pumped into the storage tank.
  • Drainback: Similar to the indirect system, the drainback system also uses a heat transfer fluid. But instead of antifreeze, distilled water is typically used.  And true to its name, once the distilled water is used, it “drains back” into a separate tank to be used again.

Almost all of these systems work in conjunction with the electrical or natural gas water heater you’ve already got at home. While you’ll be able to use the solar water heater almost all of the time, the electrical or gas system can be switched on when demand for hot water is high or it’s too cold or dreary outside to power your solar system.

So Many Reasons To Go Solar

The best reason to go solar is the savings. You’re going to save money on your electric or natural gas bill immediately. Because hot water is the #2 energy “sucker” for most households, your bill will usually be cut in half. If you live in a colder climate, your savings may be less than if you lived in an extremely warm and sunny climate such as Florida or Arizona.

Solar water heaters are also environmentally friendly. You’ll be reducing the amount of carbon dioxide pollution into the environment. Not only will you be enjoying hot water, you’ll be reducing your carbon footprint at the same time.

Realtors report that by adding a solar water heater unit to your home, you increase its value. That could pay off in the long run, should you decide to ever sell your house.

Perhaps the most appealing factor, aside from the savings, is the ability to have hot water at any time, in any situation. When the power goes out, you won’t be left shivering in a cold shower. You can enjoy hot water anytime, as long as you’ve got the sun.

Return On Investment

The biggest drawback for homeowners wanting to switch to solar water heaters is, as you probably guessed, the price. A professionally installed solar water heater can cost $1000 and up. You can save money by installing it yourself… and you can even build your own. The most basic type, the batch heater, can be built as a DIY project. With some know-how and plenty of patience, you can build a batch water heater for less than $100.

And don’t forget, there are often federal and state incentives for installing solar and energy-efficient devices, which could make your purchase more affordable come tax time.

If you live in a sunny climate and use tons of hot water, you’re going to recoup your costs quickly. But if you live in colder climates and you regularly take five-minute showers, the return on investment will take a little longer. But one thing is for sure: the cost of electricity and natural gas will only continue to go up as time goes by. The sun is free… why not harness its power and become a little more self-reliant?

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