Question

I’ve heard solar water heaters are expensive and easily damaged by winter freezes. Is this true?

Asked by Aliya Rodriguez, Olympia Fields, IL

Is a solar hot-water heater expensive to put in your home? I think I want to get one, but I'm afraid to put one in. I've heard that the system parts freeze in the winter and are expensive to replace.

Answer

Cameron Habel

Answered by Cameron Habel

Oakland, CA

Cameron C. Habel Construction, Inc.

June 18, 2009

A solar hot-water system is a very efficient way to utilize the sun's energy. Compared to other water-heating methods, it provides the most energy for dollar spent.

A solar thermal system consists of:

  • solar collector panels on the roof,
  • a separate storage tank (or your water-heater itself can serve as the storage tank), and
  • pipes to distribute the hot water.
  • In Illinois, the system might also include a heat exchanger and pump. The heat exchanger will slightly reduce the system's efficiency.

If you install a certified system, it will qualify for rebates and federal tax incentives that will make the system more affordable. The Illinois Department of Commerce and Economic Opportunity sponsors the Solar Rebate Program, which is expected to resume funding in July 2009. The Illinois rebate will reimburse you as much as 30 percent of the installed cost (with a maximum rebate of $10,000). Federal tax credits will also offset as much as 30 percent of the installed costs (with no cap on the amount of the credits). The credits may be carried over in subsequent years. Illinois also offers a property tax incentive so that you will not be taxed on the increased value added to your property by the solar system.

Initial costs vary widely depending on which kind of system is installed and on the size of the system. That said, based on cost tables provided by the ACEEE (American Council for an Energy-Efficient Economy) consumer guide, the installed cost for a typical system with electric backup might be $4,800. With rebates and tax credits the net cost might be $1,920.

If your water-heating costs are cut in half, you might save $175 per year, depending on whether you currently heat your water with gas, oil, or electricity. Not including maintenance costs or cost increases for energy, the system would pay for itself in about 11 years. After the payback period, you accrue savings over the life of the system, which is anywhere from 15 to 40 years. Paybacks vary widely. Generally, payback periods are shorter in areas with higher energy costs, areas with a greater number of sunny days, and areas that do not experience winter freezes.

To address the second part of your question, a properly designed and installed system will not freeze. In places like Illinois that are subject to prolonged freezes, an "indirect" or "closed-loop" system is often installed. This system makes use of a type of antifreeze that is heated by the sun. A heat exchanger transfers the heat in the antifreeze to the water system for use in your home. The antifreeze protects the solar heating system from freezing.

"Direct systems," which don't use antifreeze, use flush-type valves to protect the system from freeze damage. Before the water approaches the freezing point, the flush valve opens, purging the water from the system. Other system designs use a pump to circulate warm water from the storage tank to prevent the system from freezing. Solar thermal systems also utilize devices to prevent damage if the system gets too hot.

Solar thermal systems are certified by independent agencies and are given a thermal performance rating.

 

For more information:

The Midwest Renewable Energy Association is a good resource for information about renewable energy in the Midwest region.

The U.S. Department of Energy's website offers tips on how to estimate the annual operating cost of a solar thermal water-heating system.

Tagged In: solar water heater, energy tax credit

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.