Solar Water Heaters


Using sunshine to heat or preheat your water can cut your annual hot water costs in half. An ENERGY STAR certified solar water heating system can cut your annual hot water costs in half, and is generally designed for use with an electric or gas back-up water heater.

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What else should I look for when buying a solar water heater? 

If you are interested in an ENERGY STAR qualified solar water heater for your home, consider the following before you buy.

  1. Determine if your site is suitable. Most solar water heating systems are installed on the roof. For best results, your roof should:
    • Receive direct sunlight between the hours of 10 AM and 4 PM year round;
    • Face South (within 30° of due south, not magnetic south); and
    • Be sturdy with the shingles in good condition.
      • If your roof isn't appropriate for a solar water heater, but you have suitable unshaded land next to your home, you may want to consider a ground-mounted system instead.
  2. Decide what type of system meets your needs and lifestyle. A solar water heater contractor will help you determine what type and size system best suits your needs. Take the following steps so you can have informed discussions with contractors during the purchasing process:
    • Review your roof warranty, if you have one, to determine if and/or how installing a solar panel can affect this warranty. Make sure the contract requires the contractor to repair any leaks or damage to the roof during installation or operation caused by their work.
    • Understand how solar water heaters work so you can discuss which collector type and circulation system makes the most sense for you.
    • Protect against freezing in colder climates. Some solar systems are appropriate for freezing climates, while others are not. As a general rule, if there is a good chance that temperatures will fall below 42°F, choose either a closed-loop system with antifreeze as the heat transfer fluid, or a system that automatically drains back when temperatures fall too low for comfort. Steer clear of batch systems if you live in a climate with distinct winters.
    • Estimate the capacity you'll need. Use the gallon capacity of your current water heater as a starting point. You can find your current water heater's capacity or volume on its nameplate or yellow Energy Guide sticker. This should help you discuss the sizing of your solar system with contractors. If you have recently added or are planning to add more occupants to your household or a new shower, faucet, dishwasher or washer that will be in frequent use, take that into account in your discussions
  3. Plan ahead if you can. To make your life easier, plan ahead for your next water heater replacement and you will have time to research and select the best technology for your situation before it's an emergency. Your installer may need time to order the proper model, and it may take longer to install than a standard water heater.
  4. Check product availability. Find out what certified models are available on the market by viewing the ENERGY STAR Product List. You will then need to visit manufacturer Web sites, call local installers, or visit your local retailer to determine who carries these units in your area, or call your plumber or contractor to see what products are available.
  5. Contact a Solar Contractor or Manufacturer. Installing a solar water heater on an existing home requires careful installation, which often includes running pipes through walls. You will want to find a local contractor who can assess your site, provide recommendations, install a system, and then perform periodic maintenance. Use a contractor certified by the North American Board of Certified Energy Practitioners (NABCEP) if possible.
  6. Search for rebates. You may be able to reduce your costs by taking advantage of rebates. Be sure to review the eligibility rules before you make your purchase.
  7. Don't forget about maintenance. For a solar thermal system, don't forget about maintenance. After installing a solar system, it is important to perform periodic maintenance to ensure efficient operation. In addition to hiring a qualified contractor for annual maintenance inspections, you should periodically check the following:
    • On the roof or ground, depending on installation:
      • Collector is clean and not shaded.
      • Collector is sound, sealing and glazing are not cracked or yellowing.
      • Fasteners connecting collector to roof are sound.
      • Piping and wiring are well-connected, well-insulated, and without damage.
      • Roof penetrations are well-sealed.
    • In the home:
      • Pressure relief valve is not stuck completely open or closed.
      • Pumps (in active systems) activate when the sun is shining.
      • Pipes are free of mineral build-up.
      • If you live in an area with hard water, you may need to add de-scaling agents to the water every few years. For example, you can run a vinegar solution through the collector or hot water loop every three to five years.
  8. Consider other measures that may also save energy. If you are in the midst of new construction or home remodeling project, you may have come across other proposed approaches to water heating. Under the right circumstances, these technologies can save significant amounts of energy.
    Point-of-Use (POU) Electric
    Hot Water Recirculating System

Be sure to look for the ENERGY STAR when shopping for a solar water heater

Current Specification Effective Date: April 16, 2015

The specification covers high-efficiency gas storage, whole-home gas tankless, solar, and high efficiency electric storage water heaters. Products must meet minimum requirements for energy efficiency, hot water delivery, warranty period, and safety.

Water Heater Key Product Criteria: ENERGY STAR

Learn How a Product Earns the Label

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