The 4 Best Solar Water Heaters

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Solar water heater on roof


Hot water is essential if you don’t like cold showers or dirty dishes, but it’s also a significant source of total home energy usage. Solar water heaters harness the sun to heat water instead of relying solely on electric or gas—plus, it’s a way to sidestep total dependence on the grid. It’s also possible to use solar water heating for other uses which hog energy, such as heating a swimming pool. While they’re not widely in use in every region of the country, solar water heaters are more common in sunny climates such as the Southwest or Florida. But they also can be used in cold climates with proper design that prevents the system from freezing.

Solar water heaters include a solar collector and storage tank and typically are installed with a backup heating system so you’ll have hot water even on cloudy days or during times of high demand. You must ensure, however, that your intended site will provide adequate sun exposure with solar collectors situated on unshaded areas that face south. You’ll also need to consider landscape features, such as large trees, that shade the area daily or seasonally.  Because there’s no one-size-fits-all solution for every home, you’ll need to discuss your options with a qualified installer.

 Ahead, our top picks for solar water heaters:

Best Solar with Electric Backup: Alternate Energy Technologies

Indirect Systems

Courtesy of Alternate Energy Technologies

Founded in Florida in 1975, this company has been producing solar energy solutions for more than 45 years for both residential and commercial settings. If your home runs renewable energy, then a solar water heater with electric backup can be operated emissions-free.

Alternate Energy Technologies offers both direct and indirect solar water heater systems; direct systems typically are installed in the southern U.S. and tropical locations. They’re called direct because the sun’s heat is transferred through the collector directly to the usable waterline.

Indirect systems are for climates with freezing temperatures. They’re indirect because the sun heats fluid circulating in a closed loop that never comes in contact with the water, which is stored in an insulated tank. Both systems are ENERGY STAR certified and have a 10-year warranty on the collectors.

Best Solar with Natural Gas Backup: Rheem Featuring Gas Assist Heat Exchange Tank

Rheem Featuring Gas Assist Heat Exchange Tank

Courtesy of Tankless Online

The name is instantly recognized in the industry, and this active solar model has gas backup so that you’ll never worry about running out of hot water on rainy days. The system includes a single tank, collectors, controller, pump, glycol solution to prevent freezing, and thermal expansion tank for the glycol loop. It has a 75-gallon capacity and is certified by SRCC.

Although natural gas is a fossil fuel, this systems is suggested as a drop-in replacement if you currently have a gas water heating system and want to add some solar water heating without going fully electric. The product has a six year warranty and is manufactured in the United States. The company is dedicated to reducing greenhouse emissions by 50% and training 250,000 contractors in sustainable installation recycling best practices by 2025.

Best for Heating Pools: Eagle Sun Pool Solar Panels

Eagle Sun Pool Solar Panels

Courtesy of Alternate Energy Technologies

Heating a pool is expensive, but simple systems can solve that problem by using the sun’s energy—taking off the chill and extending your season in cold climates. The pool panels, which come in multiple sizes, are manufactured right here in the United States, and they’re also tested to withstand hurricane-force winds of up to 159 mph.

They’ve been approved by the Florida Solar Energy Center and the Solar Rating & Certification Cooperation (SRCC), and they come with a 10-year guarantee. The company also sells the additional system components needed for each panel.

Best Portable: Nemo Equipment Helio Portable Pressure Camp Shower

Nemo Equipment Helio Portable Pressure Camp Shower

Courtesy of Amazon

After a day on the trail, nothing feels better than a hot shower, but what if you’re camping off-grid? This small unit heats up in the sun while you’re hiking and it doesn’t have to be suspended from a tree, which isn’t always the easiest task.

Weighing just over a pound, this unit holds almost 3 gallons of water for a shower that lasts 5 minutes or more. The foot pump helps you keep it pressurized for a continuous spray, and the 7-foot hose is long enough for a multitude of clean up tasks from showering to rinsing off muddy dog paws.

What to Consider When Shopping for a Solar Water Heater

Type of System

While the designs solar water heating systems vary, they all include a solar collector and storage tank. They’re usually described by the type of collector and circulation system used. For example, the most common types of collectors include:

  • Batch collectors, or Integrated Collector Storage (ICS) systems, which heat water in dark-colored tanks, storing it there until water is drawn. This type isn’t recommended for cold climates.
  • Flat-plate collectors, which consists of a metal enclosure, an absorber plate and flow tubes. The absorber transfers the sun’s energy to the water flowing through the tubes attached to the absorber.  
  • Evacuated tube collectors, which consist of a glass or metal tube containing the water surrounded by a larger glass tube, creating a vacuum so little heat is lost. These are the most efficient systems and can operate in temperatures as low as -40 degrees.

The circulation system may be direct, indirect, active, or passive. A direct system circulates water through the solar collectors where it’s used directly or stored in a tank until called for. An indirect or closed system uses a non-freezing liquid to transfer heat from the sun to the water in the storage tank, transferring heat to the water as it passes through a heat exchanger. An active system uses electric pumps and controllers to move water from the collectors to the storage tanks. Finally, passive systems require no pumps, moving water by natural convection from collectors to the storage tank. 


Your contractor will help you figure out what you need, but generally, stick with 20 square feet of collector area for a family of two. Add 8 square feet for every additional person if you live in the south, or 12-14 square feet in the north. A small storage tank (50 to 60 gallons) is recommended for one to three people, medium (80 gallons) for three to four people. The size of the tank also increases with the size of the collector for active systems in warm climates to prevent overheating when water demand is low.

Freeze Protection

Even in warm climates where it seldom freezes, such as south Florida, it’s recommended to install freeze protection because a single freeze can destroy a collector. Various methods exist, including flush-type valves which purge water from the system when freezing temperatures occur; water recirculation; draindown systems; and antifreeze systems.  


Water heaters are the second biggest energy user in the home; those that are certified by ENERGY STAR have been evaluated for reliability and efficiency. Also, only complete systems with backup heating are qualified.

In addition, systems also may be certified by the Solar Rating & Certification Corporation (ICC-SRCC), a third-party certification organization for solar thermal products regarding safety, durability, and performance standards.

Frequently Asked Questions
  • Do solar water heaters work in winter?

    Yes, but you’ll need a backup system, which you must rely on more often in winter when sunlight is sparse.

  • Do I have to change my habits with a solar water heater?

    Maybe. To maximize the use of solar energy, it’s best to use the most hot water later in the day when the system is operating at its peak. Also, if you usually do multiple loads of laundry each day, you may want to spread it out so that you’re doing fewer loads per day to reduce the amount of backup energy required.

  • Can solar water heaters save you money?

    You’ll have to take into account the cost of installation, which varies depending on the type of system you install and where you live. Residential units cost around $9,000, not including federal tax credits and some state incentives available for residential installations (though not for solar pool heaters).

    Also, how much you’ll save in the long run depends on several factors including how much water you use, storage tank size, and price of fuel for backup water heating. But because heating water accounts for 18% of total home usage, the EPA estimates that you could cut your energy costs by at least 50% of the hot water portion of your bill. Calculators like the one developed by Florida Solar Research Center at the University of Central Florida also can help you determine potential cost savings.

  • Should I get a backup system for my solar water heater?

    In a word, yes! Unless you don’t mind chilly showers or live somewhere with a warm climate year-round, it’s still smart to get a backup that’s run by electric, gas, or propane, depending on your region’s availability.

Why Trust Treehugger?

Treehugger is dedicated to educating readers about the benefits of renewable energy systems. Arricca SanSone specializes in writing about home, shelter, and gardening. She researched the market based on data from the EPA, Department of Energy, ENERGY STAR, and the Florida Solar Research Center.

View Article Sources
  1. Energy Cost Calculator for Electric and Gas Water Heaters.Office of Energy Efficiency & Renewable Energy.

  2. Sizing a New Water Heater.U.S. Department of Energy.

  3. Save Money and More with Energy Star Qualified Solar Water Heaters.ENERGY STAR.

  4. For Homes - Q&A.” University of Central Florida.

  5. How Much Does Solar Hot Water Cost?EnergySage.

  6. Renewable Hot Water Heating.Environmental Protection Agency.

  7. RHC for Single-Family Homes. Environmental Protection Agency.