Solar water heaters: Are they worth the cost?

If you’re looking to reduce your electricity bills, a popular method to do so is installing a solar water heater. These systems can provide your home with hot water by utilizing a renewable resource instead of the electric grid.

We’ll give you the rundown on solar water heaters; how they work, popular brands, and most importantly – how much money you can save by installing one!

What is a solar water heater?

Unlike traditional water heaters, solar water heaters don’t use energy from the grid to heat water. Instead, these high-efficiency appliances use dedicated solar collectors on your rooftop to convert solar energy into heat. The heat collected is then used to warm the water in your home.

Solar water heaters have been extremely popular in the past because they cut down your electric bill and allow you to heat up your water with clean energy. The solar collectors directly heat your water and do not provide any other solar energy to your home; they convert solar energy into heat with up to 80% efficiency, significantly higher than the 20% typical for photovoltaic (PV) panels.

More recently, people have been opting for electric heat pump water heaters, which are coupled with home solar panel systems. Electric heat pumps cost an average of $6,000 and use grid energy to heat your water; however, when paired with a home solar system, they are able to still run on solar electricity. You can learn more about how heat pumps reduce energy consumption and work with solar panels.

If you aren’t able to install a full home solar system, or if you have an off-grid home, a standalone solar water heater can be a great option.

How do solar water heaters work?

Solar water heating systems are typically designed to provide 80-90% of the required hot water load to prevent overheating on peak solar days.

There are two main types of solar water heaters available for residential and commercial use: 

1. Active solar water heaters

2. Passive solar water heaters

Each of these works differently and consists of different equipment. 

Active solar water heaters 

Active solar water heaters use an electric pump to circulate fluid between collectors and the storage tank. These systems are generally more efficient (50-70% thermal efficiency) than passive systems, and while more common, they are also more complex and expensive. Active systems are suitable for all climates, especially colder ones with freeze protection like indirect circulation or drainback systems, and they are generally preferred in temperate climates like the Pacific Northwest and Mid-Atlantic due to occasional freezing and variable sun.

There are two different types of active solar water heaters:

• Active direct systems, where the water is heated directly in collectors and is then sent to your faucet and showerheads. The solar collectors are usually metal or glass tubes.

• Active indirect systems, in which a heat transfer fluid, like propylene glycol, is heated up within the solar collectors, and then transfers the heat to the water supply with a heat exchanger in a closed-loop system. Some heat loss occurs while the transfer fluid circulates the system. 

Passive solar water heaters 

Passive solar water heaters do not use circulating pumps to move hot water. Instead, they rely on natural convection as the circulation system, where hotter water rises to the surface and cold water sinks, in order to circulate water. Passive systems are less efficient (35-50% thermal efficiency) and carry a freeze risk unless equipped with drain down or seasonal shutdown capabilities.

Passive solar water systems are usually cheaper than active ones, as they don’t require special equipment to pump the water. They are also often DIY-friendly in mild climates due to simpler plumbing and no electrical components.

There are two main types of passive solar water heaters:

• Integral collector solar water heaters are large, black water storage tanks that are built into an isolated box with a top that lets sunlight through. The sunlight heats the water directly in the black tanks, which then flows into your plumbing system when you need hot water.

• Passive thermosyphon systems use metal flat plate collectors to heat small batches of water on your roof. When you open your hot water valves, hot water in the top of the batch collector flows down from your roof to your faucets. These usually are designed to contain 40 gallons of water. 

All solar water heating systems require a backup system, such as an electric or gas water heater, tankless water heater, or an indirect tank heated by a boiler.

What are the most popular brands of solar water heaters?

As solar technology continues to find new applications in our daily lives, more companies are manufacturing solar heaters. These are some of the most popular models on the market today.

• Duda Diesel manufactures machinery that uses biodiesel and other alternative fuels. They offer a range of solar water heaters for residential and commercial use.

• Sunbank Solar produces collectors, pumps, plates, and other components for solar water heating systems.

• SunEarth offers a range of solar energy solutions for homes and businesses, including solar water heating systems and elements.

• Apricus and Rheem are two of the more popular solar water heaters.

How much you spend on a solar hot water heater depends on what kind of system and what size system you get. 

Installed costs for residential solar water heaters in the US typically range from $2,500 to $9,000. For example, a passive batch system for warm climates, with basic storage and a flat collector, costs between $2,500-$4,500, while an active glycol system for cold climates, featuring a vacuum tube collector and a 150-gallon tank, costs between $7,000-$9,000. Larger active systems with evacuated tube collectors could potentially reach over $12,000.

How to select the right solar water heater

Each type of solar water heating system works best in different environments. Both passive and active solar water heating systems perform well in warm, non-freezing climates, with active systems achieving 60-70% savings on hot water needs. Direct circulation systems are ideal for climates where freezing is rare. For cold climates with freezing temperatures and less consistent sunlight, active systems with freeze protection (like indirect circulation systems using non-freezing fluid or drainback systems) are better suited. Evacuated tube collectors are more efficient in cold, cloudy climates due to superior heat retention, while flat-plate collectors are efficient and generally more cost-effective in moderate to warm conditions. You can find more specific details on solar water heater efficiency across US climates.

• Direct systems work best in areas that don’t often see temperatures below freezing. In cold climates, indirect active systems are more resistant to freezing damage.

• Want your solar heating system to do double duty? Invest in an indirect circulating system. The heating fluid can be redirected to heat your swimming pool or spa in between working to supply your home with heated water.

• Families that use more warm water during daylight hours benefit from integral passive systems. By producing multiple small batches of warmed water, family members won’t have to worry about having enough hot water for morning showers.

• Have more roof than ground space? A thermosyphon solar water heater fits on your roof, which leaves you more space in your living area.

• Integral collector storage systems can weigh over 400 pounds, so you have to make sure your roof can support the weight of a heavy water tank.  

You also have to consider how much sunlight your property receives, how much hot water you use on a daily basis, and your budget. The roof (or suitable unshaded land) for a solar water heater should receive direct sunlight between 10 AM and 4 PM year-round, ideally south-facing within 30° of due south. Even partial shade can reduce output by 20-40%. A good rule of thumb for collector tilt angle for year-round domestic hot water is latitude ±15°. A typical household uses about 64 gallons of hot water daily, but high-usage four-person households can exceed 80 gallons per day, requiring careful sizing; for a family of four using 60-80 gallons per day, plan for 40-80 sq ft of collector area and an 80-gallon tank.

When shopping for solar water heater options, look for ratings from the Solar Rating and Certification Corporation (SRCC). SRCC ratings allow you to easily compare different brands and models using expert third-party data. 

Every property is unique, so you should also seek expert guidance to ensure you choose the perfect system for your home. Finding a qualified contractor, ideally certified by the North American Board of Certified Energy Practitioners (NABCEP), is important for installation and annual maintenance inspections. Professional installation is highly recommended for the efficiency and longevity of solar water heaters.

How much money can you save with a solar water heater?

Solar water heaters generally have higher upfront costs than conventional systems, with installed residential costs typically ranging from $2,500 to $9,000. Water heating is the second largest energy expense in a typical US home, accounting for approximately 18-20% of total energy consumption, with an annual cost of around $600 for water heating as of March 2024.

However, after installation, a solar hot water system will slowly start to pay back its value in the form of lower utility bills. Solar water heaters can reduce water heating energy consumption by 50-80% depending on the climate zone, and annual savings for homeowners can range from $150 to $450.

Once you reach the end of your solar payback period (which varies significantly based on system cost, climate, and household hot water usage), your solar water heater will be producing nearly free hot water for the remaining lifetime of the system! Plus, because solar water heaters generally have few moving parts, they have relatively low maintenance costs, though regular maintenance is crucial for their longevity and effectiveness. A quality solar domestic water heater can offset 1.5-2.5 tons of CO₂ annually.

Keep in mind, depending on how much hot water you use, you might have to rely on a backup grid-tied hot water system. 

To calculate your potential savings, you’ll need to know:

• How much hot water your family needs on a daily basis.

• The cost of fueling your backup heater. Contact your local utility company for more information on energy costs for backup heaters.

• The SRRC or solar energy factor rating for your intended equipment. These numbers give you an idea of how efficiently your appliance will use gathered solar power.

• How much of your hot water use occurs during daylight hours. Using more hot water when there’s less sun available means more reliance on pricey grid energy.

• The life expectancy of your solar water heating system. The longer your heating system components last, the more money you’ll save.

With this information, you can determine the annual operating cost of your solar water heater. Compare this to your regular monthly utility spending to see how much energy savings you could get by switching to solar.

What rebates and incentives are available for solar water heaters?

Federal tax credits, state rebates, and utility programs can significantly reduce the net cost of solar water heaters. The federal residential solar tax credit has expired, but you can explore current state and local incentives, rebates, and programs by visiting our updated guide to solar incentives.

Your local utility company may still offer special discounts or rebates for the installation of qualified equipment. For example, Hawaii Energy offered rebates of $750 to customers who installed a solar water heater.

Find a solar water heater installer in your area to lower your utility costs without sacrificing comfort.

Should I get a solar water heater or a home solar panel system?

Solar water heaters were a popular option until a few years ago. The current trend is for homeowners to just get a solar panel system installed instead.

Why? Because the cost of solar panels has fallen so much in recent years. The most cost-effective option is to pair a residential solar panel system with an electric water heater. The solar panel system will not only cover your hot water costs but the energy costs of your whole home. Plus, electric water heaters are more efficient than even the highest quality solar water heaters.

Of course, solar water heaters can be worthwhile in some cases. They are more effective than solar panels at their specific function - heating water. The sunlight only has to heat the water, not get turned into electricity that then powers a system to heat the water. 

Solar water heaters also require much less roof space than a full solar system. A typical residential solar water heating system with a 350-liter storage capacity may require about 9 square feet of roof space and 7 feet of vertical clearance, with a two-panel system requiring about 9'x9' of roof area. If you have major space constraints, solar hot water heaters could be the best way for you to take advantage of solar energy.

Local solar companies will have the ability to install both solar panel systems and solar water heaters. They’ll also be able to determine what would be best for you - getting just one or both. For more information, including how much a solar energy system would cost for your home, contact a vetted local solar energy installer in your area.

Sources:

1. Selecting Your Solar Water-Heating System (ases.org)

2. Guide to Solar Water Heater Installation Best Practices (blog.heatspring.com)

3. Solar Thermal Flat Plate VS. Evacuated Tube Collectors? (blog.heatspring.com)

4. Different Solar Water Heating System Types (browardsolar.com)

5. Solar Hot Water Heaters Guide: Benefits, Costs and Installation (epb.com)

6. Try A Solar Water Heater (greenamerica.org)

7. 5 Key Factors To Consider Before Installing A Solar Water Heater (hindustanenergy.com)

8. Solar Water Heating Systems Cost in the USA and Canada — A Complete Guide by Hydro Solar (hydrosolar.ca)

9. Things to Consider While Buying Solar Water Heaters (neoappliances.com)