5 Best Solar Water Heaters [2021 Guide]

solar-water-heater

5 Best Solar Water Heaters [2021 Guide]

Every homeowner could do with the best solar water heater systems. They can bring down your monthly water heating bills and help you save the environment. These systems also don’t need expensive solar panels and are easy to install as well.

Still, while the benefits of solar water heaters are obvious, what might not be as apparent is the system that could meet your requirements. That’s because these water heating systems come in various sizes, from compact, one-fixture models to those that can heat your pool.

In this article, we’ll review the five best solar water heaters currently on the market. We’ve also included a buying guide to assist you in the purchasing process. Whatever your requirements and budget, you’ll get a solar water heater system that is the perfect fit for you.

In a Hurry? Here are Our Top Three Picks

Is Solar Water Heater Right For You?

Your house’s design and location will determine whether a solar water heater is right for you. They will decide how easily you can install a solar water heating system, and how well the solar water heating system will perform.

Solar water heaters (SVH) work best if you’ve a section of roof that:

  • Faces true north or close to true north (the direction that points towards the North Pole). In the United States, true north varies from +18* in Washington state to -19* in Maine. SWH whose collectors face west or east suffer a 20% loss in annual performance.
  • Receives good exposure to the sun year-round (ideally with zero shade throughout the day – and keep in mind that shading will increase in winter)
  • Is large enough to house the collector(s) (roughly 1 square meter per person in your house)
  • Isn’t located too far from the hot water tank. The greater the distance between the collector(s) and the tank, the lower your SVH’s efficiency will be. 

Selection Criteria: How We Chose the Best Solar Water Heaters

Here’s the criteria we used for their selection:

  • Stainless steel construction: Stainless steel can resist rust and corrosion, two of the biggest nemesis of water heaters, much better and for much longer. That is why most models you’d see below have stainless steel piping.
  • Multiple safety systems: Are solar water heaters safer than their electric or gas counterparts? They are. Are they 100% safe? The jury is out. Which is why 4 out of the five models we have picked for you come with at least 2 safety systems.
  • Considerable capacity: The required capacity of the solar water heater you need depends on the size of your household. Check out our buying guide section to know more about this.

Duda Solar Split System

Duda Solar Split System
  • 20 Duda Solar Vacuum Tubes, Stainless Steel Water Tank, Working Station...
  • Automatic Air Vent, Submersible Water Pump (for system charging),...
  • 2 Gallons of Food Grade Inhibited Propylene Glycol
  • Requires: Plumbing from tank to collector, speaker wire for sensors, other...
  • OG-100 SRCC Collector Certified, Eligible for 30% Federal Tax Rebate

The DUDA Solar Active Split System is our top pick for many reasons. Firstly, it comes from a reputable brand. Duda is SRCC-certified and you can use it for state or federal tax credits and exemptions, an excellent incentive for on-the-fence homeowners to opt for a solar heating system.

How It Works?

The Duda Solar 200L uses the sun’s thermal energy to heat a non-freezing fluid in its collector. A pump then sends the heated fluid to the storage tank, where it transfers its heat to the water, without the fluid or water mixing together. One benefit of this approach is that you can store the tank anywhere.

This means you can place the tank in the basement (or anywhere else where your pipes are), the collectors on the roof and there still won’t be any heat losses. This, in turn, means that hot water won’t take long to flow from the tank to the tap.

Features

This solar water heater itself has multiple exceptional features. It comes with a solar water heater collector and a food-grade stainless steel storage tank. Duda has also included two gallons of food-grade inhibited propylene glycol (an antifreeze solution) in this solar water heater’s package

The collector comes fitted with twenty 14mm solar tubes. Thanks to the 45-degree stand (also included), you can easily position the tubes for maximum sun exposure. However, if you’re planning on mounting the tubes elsewhere, Duda lets you exchange the stand with a slope or 37-degree roof stand.

Safety Systems

Multiple safety systems are also on offer. A solar water heater working station connects the collectors, sensors, storage tanks and relays to regulate the split pressurized system. The working station uses a pressure relief gauge, check valve, and pressure relief valve to achieve its objective.

An automatic air vent purges air from the top of this solar heater to prevent excessive build-up of pressure, and an 8-liter expansion tank would protect the system if your hot water demand is less than the amount of solar energy being produced. A thermostatic valve, meanwhile, prevents scalding.

Pros

  • 200-liter (53 gallons) capacity
  • Comes with an anti-freeze solution
  • Has food-grade stainless steel storage tank
  • Thermostatic valve prevents scalding

Cons

  • Expansion tank’s capacity could have been bigger

How It Compares With Our Criteria

  1. Stainless steel construction: Yes
  2. Multiple safety systems: Yes
  3. Considerable capacity: Yes

Sunbank Solar Water Heater

Sunbank Solar Water Heater
2 Reviews
Sunbank Solar Water Heater
  • 10 year Collector Warranty
  • No Pumps - No Moving Parts - No Glycol
  • Easy Installation for DIY or plumber. Is affordable, reliable, and pays for...
  • High Density Polyurethane Insulation provides excellent heat retention. If...
  • Ships to the U.S. and Hawaii - contact us for shipping information

There are various similarities between the Sunbank and Duda Solar water heaters. Both come from respected brands. Both allow you to claim federal or state tax rebates on their purchases. And both are SRCC certified. That’s where the similarities end.

How It Works?

Unlike the Duda 200L, the Sunbank solar water heater works passively. It uses evacuated solar tube collectors (which absorb up to 96% of solar radiation that hits them) to convert solar energy into heat, before transferring the heat to the water in a super-insulated tank.

This portable solar water heater doesn’t come with any pump, which means it relies on well or municipal pressure to move hot water out of the tank and cold water into the tank. This approach is the reason why this heater lacks any moving parts, making it virtually maintenance-free.

Features

The Sunbank Solar water heater is available in two versions. Go for the 80-gallon model if you have a large household, as the 40-gallon model will serve only 1 – 3 people. Both the heaters have high-density polyurethane insulation to prevent heat loss and ensure energy savings.

80 Gallon Solar Water Heater
  • 10 Year Collector Warranty - No Pumps - No Moving Parts - No Glycol
  • SRCC Certified. The only collector of its type to be certified and eligible...
  • Easy Installation for DIY or plumber. Is affordable, reliable, and pays for...
  • High Density Polyurethane Insulation provides excellent heat retention. If...
  • Ships to the U.S. and Hawaii - contact us for shipping information
40 Gallon Solar Water Heater
2 Reviews
40 Gallon Solar Water Heater
  • 10 year Collector Warranty
  • No Pumps - No Moving Parts - No Glycol
  • Easy Installation for DIY or plumber. Is affordable, reliable, and pays for...
  • High Density Polyurethane Insulation provides excellent heat retention. If...
  • Ships to the U.S. and Hawaii - contact us for shipping information

They also have a 10-year warranty on the collectors and a 1-year warranty on the remaining parts. A 316-grade stainless steel storage tank, which resists corrosion better than its 304-grade counterpart, is also on offer. Plus, you also get a highly corrosion-resistant stainless steel and aluminum bracket.

Safety Systems

This system has a temperature and pressure relief valve to prevent overheating. Upon sensing that the water temperature has risen above the preset temperature, the valve would release hot water, bringing down the system’s internal temperature.

However, you cannot use this model in sub-zero temperatures as it doesn’t come with any active (re-circulation pump) or passive (freeze protection valve) freeze protection. This makes the Sunbank ideal for areas that receive an adequate amount of sunlight year-round. 

Pros

  • Incredibly easy to maintain
  • Easy to install, even for novice plumbers
  • Comes with a 10-year warranty

Cons

  • Can’t be used in sub-zero temperatures

How It Compares With Our Criteria

  1. Stainless steel construction: Yes
  2. Multiple safety systems: Yes
  3. Considerable capacity: Yes

Sportneer Solar Shower Bag

Sportneer Solar Shower Bag
859 Reviews
Sportneer Solar Shower Bag

  • PORTABLE SOLAR SHOWER: Camping is great fun but don’t you just want to take a shower sometimes? No need to check into a hotel just to get clean—a rinse-off is just moments away with this solar-powered camping shower bag!
  • PREMIUM MATERIAL & BEST HEATING CAPACITY: Built tough to last through endless outdoor trips and travel, this camping shower bag is made of the right stuff.
  • LARGE WATER CAPACITY: Holding a capacity of 5 gallons (20 liters), it’s more than enough for several showers.
  • UPGRADED VERSION: In this improved and upgraded version, it has a better hose, shower head and water tap.

The Sportneer Solar Shower Bag is different from the two solar water heating systems we saw above. Its capacity – a meager 5 gallons – makes it unsuitable for meeting the hot water demands of an entire household. The best this solar water heater could do is power a single shower.

How It Works?

This solar power water heating system relies on gravity to do its bidding. Wash the bag with 1 spoonful of hot soda upon arrival, fill it with water and place it in the sun. Wait for 3 hours as the manufacturer claims it can raise water temperature by up to 30* within three hours.

Afterward, hang it by a tree (or any other object that is above your height) and open the shower valve’s cap to enjoy sizzling water. Sure, there’s nothing high-end about how this model works, but the alternative – going for days without a bath for want of cold water – makes it a worthwhile option.

Features

This solar shower bag comes with a storage basket to hold your toiletries. Its transparent design means you’d never be in the dark about its water level. A non-slip handle makes it easy to carry, and the water inlet has a sealed cup to prevent water leakage.

Then there is the shower head. It’s equipped with a convenient open/close switch to let you control water’s flow rate. The longer hose means you can count on the shower head to reach all your body parts, and thanks to the Velcro straps, don’t have to worry about it coming off.

Safety Systems

A temperature indicator allows you to stay abreast about the water temperature and minimize the likelihood of burn injury. However, since the indicator is back-facing, you’d have to turn the bag around (or over) to come face to face with it.

Pros

  • Durable PVC construction
  • Has a temperature indicator
  • Heats water by about 30*C in 3 hours
  • Front pocket for toiletries

Cons

  • One user complained about water leaking from the screw cap

How It Compares With Our Criteria

  1. Stainless steel construction: Not applicable
  2. Multiple safety systems: Yes
  3. Considerable capacity: Yes

SunHeater Solar Pool Heater

SunHeater Solar Pool Heater
735 Reviews
SunHeater Solar Pool Heater
  • Simple DIY installation; for in ground or above ground pools
  • Installs on roof, rack, ground or fence
  • Patented web design for maximum exposure to sun's rays
  • Uses existing pool pump
  • Raises pool water temperature 6-10 degrees F

The SunHeater Pool Heater is rated for up to 18’ round pools. It’s an active solar water heater that connects to an existing pool pump to provide you with hot water. Provided you have a bigger pool than what it can adequately fill, you can connect two of these pool heaters.

How It Works?

The SunHeater S120U’s working principle is quite simple. It comes with durable polypropylene panels/collectors that can increase water temperature by as much as 15*F. Water from your pool will be pumped through these solar panels by your pool pump.

The panels will then increase water temperature, before the heated water is returned to your pool through the return lines. It will be replaced in the collector with cold water, and the whole cycle will continue until your entire pool water is at the same temperature.

Features

Most other solar pool heaters can only be mounted on your roof. This forces you to install long pipes that could deliver water from and back to the pool. The SunHeater S120U is different. You can mount this model anywhere you get at least half-a-dozen hours of dull sun during the day.

That doesn’t mean it won’t require additional kits or plumbing. Both might be needed. However, by reducing the distance between the pool and the collectors, it will save you money on long length pipes. This also makes the S120U relatively easy to install. 

Safety Systems

The SunHeater S120U comes with no safety features whatsoever. Make sure to mount it at a place which is away from children, elderly and the pets. The panels tend to get hot and you may not want anyone to touch it for the fear of a burn injury.

Pros

  • Simple DIY installation
  • Uses existing pool pump
  • Can be installed on roof, ground, rack, or fence
  • Covered with a 4-year (limited) warranty

Cons

  • Some users have voiced complaints about the quality of materials used

How It Compares With Our Criteria

  1. Stainless steel construction: Yes
  2. Multiple safety systems: No
  3. Considerable capacity: Yes

Northern Lights Group Solar Hot Water Heating Package

Northern Lights Group Solar Hot Water Heating Package
  • SWH-1 Solar Hot Water Heating Package - DIY Solar Kits
  • Complete solar heating package for domestic hot water for up to 4 people
  • Simple to install with no soldering or electrical wiring required
  • All kits come standard with RESOL DeltaSol Bs+ controller two relays for...
  • Requires SIN or Tax ID for shipping to USA

The Northern Lights Ground Solar package has it all. Apart from offering an above average capacity (50 gallons), it comes with every screw and every bolt needed for DIY installation. Not only that, but the way this solar water heater works also saves you money.

How It Works?

The Northern Lights SHW1 is an active (indirect) solar water heater. It uses a non-freezing liquid to heat water. The sun’s thermal energy, after being converted into heat by its solar collectors, heats the non-freezing fluid inside, which is then pumped to the hot water storage tank.

Once there, the fluid transfers its heat to the water without coming into contact with it. This results in the liquid’s temperature coming down, at which time it’s pumped back to the collector to get reheated. This approach is the reason why the heater will always ensure you’ve access to hot water.

Features

One of this solar water heater’s highlights is that its controller allows it to heat two separate zones. This means it can provide heat to a swimming pool while also heating your hot water tank for showers, faucets, and other water appliances.

This model also comes with a 4.5Kw back-up electric heating element, which will kick into gear when the weather fails you, ensuring you always get hot water. Plus, it’s easy to install with no soldering required and comes with all the components you need for its installation.

Safety Systems

This heater comes with two safety systems. It has an expansion tank that would protect the system if your hot water demand is less than the amount of solar energy being produced. The tank would do that by letting in excess water from the heater, reducing the whole system’s pressure.

However, chances are that matter won’t come to such a head where the expansion tank will have to come into play. Why? Because of this model’s air vent which will open up to let excess pressure out, keeping the risk of bursting at a minimum.

Pros

  • Offers two-zone heating
  • Comes with an expansion tank
  • Has all the components you need for installation
  • Back-up electric heating element should weather fails you

Cons

  • Astronomically expensive

How It Compares With Our Criteria

  1. Stainless steel construction: Yes
  2. Multiple safety systems: Yes
  3. Considerable capacity: Yes

What is Solar Water Heater?

Solar water heaters use the sun’s thermal energy to heat water. They come with two parts: solar collectors (that capture the sun’s energy) and storage tanks. Some solar water heaters also have sensors and valves to streamline their performance and efficiency.

How Does a Solar Water Heater Work?

Solar water heaters work by capturing energy from the sun in the solar collector panels. The panels are located on the part of your roof which receives the most sunlight across the day. After collecting the solar energy, the panels transfer it to the water kept in a hot water tank, raising its temperature.

Types of Solar Water Heaters

Based on how they circulate hot water, there are different types of solar water heaters.

Active solar water heaters

Active solar water heaters use the sun’s thermal energy to heat water in the solar collector. They then use internal pumps and sensors to transfer hot water from the collector to the storage tank. These water heating systems are used primarily for domestic water heating.

Passive solar water systems

Passive solar water systems don’t use internal pumps or sensors to circulate hot and cold fluids. Instead, they rely on the laws of physics. This means that after heating water, they allow hot water to rise naturally to the top of the reservoir. These water heating systems are ideal for mild climates.

Direct systems

Direct solar water heaters let you use the heated water directly, store it in the tank, or send it to the tankless water heater. These systems are recommended to be used in areas where the temperature rarely falls below freezing point. That’s because they don’t have freeze protection to operate in frigid climates.

Indirect or closed-loop systems

Indirect systems use a non-freezing liquid to heat water and are ideal for freezing climates. The sun’s thermal energy heats the non-freezing liquid in the solar collector. From there, the fluid goes into the heat exchanger in the storage tank, where it transfers its heat to the water, before returning to the collector.

How Do I Choose a Solar Water Heater?

Solar water heating systems are available in various sizes. Some supply hot water that is just about enough for a single shower. Other solar hot water systems, which come with multiple collectors, can heat an entire pool. Here’s how you can choose a solar water heating system for your home:

Size

The size of your solar water heating system depends on your hot water requirements. This, in turn, depends on the number of people in your home. The higher the number of people in your household, the larger the collector panels’ area and storage tank size need to be.

Here’s how you can size your solar hot water system:

Open Loop vs Closed Loop

Open-loop systems circulate water through the collector panels, heat it directly and return it to the hot water tank. They cost less than their closed-loop counterparts and deliver better performance as a collector is directly heating the water.

However, these systems aren’t ideal for low water quality areas. Their performance might also reduce over time if sediments or other impurities build up on their pipes. Lastly, these units don’t come with any frost protection measures.

Pros of open-loop systems

  • Affordably priced
  • Deliver excellent performance
  • Are relatively easy to install

Cons of open-loop systems

  • Aren’t ideal for low water quality areas (susceptible to sediment build-up)
  • Don’t come with any frost protection measures

Closed-loop systems don’t tolerate any mixing between the heat transfer fluid and the water being heated. This makes them highly suitable for low water quality areas. Provided you can keep them well-maintained, closed-loop systems can last for decades.

On the flip side, since these units use glycol as frost protection, you’d have to replace the glycol periodically if you’re living in a frigid climate. This increases their running costs. And keep in mind that closed-loop systems cost more upfront, too.

Pros of closed-loop systems

  • Can last for decades
  • Suitable for low water quality areas
  • Ideal for frigid climates

Cons of open-loop systems

  • Higher running costs

Hot Water Tank

Some solar water heating systems come with a tank. They tend to be pricey. The majority allows you to purchase a tank separately to keep the upfront cost affordable. Here’s what you need to consider when shopping for a hot water tank for your solar water heating system:

  • Conventional hot water tank. It has a heating element, lets cold water in from the bottom and flushes out hot water from the top. However, it lacks a thermostat and has a design that prevents it from making the most of solar energy.
  • Specialist solar water heating tank. It stores more water and lasts longer than a conventional hot water tank. It also has thermostat connections and is specially designed to make the most of solar energy.

Thinking of retrofitting the solar water heating setup to your existing hot water tank? Then there are some things you might want to know about, including:

  • Experts recommend against retrofitting a solar water heating system to a tank that’s less than A grade – the losses of the tank will jeopardize the solar heating system’s performance. To counter this, you’d have to install a cylinder wrap, increasing the installation cost.
  • Conventional hot water tanks can usually hold 180 liters or less. This storage capacity is nowhere near enough for a solar water heating system to deliver optimal performance and meet the hot water needs of a household of three or more people.

Pro Tip: If your solar water heater comes with a hot water tank, don’t forget to check the material the tank is made of. If the tank is constructed of enamel, make sure to ask the manufacturer if they warrant the tank for use with a solar water heater.

Controller

A controller is needed on active solar water heating systems. It’s responsible for turning the pump on when the collector has generated sufficient heat, and off when it hasn’t done so. An extra function of the controller is to regulate the use of ‘booster’ electric or gas heating systems.

All in all, a high-end and well-installed controller will enable you to get the best performance out of your solar water heating system. Make sure you talk to the heating system’s supplier or installer to know more about the type of controller that is ideal for you.

Frost Protection

Do you live in a frost-prone area? Make sure that your heater comes with some sort of frost protection. Otherwise, when the inevitable happens and frost starts falling, the heat transfer fluid or water inside the collector panels would freeze, doing costly damage to the panels.

Different solar water heating systems use different types of frost protection. For instance, some closed-loop systems use a water/glycol mixture to minimize the risk of freezing. There’s nothing wrong with this except that glycol would need regular replacement, increasing the heating system’s running cost.

Some open-loop systems turn the water on when the collector panels start to freeze. The flow of hot water between the tank and collector panel will prevent freezing but at the cost of energy savings. Also, if there’s a power outage, the frost might do costly damage to the panel.

Solar Water Heater Installation

Installing a solar water heater isn’t everyone’s cup of tea. Many variables are involved in the whole installation process, making the entire process extremely complicated. That’s why we suggest those of you who aren’t expert plumbers leave the installation to one.

For others, follow these steps to install a closed-loop solar water heater:

Step 1: Mount the solar collector(s) on the roof

To properly mount them, remove parts of your roof shingling and expose the flat tar paper that protects the shingles from the roof deck. Next maneuver the collectors in place and screw them into the roof deck and the rafters lying underneath.

Step 2: Install the heat exchanger and storage tank(s)

Follow the instructions given in your solar water heater’s manual. Additionally, you might want to make room for both these pieces of equipment in your utility closet or basement, as that’s where they’re easily accessible by antifreeze tubing and water lines.

Step 3: Install the piping for the antifreeze fluid

Antifreeze piping runs between the heat exchanger and the hot water tank. Installing it will require you cut a couple of holes in your roof deck – one for the pipe that sends antifreeze to the collectors, and one that brings it back. Make sure the holes’ diameter is equal to that of the pipe.

Step 4: Install water transport pipes

Water transport lines will take water from the storage tank to the rest of your home. Most homes will already have them, so the only thing you’d have to do is to delink the water connection from your existing/old hot water setup and connect it to the new storage tank.

Step 5: Install control systems

You need to install two sensors along your solar hot water system. One sensor should be connected to the base of the storage tank, and one to the collectors. Both will guide the central control system on when to start circulating antifreeze fluid.

This means you also need to install a central control system and connect it to your household’s electricity supply. Take special care while installing this device as it will be the “brains” of your solar powered water heater, facilitating injection of antifreeze after receiving data from the temperature sensors.

Final Step: Insulate the heating system

The last step involves insulating each part of your solar power water heater. This will require plugging holes in your roof, insulating piping, and making sure that the connections between components are fully sealed. Inadequate insulation might lead to energy loss which would translate into lost savings.

So it’s imperative that you insulate the system properly.

Solar Water Heater Maintenance Checklist

Solar water heaters do not require much maintenance. However, it would be good to inspect your system every once in a while to extend its shelf life. With this in mind, let’s look at the solar water heater maintenance checklist we have prepared for users:

  1. Regularly check for any leakages in the pipes, panels, tanks, etc.
  2. Inspect wires for loose connections and ensure there’s no dust on the solar water heating panels.
  3. Make sure that the pipe insulation and frost protection are intact.
  4. Examine mounting connectors for tightness.
  5. Inspect plumbing for signs of corrosion and rust.
  6. Remove vegetation growth (if any) from the solar hot water panel shading.
  7. Wash the collector panel with water or mild detergent (no solvents or acids)
  8. Regularly flush the hot water storage tank to remove sediment
  9. Make sure the pressure relief valve (which comes with the liquid solar water heating collectors) isn’t closed or stuck open.
  10. Ensure the anti-freeze solutions are working properly. If they need replacement, hire a qualified technician for the job.

Pro Tip: Constant flow of water exposes the water heaters to rust. This, in turn, might lead to the heater’s failure. To keep your solar water heating system corrosion-free for long, dry it out during the summer months when you aren’t using it. Drain the pipes and collectors regularly, too.

Frequently Asked Questions

How much does a solar water heater cost?

The average cost for installing a solar water heater in the US is between $8,000 and $10,000. However, if you opt for a heater with a smaller tank that holds up to 60 gallons, you may have to fork out only $4,000. At the high end, if you opt for a 120-gallon tank, you pay as many as $13,000.

How long do solar water heaters last?

One reason why many people prefer solar water heaters over standard gas or electric water heaters is because of their average life expectance. An average solar water heater can last more than 20 years, much longer than other domestic water heaters.

Do solar water heaters work at night?

Solar water heaters do not work at night because their collectors have no solar energy to convert into heat. However, that doesn’t mean that the water in the storage tank will go cold. Instead, if it’s protected by adequate insulation, the water will experience only 5 to 7*C loss in temperature over a period of 12 hours. This means you should still be able to get hot water on opening your faucets. 

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