Solar Water Heater Panels
Sizing and Installing Tips

Solar water heater panels or solar collectors are the most important elements of the sun-powered water heating system. Find out how to build a panel, tips on buying panel kits and mounting hardware, explore small portable panels for RVs, DIY panel books and more.

Solar panels are designed to absorb the sun’s heat energy (sun radiation) and used in water heating, for example, or produce electricity. With the selective coating applied on the absorber plates, the absorption efficiency increases. Inside the solar panel, a thermal fluid circulates and absorbs the heat energy and further through the plumbing system to the storage tank.



There are several types of solar panels for water heating you can buy, or build, and which type you will install depends on the region and climate including the temperature of the application:

  • Glazed flat-plate solar panels
  • Unglazed flat-plate solar panels
  • Evacuated tubes
  • Parabolic-through collector
  • PV panels

PV panels are designed to produce electricity from sun’s heat energy, and not for heating. In solar water heating systems, they can be used to run the pumps and controllers, for example, making the system energy independent.

Solar water heating panels that we will cover here are actually glazed flat panels, consisted of the flat-plate absorber with the coating for high absorption ratio, installed in a frame (box).

A solar panel frame has the insulation panel, while the cover is usually made of the tampered single or double layer glass, for the greenhouse effect (to keep the heat inside the panel longer). Glazed collectors are ideal for moderate temperature applications for domestic water heating, space heating or for pool heating.

Sizing tips

Sizing a solar water heater panel depends on the area where you live. If you live in the northern and colder parts of US, you need more square footage of the collector than if you live in the southern parts. Always consult the local plumber and code requirements.

Example: If you need 20 gallons of hot water per day, and for the family of four or more the water heater tank should provide at least 80 gallons of hot water. The recommended collector size for such a demand will be around 48 square feet or 4'x12' surface area.

Orientation tips

The orientation of solar water heater panels is very important for the solar panel efficiency and free solar heating. Between 30 and 65% of the sun's heat energy goes through the cover of the solar panel and heats the water that circulates through the tubing installed inside the panel box.

This is the reason why you need an efficient solar panel or collector. The perfect orientation for the collector is when it is perpendicular to the sun's rays.

This is an ideal orientation. You can always try to automate the system by investing in the necessary equipment. Such a control will always orient panels toward the sun, keeping the angle close to the perfect, but it requires lots of money, time and professional installation.

Majority of the solar water heater panels are installed facing the south, southeast or southwest - at the specified angle, and with the goal to have a full exposure during the major sunlight hours, which is two hours after the sunrise and two hours before the sunset, and when the sun is approximately 30 degrees above the horizon.

Installing tips

A roof is the best place for installing the solar panels for water heating. A location should allow a short and easy access to the storage tank, so the heat is not lost if the pipes are too long. In modern home construction, the collectors are an integral part of the house, as they are designed to blend with the exterior. These built-in solar panels are installed flush or nearly flush with the roof surface.

Standard solar water heater panels should have a structural frame which is securely mounted on the roof (bolted) so they can resist the snow and wind loads, for example. At the same time, it is important to allow the proper roof drainage. If the solar panels are not flush with the roof surface install them 3-5" above.

Solar panel mounting hardware (mounting rails, clamps, brackets, bolts...) is available with a purchase of any solar heating system or as the separate kit or items. The mounting hardware allows you to install the panels on the roof, ground, top and side of the pole, RV...

PV panels are more flexible and easier to install, while solar panels for water heating have more restrictions.

Keep in mind that the roof installation increases the possibility of roof leaks. This is why it is important to seal every drilled hole and secure all the joints on the pipes to be watertight.

Another important factor to consider when installing the solar collectors is to have them accessible for the maintenance and service.

Solar panel ground mount is convenient, much easier than the roof mount, doesn't affect the look of your home and possible roof leak, and as long as it has the sun exposure majority of the day, go for it.

Either you install the panels on the ground or the roof, secure the area and the panel to reduce the risk of the breakage. During the winter time drain the pipes dry to keep the pipes from bursting during the freezing temperatures.

When deactivating the solar heating system, always cover the collectors with the material like cardboard or other sturdy light-blocking material.

Tips when building

When you build your own solar panel make sure to insulate it well to reduce the heat loss and have the efficient heat transfer; and to protect the inside (tubing) from the weather conditions. The trapped heat will then transfer the heat to the incoming fluid that is passing through the tubing.

The collector will get the maximum absorption and efficiency if the exposed surfaces (tubing) are painted in black.

The top of the collector should be made of the material which is transparent to the incoming sunlight and at the same time reduces the heat loss. A recommended cover should be made of the tempered glass with the low iron content. The advantage of the glass panel cover, over the plastic, is its durability, heat resistance, it can deteriorate less due to the outside conditions, but it is breakable.

If you live in the colder area, use the double layer glass so it can keep the heat longer inside the solar water heater panel.

The panel box should have drainage holes at the lowest point so it can drain the rain, condensation, etc. Use the aluminum for the collector casing as it looks better, doesn't corrode, and it lasts longer.

Panel kits, mounting hardware, portable RV panels and DIY solar panel books is my favorite online store where you can buy water heating equipment like collectors and PV panels, solar panel kits, books that are describing in details how to build panels, flexible panels for pools, small portable for RVs, roof and ground mounting hardware for installation ... or in short the whole solar panel systems.

Most of the manufacturers are providing 25-year warranty and their panels are designed for easy installation and maintenance-free service.

Solar charging kits are designed to provide free and clean power and are perfect for your RV, cabin, boat, battery charging and even home. The kit usually comes with the solar panels, mounting frame, power inverter, and controllers.

Foldable or flexible solar panels are a very convenient way of converting sun power into the electrical current, even in low light. Due to its multi-section design, they can be easily folded and stored. Solar cells are high-efficient and mainly used for charging electronics when camping, hiking, during power outages and whenever the portable power source is needed.

RV solar panel kits are designed with the solar charging kits, inverter, DC installation kit, transfer switch and other components making it ready for complete plug and play installation.

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