In order to choose and install the right solar water heating system, it is important to take into account a number of factors: the size of the roof or land, solar resource availability, trees, and buildings shading the roof, along with the right orientation and tilt of your solar collector. An efficient solar water heater depends largely on how much energy your building site receives from the sun.

A solar water heater uses both direct and diffuse solar radiation. Even if your area isn’t predominantly warm and sunny, such as the southwest region of the U.S, there may still be an adequate amount of solar energy available. 

When building sites are unshaded and generally face the equator (primarily south in the United States), a solar water heating system is a good fit. The solar installation company or supplier near you can perform a site analysis for your solar system.

Avoid being shaded by trees or other buildings nearby.  Although shading can’t be avoided completely, it’s best to avoid it during the hours of 10 a.m. to 2 p.m. and during winter, around the time that the sun is at its lowest point (summer has a lower sun angle, which means less shading).

Roofing Type, Age, And Condition

It is important to consider the type, age, and condition of the roof. Solar heating can be easily installed on composite shingle roofs more easily and more affordably than those covered with wood shingles or tile. A new roof can be constructed around solar water heating collectors; however, new solar systems are best installed in new or sound buildings that will not require replacement within the 25-year lifespan.

In many cases, blocking between rafters is required to reinforce the roof structure. A professional roofer should be consulted when installing roof rack stanchions and waterproof flashing, as they are often the ones who perform this task.  It would seem that the roof is the most natural place to install solar collectors, but some solar collectors are installed on ground foundations (piles) to avoid roof problems.

The tilt and orientation of the collector will affect the efficiency of your solar water heating system. The solar contractor must take both factors into account when evaluating and sizing your solar system based on your site’s solar resources.

Collector Orientation

The orientation of solar hot water collectors should be based on the location of the sun in order to maximize their exposure to solar energy on a daily and seasonal basis. In general, the northern hemisphere is ideally suited for solar collectors oriented true south. Study results suggest, however, that based on your location and the tilt of your collector, it is possible to align it up to 45o east or west of true south without significantly affecting its performance.

It is also important to consider the orientation of your roof (if you intend to mount your collector on your roof), as well as local landscape features that shade your collector on a daily or seasonal basis, along with local weather conditions (cloudy mornings, rainy afternoons), since these factors may influence how your collector should be oriented.

Collector Tilt

In today’s climate, the majority of solar water heating collectors are mounted flat on the roof. This style has a more aesthetic appeal than rack-mounted collectors, which are mounted at odd angles to the roof. This means that most collectors tilt in the same direction as the roof.

It is best to tilt your collector at an angle equal to your latitude in order to maximize your annual energy delivery with maximum production in spring and fall. Due to the colder water coming in during winter, solar collectors for water heating are often tilted at a steeper angle to maximize efficiency. It contrasts with photovoltaic-type solar systems, which are typically mounted on flat roofs or tilted low. However, the roof angle will need to be considered when sizing your system.

Would you like to know how solar energy is collected? Read our blog to find out.


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