Solar Panel Efficiency

Getting the Best Solar Panel Efficiency and the Factors that Affect it

Getting the Best Solar Panel Efficiency and the Factors that Affect it

The solar panel efficiency rating measures what percentage of sunlight hitting a panel gets turned into electricity. High efficiency doesn’t mean better, it just means you use less space for the solar array. Efficiency isn’t usually a big concern unless there is an unusually small space for the solar panels. The typical solar panel efficiency rating is around 14-18% efficient. That might not sound like much, but this average will produce enough power with the typical roof space.

Factors that Affect Solar Panel Efficiency

Besides solar panels efficiency and size, there are other factors that affect how much power your solar panels will create. Living in Arizona will get more solar radiation than someone who lives in the mid west. Solar energy output is also affected by weather and seasonal variations. The angle of the sun to the solar panel changes with the time of day and seasonal variations. Cloudy and rainy days also contribute to less effectiveness of the sunlight collection.

Solar Panel Pitch and Orientation

A non-tracking PV systems in the Northern Hemisphere should face true south. The positioning angle directly relates to the angle of latitude, if you live at 35.2 degrees North of the equator (Flagstaff, AZ), your panel should face directly South at a 35.2-degree angle. Remember that if the solar panels are being installed on a roof, take into account the pitch of the roof.

For maximum performance adjust your solar panels twice a year. In the summer months the sun is high overhead, catch more sunlight by tilting solar panel at a lower angle. During the winter, the sun moves across the sky at a lower angle, angle solar panels higher during these months. Large commercial systems have solar tracking systems that automatically follow the sun’s tilt through the day. Due to their high costs, they are not typically used for residential solar installs.


High temperature can severely reduce the solar panel’s production of power. Higher temperature increases the conductivity of the semiconductor, charges become balanced within the material, reducing the magnitude of the electric field, inhibiting the charge separation, which lowers the voltage across the cell. Depending on the location, heat can reduce the output by 10% to 25%.

In the built environment, there are a couple of ways to deal with high temperature. Install solar panels on a mounting system a few inches off the roof, this will help cool them by allowing air circulation. Use photovoltaic panels that are designed to be more efficient in hotter climates. Ensure that panels are constructed with light-colored materials, to reduce heat absorption. Inverters and combiners can be moved into the shaded area behind the array.


Shade can be the enemy of solar power. The way solar is designed even a little shade on one panel can shut down solar production on all the other panels. Solar cells are connected in series, and will operate at the current level of the weakest cell, if one solar cell is shaded it will adversely influence the output of all other cells. When deciding on a location for your solar panels do a shading analysis, make sure no shadows will fall on the solar panel array during peak sunlight hours. This may mean trimming a few trees.

Front surface soiling

Solar cells can not absorb light as effectively when the surface of the solar panels are covered with dirt or pigeon droppings, which doesn’t get washed by the rain. Making frequent physical inspections and spraying water on your modules can help reduce the problem.

Find solar technology bewildering? Best way to choose solar equipment in serving all of Arizona is to contact Pur Solar, we can look at your site and find the exact design and products that will work best for the conditions you have.

Find Out How Much Pur Solar Could Save You!

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