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If you put your solar powered math calculator in your backpack it will turn off from the lack of sunlight needed to power the device. As you slowly open your backpack and begin to let sunlight in, the calculator will eventually turn on when the amount of sunlight is enough to power the calculator. Similarly, peak sun hours refer to the hours of they day where the sunlight is strong enough to power a solar panel. This is different from total sunlight hours, which is simply the amount of hours in a day when there is any sunlight.

Sunlight hits the earth directly at the equator. This is why the equator has a latitude of zero degrees. The latitude of Atlanta is 40.3. Knowing the latitude of Atlanta can help you plan for your solar panel setup, as the larger the latitude the more variance you will see throughout the year for total daily sunlight hours.

Although most things are out of our control, like the sunrise, sunset or the weather, we can control the angle and the kind of mount we use for a solar panel. The angle of the solar panel, if using a fixed mount, should generally be around the angle that is equal to the latitude of the location to maximize output. In the northern hemisphere, panels angles should be lower in the winter months and higher in the summer months As a fixed mount is set, it is ideal to place it at an angle that will capture the most sunlight during the year. A 1-axis tracking solar mount will track the sun across the sky from sunrise to sunset, but the angle will remain the same throughout the day. A 2-axis solar mount will track the sun throughout the day from East to West, but the angle will also change automatically as the seasons change and the angle of the sun in the sky changes. Thus, a 2-axis will have a higher rating of peak sun hours compared to the 1-axis or fixed.

There are more variables than latitude that can change average peak sun hours. Weather patterns and geography will influence solar insolation that reaches your system. Thick grey storm clouds for example will block out a lot of the sun to the point where there may be no peak sun hours in the middle of the day when the sun is usually very powerful. Trees and mountains can deflect the sunlight, so be sure your solar panel is selectively placed.

In Atlanta the average yearly peak sun hours for a fixed tilt non-tracking solar panel mount is 4.3. This is for a fixed panel mounted at an angle that is equal to the latitude of the location for the entire year. The amount of peak sun hours increases to 5.6 hours if you are using a 1-axis panel, and to 6.4 hours if you upgrade to a 2-axis solar panel.