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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.

The latitude at the equator of the earth is zero degrees. This is where sunlight strikes the earth most directly. Due to the earth's curved shape, sunlight hits at a various angles depending on location. As latitude increases, the further you are located from the equator and more variance you see in sunlight hours. The latitude of Ellison Bay is 45.3.

You will notice that the average peak sun hours for Ellison Bay change based on the type of panel being used. The reason for this is quite simple. A fixed panel does exactly what it sounds like, remains fixed in one position at all times. A 1-axis and 2-axis panels have axis that allow them to rotate. The 1-axis rotates with the sun's daily east to west movement while a 2-axis also adjusts for seasonal changes.

Another reason to consider average peak sun hours is because weather can dramatically affect the day-to-day output of solar panels. It goes without saying that a dark stormy day will produce less output than a clear sunny day. Looking at a yearly average helps account for these daily variables.

We can take the latitude of Ellison Bay and use that number to know the amount of total sunlight hours in the region from sunlight to sunset and estimate that with a fixed solar panel, Ellison Bay will receive 4.3 average peak sun hours per day. This number can be increased to 5.3 hours by using a 1-axis tracking mount, or 5.6 hours from a 2-axis tracking mount.