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The amount of hours from sunrise to sunset is equal to the total sunlight hours in a 24 hour period. Similarly, peak sun hours are the amount of total sunlight hours in a 24 hour period that are strong enough to provide power from being captured by a solar panel. Not every hour of sunlight delivers the same amount of energy resources. The sunlight at sunrise does not provide as many resources as the amount of sunlight mid-day. Thus, looking at the average peak sunlight hours for Lewiston is valuable for calculating your solar needs.

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 Lewiston is 42.0.

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.

The sunrise and sunset is very predictable every day, but things like cloud coverage and weather are less predictable and vary daily and annually. If a location that is usually very sunny experiences a huge increase in storms and cloud coverage in a given year than the average peak sun hours for that day or year will probably decrease. Tall objects such as trees and buildings can block out the sun during high solar insolation times, so be sure to strategically place your solar panels to get better efficiency.

Using the latitude of Lewiston along with historical data of sunlight and weather patterns we can estimate that a fixed mounted solar panel will receive an average of 6.4 hours per day in this area. That number can be increased with better technology including add a 1-axis or 2-axis tracking mount, which would increase the average peak sun hours per day to 7.6 hours and 8.7 hours, respectively.