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Peak sun hours is one of the most important criteria to examine when considering installing a solar power system. Peak sun hours are different than total sunlight hours in a day because the strength of the radiation of the sun varies throughout the day. For example, during sunrise and sunset the solar insolation from the sun is less powerful than at noon. For a moment of sunshine to be considered a peak sun hour the intensity needs to be at least 1 kilowatt per square meter. This means that a square meter of your solar panel should be receiving 1 kilowatt of energy from the sun. This number is used because it is an amount of light that allows a solar panel to produce output efficiently and not under perform due to lack of sunlight power.

Knowing that the latitude of Charleston is 39.5 can be helpful for understanding total sunlight hour variance. As you approach the equator latitude approaches zero. The closer the latitude is to zero, the more consistent the daily sunlight hours are throughout the year. Total sunlight hour consistency simply makes planning for your solar power needs easier, but it is certainly not a requirement.

You will notice that the average peak sun hours for Charleston 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.

Climate in your geographical region is a major factor that will influence average peak sun hours per year. If you live in a region that does not have a lot of completely sunny days, then cloud coverage will greatly influence solar insolation on any given day. Mountains and trees may also contribute to lower solar insolation if they block the sun from your panels at any given point of the day.

We can take the latitude of Charleston 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, Charleston will receive 4.7 average peak sun hours per day. This number can be increased to 5.6 hours by using a 1-axis tracking mount, or 6.4 hours from a 2-axis tracking mount.