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It goes without saying that throughout the year the amount of sunlight in any given day is going to vary. The time of year and weather will have a strong influence on daily sunshine. Looking at the average amount of peak sunshine hours in a day during an entire year stretch is a valuable exercise when trying to determine the amount and type of solar panels you need to install to power your business or your home. 4.4 peak sun hours means that in Shirley on average there are 4.4 hours a day where the sun is strong enough for solar panels to harness its energy. This number is less than the amount of total sunlight hours in a day because there are times during the day (ex. sunrise and sunset) where the sun is not strong enough to benefit solar panels.

If you open the newspaper in the morning or watch the weather channel on the news you can get an accurate prediction of sunrise and sunset each day for Shirley. However, still knowing that the latitude of Shirley is 42.5 can be a helpful number for your solar panel setup and planning. The closer your latitude is to zero the closer you are to the equator. At the equator you find the most consistent total sunlight hours throughout any given day of the year. As your latitude increases you can see larger discrepancies of daily sunlight hours during the year. For example, having very long summer days and very short and dark winter days

Throughout the day the sun obviously moves throughout the Shirley sky. The suns position in the sky also changes throughout the year with the seasons. A fixed solar panel does not accommodate for these changes. However, a 1-axis panel rotates and follows the sun’s path during the day. A 2-axis panel both follows the sun’s daily path as well as the seasonal differences

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.

We can take the latitude of Shirley 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, Shirley will receive 4.4 average peak sun hours per day. This number can be increased to 5.6 hours by using a 1-axis tracking mount, or 6.3 hours from a 2-axis tracking mount.