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When trying to calculate your solar power needs there are a variety of factors to consider. Panel type and location, electricity needs, number of panels needed etc. One key to figuring out the math is factoring in the average peak sunlight hours in a day. Unlike total sunlight hours, peak sunlight hours are only when the sun is strong enough to power your solar panel. Using this number can help determine your needs to power your home or business in Gretna, Virginia.

The latitude of the location is important for measuring peak sun hours. The latitude determines how much overall sunlight there will be in a day. With a given latitude, time and date, one can accurately determine when sunrise and sunset will occur. Areas with latitudes closer to the equator will have a more consistent range of solar insolation throughout the year. Whereas areas closer to the poles will have a greater variance during the summer and winter months due to their higher latitudes.

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.

Since we know the latitude of Gretna we can take the average amount of total sunlight hours and estimate that with a fixed solar panel there would be an average of 4.8 peak sun hours per day. 6 hours per day with a 1-axis tracking mount that tracks the sun from sunrise to sunset, and 6.2 hours with a 2-axis tracking mount that tracks the sun everywhere in the sky.