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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 Graf, Iowa.

Although you can easily predict sunrise and sunset hours each day to the minute, looking at latitude can help with your solar planning. The closer you get to the equator the closer your latitude gets to zero. Sunlight hours on the equator are consistent throughout the entire year. Places further from the equator can have large variance in daily sunlight. For example higher latitudes can have very long summer days with lots of sunlight and very dark winters. The latitude of Graf is 42.5.

Throughout the day the sun obviously moves throughout the Graf 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.

For Graf the number of average daily peak sunlight hours for a fixed solar panel is 4.6 hours. If you are using a more efficient 1 or 2-axis panel then the number will increase to 5.9 hours for a 1-axis panel and 6.1 hours for a 2-axis panel.