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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 McHenry, Illinois.

If you’re using a fixed axis and fixed tilt solar panel, the ideal angle of the panel mount should be set at an angle equal to or close to the latitude of the location of the panel. Latitude is a valuable measurement to use when figuring how many daylight hours and the angle of the sun in the sky for your location. Since at locations with a higher latitude the sun will find itself at more variable angles in the sky throughout the year it is important to set the angle of the panel correctly and efficiently capture more peak sun hours. In the Northern Hemisphere the sun will be at lower angles in the Southern sky in the winter, and higher angles during the summer months, so the angle of the panel is crucial when trying to maximize output.

A tracking mount will increase the average peak sun hours for a solar power system. Think about a panel that is tracking the sun in the sky vs a panel that is fixed and not moving: you will see a higher efficiency ratio of productions. A 1-axis mount will track the sun from East to West from sunrise to sunset and move on a single axis of rotation. A 2-axis mount will track the Sun from East to West the same as a 1-axis mount would, but it will also track the angle of the sun in the sky as it slowly varies season to season. A 2-axis mount is more necessary in high latitude regions where the angle of the sun in the sky changes dramatically between each equinox.

The sun is a great ball of gas that rises and sets every day that the earth rotates while in orbit around the sun. Barring any major disasters this is a very predictable occurance every day. Latitude helps predict this even more, narrowing it down to the minute for sunrise and sunset. But some things aren’t as predictable that will greatly influence the efficiency of solar panels. Weather and cloud coverage for example can greatly diminish peak sun hours on any given day. Thick storm clouds will block a high percentage of the sun's rays, resulting in lower output of your solar panels. Weather needs to be factored into deciding when to use your system, or how much output one expects to get.

By taking the latitude of McHenry one can get a close estimate of the amount of average peak sun hours per day for the geographical area. It varies with technology and the type of solar panel mount you use, but for a fixed mount solar panel in McHenry one can expect close to 4.6 average peak sun hours per day. With a 1-axis tracking mount you would get 5.8 hours per day, and 6 hours per day with a 2-axis tracking mount that tracks the sun everywhere in the sky.