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Peak sun hours are a vital measurement to understand when considering the installation of solar panels. Peak sun hours are not the same as total sunlight hours because not every hour of sunlight during the day has enough strength and solar insolation to qualify as a peak sun hour. The rule of thumb is that a peak sun hour is when the intensity of the sun that is hitting your solar panel is providing at least 1,000 watts per square meter. This is an arbitrary number, but it is a number where most solar panels will be producing an efficient output and not underperforming due to sunshine that is not strong enough or direct enough.

Knowing the latitude of Johnston will help estimate average peak sun hours for your area. The latitude is used to accurately estimate the time of sunrise and sunset, thus giving you the total hours of daylight each day. Once you know the total hours of daylight, you can estimate the amount of peak sun hours based on a number of variables such as weather, time of year, the angle of the solar panel.

There are a few ways to increase average peak sun hours per year for your solar power system. One way is to use a tracking mount solar panel instead of a fixed tilt solar panel. A 1-axis mount will track the sun throughout the sky from sunrise to sunset, giving your panel a more efficient facing direction towards the sun throughout the day. A 2-axis solar panel will track the sun in the sky throughout the day, but also change and follow the angle of the sun in the sky throughout the year. Both of these axis system solar panels will produce higher average peak sun hours than a fixed solar panel.

Another reason to consider average peak sun hours is because weather can dramatically affect the day-to-day output of solar panels. It goes without saying that a dark stormy day will produce less output than a clear sunny day. Looking at a yearly average helps account for these daily variables.

By taking the latitude of Johnston 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 Johnston one can expect close to 4.8 average peak sun hours per day. With a 1-axis tracking mount you would get 6.9 hours per day, and 7.1 hours per day with a 2-axis tracking mount that tracks the sun everywhere in the sky.