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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.

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.

Depending on your output needs, to get more out of your solar panels you can either upgrade your technology, buy more panels, or buy different tracking type panels. A fixed solar panel remains fixed at one angle throughout the year. A 1-axis panel will produce more output because it follows the path of the sun from sunrise to sunset to maximize sun exposure. Even more productive is a 2-axis panel that not only follows the sun's path throughout the day, but also accounts for the more subtle sun changes throughout the year with the different seasons.

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.

Using the latitude of Danville along with historical data of sunlight and weather patterns we can estimate that a fixed mounted solar panel will receive an average of 4.3 hours per day in this area. That number can be increased with better technology including add a 1-axis or 2-axis tracking mount, which would increase the average peak sun hours per day to 4.7 hours and 6 hours, respectively.