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The average peak sunlight hours of San Francisco is one of the most important numbers to understand when starting a solar power project in the area. Peak sun hours or solar insolation is a different number than just the total time between sunrise and sunset. It’s a number that represents the amount of hours per day that a solar panel will be receiving enough sunlight to convert energy into electricity at an efficient ratio.

The peak sunlight hours in San Francisco is not a fixed number. It can be higher or lower any given day due to a variety of external factors or from reasons within the solar panel system itself. Some of these external and uncontrollable factors are things like weather, cloud coverage, strength of the sun in a particular season, or problems with the grid system that are out of your control. For cities that are further from the equator for example, we will see greater change in average peak sun hours between the summer and winter months. For cities near the equator the variance will be less. Hence, the latitude of San Francisco is a crucial number for understanding the ebbs and flows of solar insolation throughout the year.

For variables that you can control that may affect the average peak sun hours received by a system are things like technology and the quality of the solar panels, the tilt of the solar panel, what kind of axis system is being used, and general maintenance and functionality of the system. F or example, a 2-axis tracking mount will most likely result in higher average peak sun hours in a year than using a fixed solar panel.

In San Francisco, the average peak sun hours for a fixed tilt panel mounted at the angle equal to the latitude of the city is hours. The more efficient 2-axis system that tracks the sun in the sky during each season will boost the average peak sun hours to hours per day in San Francisco.