Napa Solar Power Information & Peak Sun Hours
Solar Green Energy Summary for Napa, California
Lattitude: 38.2982
Sunlight
Fixed Tilt Sunlight Hours: 5.9 hours per day
1-Axis Tilt Sunlight Hours: 6.6 hours per day
2-Axis Tilt Sunlight Hours: 8.3 hours per day
If you put your solar powered math calculator in your backpack it will turn off from the lack of sunlight needed to power the device. As you slowly open your backpack and begin to let sunlight in, the calculator will eventually turn on when the amount of sunlight is enough to power the calculator. Similarly, peak sun hours refer to the hours of they day where the sunlight is strong enough to power a solar panel. This is different from total sunlight hours, which is simply the amount of hours in a day when there is any sunlight.
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.
Weather is one of the major culprits that will cause inconsistent total peak sun hours for any given day. The sunrise and sunset will always be predictable every day, but the weather is hard to predict and cloud coverage can greatly diminish the efficiency of a solar power system on any given day. On the bright side, a location that is known to have cloudy weather a majority of the year could have unexpectedly more sunny days, so it can go both ways.
Since we know the latitude of Napa we can take the average amount of total sunlight hours and estimate that with a fixed solar panel there would be an average of 5.9 peak sun hours per day. 6.6 hours per day with a 1-axis tracking mount that tracks the sun from sunrise to sunset, and 8.3 hours with a 2-axis tracking mount that tracks the sun everywhere in the sky.