Fairfax Solar Power Information & Peak Sun Hours
Solar Green Energy Summary for Fairfax, Virginia
Lattitude: 38.8531
Sunlight
Fixed Tilt Sunlight Hours: 4.7 hours per day
1-Axis Tilt Sunlight Hours: 5.8 hours per day
2-Axis Tilt Sunlight Hours: 6 hours per day
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 that the latitude of Fairfax is 38.9 can be helpful for understanding total sunlight hour variance. As you approach the equator latitude approaches zero. The closer the latitude is to zero, the more consistent the daily sunlight hours are throughout the year. Total sunlight hour consistency simply makes planning for your solar power needs easier, but it is certainly not a requirement.
You will notice that the average peak sun hours for Fairfax change based on the type of panel being used. The reason for this is quite simple. A fixed panel does exactly what it sounds like, remains fixed in one position at all times. A 1-axis and 2-axis panels have axis that allow them to rotate. The 1-axis rotates with the sun's daily east to west movement while a 2-axis also adjusts for seasonal changes.
Climate in your geographical region is a major factor that will influence average peak sun hours per year. If you live in a region that does not have a lot of completely sunny days, then cloud coverage will greatly influence solar insolation on any given day. Mountains and trees may also contribute to lower solar insolation if they block the sun from your panels at any given point of the day.
For a fixed mounted solar panel in Fairfax, meaning that the solar panel will not track the sun in the sky, once can expect about 4.7 average peak sun hours per day. A 1-axis mount would increase this number to 5.8 hours per day because the panel would be facing the sun throughout the day. A 2-axis system that tracks the sun in the sky every day of the year would get approximately 6 hours per day in Fairfax.