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Peak sun hours is arguably the most important number to consider before installing your solar panels. Unlike total sun hours, peak sun hours are calculated by looking at the amount of sunlight hours in a 24 hour period that is strong enough to be absorb by a solar panel. One way to imagine peak sun hours is to think about a solar powered calculator you owned in school. If you covered the solar panel with your finger, or tried to use the calculator in the dark, the calculator would not work. As you slowly exposed the calculator to light the calculator would eventually turn on and be usable. The same is true with peak sun hours; these are the hours that your solar panels receive enough sunlight to work. Looking at the average peak sunlight hours of 4.5 per day can help you determine the amount of solar panels you need to install to power your home or business in Fall City, Washington.

Knowing that the latitude of Fall City is 47.6 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.

A tracking mount will increase the average peak sun hours for a solar power system. Think about a panel that is tracking the sun in the sky vs a panel that is fixed and not moving: you will see a higher efficiency ratio of productions. A 1-axis mount will track the sun from East to West from sunrise to sunset and move on a single axis of rotation. A 2-axis mount will track the Sun from East to West the same as a 1-axis mount would, but it will also track the angle of the sun in the sky as it slowly varies season to season. A 2-axis mount is more necessary in high latitude regions where the angle of the sun in the sky changes dramatically between each equinox.

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.

For Fall City the number of average daily peak sunlight hours for a fixed solar panel is 4.5 hours. If you are using a more efficient 1 or 2-axis panel then the number will increase to 6 hours for a 1-axis panel and 6.2 hours for a 2-axis panel.