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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 4.4 per day can help you determine the amount of solar panels you need to install to power your home or business in Saint Paul, Iowa.

Although you can easily predict sunrise and sunset hours each day to the minute, looking at latitude can help with your solar planning. The closer you get to the equator the closer your latitude gets to zero. Sunlight hours on the equator are consistent throughout the entire year. Places further from the equator can have large variance in daily sunlight. For example higher latitudes can have very long summer days with lots of sunlight and very dark winters. The latitude of Saint Paul is 40.8.

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.

The sunrise and sunset is very predictable every day, but things like cloud coverage and weather are less predictable and vary daily and annually. If a location that is usually very sunny experiences a huge increase in storms and cloud coverage in a given year than the average peak sun hours for that day or year will probably decrease. Tall objects such as trees and buildings can block out the sun during high solar insolation times, so be sure to strategically place your solar panels to get better efficiency.

For a fixed mounted solar panel in Saint Paul, meaning that the solar panel will not track the sun in the sky, once can expect about 4.4 average peak sun hours per day. A 1-axis mount would increase this number to 6.2 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 7 hours per day in Saint Paul.