Peak Sun Hours By Region: What’s Best For Solar

What are Peak Sun Hours?

solar energy production estimate is done by using the variable Peak Sun-Hour (PSH) times the power of the solar photovoltaic system in watts. Peak sun hours are not the same as “hours of sunlight” which is the total hours from sunrise to sunset. Instead, peak sun hours are the average solar radiation a certain location receives throughout the day. Its unit is kWh/m2 per day.

A peak sun hour is defined as an hour in the day when the intensity of the sunlight reaches an average of 1000 watts/meter². For example, a location that gets 5 PSH (kWh/m²), means that area gets 5 hours of solar power when the average intensity of sunlight is 1000 watts/meter².

Now let’s do an example of energy calculation of a solar photovoltaic system using the peak sun hours. Say we have a 5kW solar photovoltaic system in Raleigh which gets 5 peak sun hours as an annual average. Knowing the system wattage and peak sun hours we can find out how much energy the system will produce annually:

• Daily Energy: 5 kW x 5 hours (PSH) = 25 kWh
• Annual Energy: 25 kWh x 365 days = 9125 kWh

For simplicity, these numbers don’t represent any real world degradations, losses and inefficiencies.

Electric utility companies’ bill their customers using Kilowatt-Hour (kWh) as a standard unit of energy. We also get a kWh number for the system by multiplying peak sun hours with the solar system size. This way you can easily calculate your solar offset from your total annual electric utility usage in kWh.

How Many Hours of Solar Production Are There Per Day in North Carolina?

Peak sun hours can vary depending on region and exposure to the sun. 8MSolar engineers know that in North Carolina, the average peak sun hours value averages from 5 to 5.5. Throughout the year peak sun hour values change depending on the tilt of the solar modules. A system tilted at 35 degrees in Raleigh will have an average 3.8 PSH in January, in May the average will go to 5.7. Going up and down throughout the year, Raleigh’s peak sun hour PSH average is 5 annually. Charlotte’s average is also 5 peak sun hours annually and so on.

Peak sun hour values also depend on solar modules angles in relation to the sun. For example, a south facing roof pitched at a 50 degree angle in Raleigh gets 4.8 PSH annual average compared to 5 PSH average for a 35 degree tilt.