How to Calculate Maximum PV Panel Production
1) PV Panels are typically rated at 125% of their actual production,
so you must first multiply the Array’s rated maximum power output
by 80% to get it’s actual maximum power output.
2) Multiply the actual maximum power output by the number of
hours of “full sun,” or Peak Sun Hours (PSH) in the day *. This value
is different for each day, but the approximate values for our latitude
(33oN) are 4.61 hours in January and 6.89 hours in August. These
two values give you the maximum power production of the Array in
winter and summer, respectively.
3) The actual power production will be diminished by haze, dust,
atmospheric moisture, and, of course, clouds.
*
Note, the hours of “full sun,” or PSH, in one day is numerically the same as the solar insolation for
that latitude. To explain this, the amount of sun power received at the surface of the earth is called
“solar irradiance.” The maximum value for solar irradiance, when the sun is directly (90 o) over head is
approximately 1 kW / m2. This is called “Peak Sun” or “Full Sun.” The power produced by a PV
panel is proportional to the solar irradiance it receives. It will produces it’s actual maximum power
when it receives Peak Sun.
The solar insolation is the number of kW hrs / m2 that falls on an area of the earth’s surface during the
day. It is the energy accumulated on a given area over one day. Since it is expressed in kW hrs/ m 2,
and Peak Sun is 1 kW / m2 , it represents the equivalent amount of Peak Sun received in one day, which
is the PSH. The total energy produced by a PV panel each day is proportional to the Solar Insolation it
receives. Mathematically,
Solar Insolation (kW hrs / m 2 day) * Panel’s Actual Power (W) = Energy Produced (W hrs)
Peak Sun (1kW / m 2)
day
or
PSH = Solar Insolation
day
Peak Sun
and
Energy Produced per day = PSH * Panel’s Actual Power
where kW = kiloWatt (power), kW hrs = kiloWatt hours (energy), and kW hrs / m 2 day = the amount
of (sunlight) energy received over 1 square meter of area (m 2) per day, PSH = Peak Sun Hours,
and Peak Sun = 1kW/m2
Article written by Gregory Robert Hill / 2023 rev. 3/2024