# Actual Output of an Array

Registered Users Posts: 63 ✭✭
If I have an array of 12.15kW I know that I can't get all 12.15kW out of the array. If I want to determine the nominal watts I would have available what kind of factor would I need to use. Currently in my calculations I am using 80% so my 12.15kW array will give me a nominal output of 9.72kW. Is that a good factor to use for calculations?

Thanks,
Eric

• Solar Expert Posts: 5,996 ✭✭✭✭✭
Eric, You should be able to look up your Normal Operating Cell Temperature Values (NOCT) These usually run about 75% of the panels rating, I guess you understand that their are other system losses.
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Registered Users Posts: 63 ✭✭
Photowhit said:
Eric, You should be able to look up your Normal Operating Cell Temperature Values (NOCT) These usually run about 75% of the panels rating, I guess you understand that their are other system losses.
I will look for the NOCT in the specs.

Yes I understand there are many other losses in the system and I think I am taking care of them in my calculations.
I use ~77% for Solar Panels through GT AC inverter (vs predicted hours of sun)--That will get you within 10% of your average output energy over time (a bit on the conservative side for colder climates--Hot panels produce less Vmp-array, and less power).

For wiring and such... I always suggest a minimum of 1.25x your expected rated current to keep the wiring cooler and not have false trips on fuses and circuit breakers.... I.e., 15 amps continuous current in cable * 1.25 = 18.75 ~ 20 amp branch wiring+breaker ratings).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 4,496 ✭✭✭✭✭
In Colorado, altitude may also be a factor. High altitude means less atmosphere for sun to get through and cooler temps means higher production.
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Registered Users Posts: 63 ✭✭
I am in a high valley at 7800ft. The sun is crazy strong up here and the temps rarely get above 80 in the heat of the summer.
• Registered Users Posts: 4,496 ✭✭✭✭✭
On a nice spring day with a breeze from the north keeping the back of the panels cool, you should see some pretty good output!
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Registered Users Posts: 63 ✭✭
The only problem with the nice spring breezes here is that we almost always have wind and usually strong. Today it is showing 35mph gusting to 51mph, so I have to make sure my mounts are ready for the wind.