kWh to kWh/kWp?

[bernard]

I am a bit confused with this kWh and kWh/kWp units when it comes to PV panels.
Are these two the same? If not how to convert one to another?

Let's say I have a 4kW system, which annually generates 5000 kWh.
How to convert these 5000 kWh to kWh/kWp?

Thank you.

[inetdog]

I am a bit confused with this kWh and kWh/kWp units when it comes to PV panels.
Are these two the same? If not how to convert one to another?

Let's say I have a 4kW system, which annually generates 5000 kWh.
How to convert these 5000 kWh to kWh/kWp?

Thank you.

As I understand it, the units of kWp are really just the same as the units of kW, namely the power (rate of energy production) of the panels.
All the p does is qualify it as the peak (highest) power value seen during operation.
If the angle and other factors are optimal, the kWp will be related to the nominal STC or PTC kW of the panels, namely at specified temperature and with incident radiation of 1000w/m².

Now for any real world panel array, the actual kWp will be lower than the nominal panel power and if the panel angle is not optimal it will even be some constant factor lower than the nominal power.
The kWh is the energy produced during one day, one year, or whatever, so the kWh divided by the kWp is primarily an indicator of how good the location is (equator versus high latitude) and what the local weather conditions do to reduce total output for a given set of panels.

To convert your 5000 kWh per year to a kWh/kWp value you just need to know what the kWp of your array is.

[bernard]

To convert your 5000 kWh per year to a kWh/kWp value you just need to know what the kWp of your array is.

Thank you inetdog.
I am not sure how to do that.

[HX_Guy]

I've been wondering about the same thing recently...

My SolarEdge page shows "This Month Performance [kWh/kWp] = 99.07". So that means that the system is producing 99.07kWh per kW of system power? Makes sense as 99.07 x 12.4kW = 1228.47 and that matches my "Energy this month" which shows 1.23MWh.

[bernard]

Thank you HX_Guy.

But is kWh/kWp value always given for period of one month?
What if you had an inverse case: you knew how much your PV array outputs per year, and you would like to convert that to kWh/kWp (per year?)?

For the sake of simplicity let's say that your PV array outputs the same amount every months:
1.23 MWh * 12 months = 14.76 MWh per year = 14760 kWh per year

14760 MWh / 12.4 kW = 1190 kWh/kWp

Did I get that right?

[DanKegel]

I am not an expert, but:

If you have a 4kw array, then your kwp (kilowatts peak) is 4. kwp is the faceplate rating of your array.
If it generates 5000 kwh per year, then kwh/kwp/year is 5000 / 4 = 1250, and kwh/kwp/month = 1250 / 12 = 104.

For what it's worth, my kwh per kw per day averages out to 4.5 over the entire year here in sunny los angeles.
And 4.5 kwh per kw per day is about 130 kwh per kw per month (because 4.5 * 30 days/month = 130).

[bernard]

Very nice reply.
Thank you Dan.

When you say that in Los Angeles you get 4.5 kWh/kWp/day, is that the same as: 4.5 kWh/m2/day
(an average daily solar radiation per year)?

[DanKegel]

When you say that in Los Angeles you get 4.5 kWh/kWp/day, is that the same as: 4.5 kWh/m2/day
(an average daily solar radiation per year)?

They're vaguely similar in that each is higher for more efficient panels and lower in shady or cloudy places or times, but the units are different, and the numbers are not identical.
kWh/m2/day is "output in kWh per area per day".
kWh/kWp/day is "effective hours of full sunshine per day".

Roughly speaking, anyway.

[gregvet]

Very nice reply.
Thank you Dan.

When you say that in Los Angeles you get 4.5 kWh/kWp/day, is that the same as: 4.5 kWh/m2/day
(an average daily solar radiation per year)?

The kWh/kW(DC) really is an efficiency number indicating the kWh produced for each kW DC of your system over a given period. For instance, I have 33-235 watt panels giving a 33*235 = 7.755 kW DC system. I generate an average of 45 kWh per day now in March. The efficiency is therefore 45 kWh/7.755 kW = 5.8 kWh/kW/day