How many kWh should a 14.4 kW DC system produce on a good day?

[raptor]

Hello! We just commissioned our 14.4 kW DC system on Aug 14. It has 36 panels 400 watts each. My highest daily PV production was 50.1 kWh yesterday Aug 23. System is in Fresno CA and yesterday was clear and sunny all day.

I think this is low for a system this size. Figuring about 5 hrs of good sunlight then the system should produce at least 72 kWh on a good day. Is this reasonable? My solar installer said 50 kWh is reasonable. Appreciate your insight.

 

[Tomthumb62]

Hello! We just commissioned our 14.4 kW DC system on Aug 14. It has 36 panels 400 watts each. My highest daily PV production was 50.1 kWh yesterday Aug 23. System is in Fresno CA and yesterday was clear and sunny all day.

I think this is low for a system this size. Figuring about 5 hrs of good sunlight then the system should produce at least 72 kWh on a good day. Is this reasonable? My solar installer said 50 kWh is reasonable. Appreciate your insight.

That’s very normal. Expect about 50-75% rated output. You’ll rarely see 100% output except in cool sunny weather like winter (unless your winters are usually cloudy).

 

[raptor]

@Tomthumb62 thanks for the reply. My other home has a 8.16 kW system and it produced 49.9 kWh yesterday. It is near Fresno so conditions are similar. Why would this system which is a lot smaller produce about the same?

 

[Mattb4]

Seems a bit low. But I do not know how your panels are mounted. 50100wh from 14400w worth of panels is only 3.5h of production. I would expect you to have around 4-6hrs. It only takes a small amount of shading however to really knock your numbers down. It could be a chimney, vent pipe, adjacent building or tree and you have much less than you would expect.

 

[Doggydogworld]

Hello! We just commissioned our 14.4 kW DC system on Aug 14. It has 36 panels 400 watts each. My highest daily PV production was 50.1 kWh yesterday Aug 23. System is in Fresno CA and yesterday was clear and sunny all day.

PVWatts says you should average 77 kWh AC per day in August with south facing panels tilted 35 degrees. Shading from nearby trees or structures, even your own chimney and other roof protuberances, can reduce that significantly.

You other system seems closer to average. Is there a big difference in panel cooling or other factors?

 

[raptor]

Both systems are ground mount. Temp at both locations are about the same. All panels have same orientation.

 

[raptor]

PVWatts says you should average 77 kWh AC per day in August with south facing panels tilted 35 degrees. Shading from nearby trees or structures, even your own chimney and other roof protuberances, can reduce that significantly.

You other system seems closer to average. Is there a big difference in panel cooling or other factors?

Thanks! I will check PVWatts. Both ground mount systems with all panels orientated same direction

 

[raptor]

Seems a bit low. But I do not know how your panels are mounted. 50100wh from 14400w worth of panels is only 3.5h of production. I would expect you to have around 4-6hrs. It only takes a small amount of shading however to really knock your numbers down. It could be a chimney, vent pipe, adjacent building or tree and you have much less than you would expect.

The 14.4 system is elevated 10' ground mount all panels facing south. Yes I suspect that is low. Thanks!

 

[fromport]

Hello! We just commissioned our 14.4 kW DC system on Aug 14. It has 36 panels 400 watts each. My highest daily PV production was 50.1 kWh yesterday Aug 23. System is in Fresno CA and yesterday was clear and sunny all day.

I think this is low for a system this size. Figuring about 5 hrs of good sunlight then the system should produce at least 72 kWh on a good day. Is this reasonable? My solar installer said 50 kWh is reasonable. Appreciate your insight.

I am south of you in California. I roughly have a 15kW DC system and have some shading issues in the morning & afternoon.
My system produced 113 kWh yesterday.

 

[raptor]

I am south of you in California. I roughly have a 15kW DC system and have some shading issues in the morning & afternoon.
My system produced 113 kWh yesterday.

That is awesome! Something is definitely wrong with my system. : (

 

[Mattb4]

The 14.4 system is elevated 10' ground mount all panels facing south. Yes I suspect that is low. Thanks!

Since this is likely a grid tie setup is there anything that limits the amount that you can send to the grid?

 

[raptor]

Since this is likely a grid tie setup is there anything that limits the amount that you can send to the grid?

Not that I know of. I am under NEM2 with PG&E

 

[timselectric]

Napkin math estimates 57.4 kwh.

Oops.... 57.6 kwh
My napkin has beer on it. lol

 

[Doggydogworld]

Both ground mount systems with all panels orientated same direction

Based on PVWatts and your other system I'd expect 80-85 kWh AC on "good" days in August. I'm not familiar with NEM2, though, does it do curtailment on sunny days? Though that should just be a spring/fall thing.

If your installer won't troubleshoot it I'd pay someone who will and document everything very carefully. Ideally someone familiar with your inverter. Who installed the other system? Might be a good place to start.

 

[G00SE]

Are your charge controllers over paneled? Could there be peak production times that are simply clipping thus showing a reduced production

 

[Hedges]

How many PV strings?
How many MPPT?
With a clamp DC ammeter you can compare strings, see if some are outliers.

Have you gone over array & string design in terms of voltage and amps, in addition to watts? Any of those can get clipped.

 

[Lt.Dan]

Just for reference, I'm about 45 min south of you, with an 11kW system of various facings, and I am averaging 60-62kWh on good sunny days right now. (not including the AC Coupled PV I have)

I would suspect something wrong.

 

[raptor]

Based on PVWatts and your other system I'd expect 80-85 kWh AC on "good" days in August. I'm not familiar with NEM2, though, does it do curtailment on sunny days? Though that should just be a spring/fall thing.

If your installer won't troubleshoot it I'd pay someone who will and document everything very carefully. Ideally someone familiar with your inverter. Who installed the other system? Might be a good place to start.

Hey great estimate! Today I got 82.2 kWh from the system. It was clear and sunny all day. Yesterday I called the inverter manufacturer (Sol-Ark) tech support and they immediately identified that the "Solar Sell" button was off so the inverter was choking production to match the load. Wasted almost a month of production! I guess some solar companies are just nail pounders and know nothing about software configuration.

 

[raptor]

Just for reference, I'm about 45 min south of you, with an 11kW system of various facings, and I am averaging 60-62kWh on good sunny days right now. (not including the AC Coupled PV I have)

I would suspect something wrong.

Thanks for feedback. Today I got 82.2 kWh from the system. It was clear and sunny all day. Yesterday I called the inverter manufacturer (Sol-Ark) tech support and they immediately identified that the "Solar Sell" button was off so the inverter was choking production to match the load. Wasted almost a month of production! I guess some solar companies are just nail pounders and know nothing about software configuration.

 

[raptor]

How many PV strings?
How many MPPT?
With a clamp DC ammeter you can compare strings, see if some are outliers.

Have you gone over array & string design in terms of voltage and amps, in addition to watts? Any of those can get clipped.

3 strings. The installer actually wired them wrong but after correcting that it was still low. Today I got 82.2 kWh from the system. It was clear and sunny all day. Yesterday I called the inverter manufacturer (Sol-Ark) tech support and they immediately identified that the "Solar Sell" button was off so the inverter was choking production to match the load. Wasted almost a month of production! I guess some solar companies are just nail pounders and know nothing about software configuration.