How to evaluate health of a new system?

[sensij]

There is a weather station set up not too far from the OP's zip code that reports hourly GHI data. Because the locations are different and the correlation between GHI and energy generation is not particularly straightforward, there are limitations to this approach. The PVOutput.org comparison is probably a better and more user friendly comparison. However, for what its worth, here is a plot of the daily GHI vs the daily energy generated, from 11/1 to today. Over time, if the correlation drifts in ways that can't be explained seasonally or by panel tilt, it could be an indication of a change in performance in either the weather station, or the PV array.

Data.PNG

[sensij]

Here's a source that break down by month and by specific equipment, shading etc. Its the CA state calculator.

Do you mean the CSI EBPP calculator? According to the documentation, it is a repackaged version of PVWatts that allows specific equipment to be selected. The text that matters:

While this calculator relies on industry-standard assumptions, and is driven by NREL’s PV Watts v. 2 calculator, there may be other factors that affect the output of your PV System.

When I set the current version of PVWatts to the CSI default derate (16.3%) and match the inverter effeciency to what is used by CSI, the results come out almost identically. The new version of PVWatts uses a lower default derate (14%), which they have indicated is a better fit to real world data the results have been compared against.

The CSI equipment database is comprehensive, better than what comes packaged by NREL in SAM. Maybe there is a way to update it...

[SoCalsolar]

here's a source that break down by month

Here's a source that break down by month and by specific equipment, shading etc. Its the CA state calculator.

[bcroe]

Honestly, I don't know. I have a single FRONIUSs IG Plus 6.0-1UNI with 24 250W Solarworld panels....I'm not sure the number of "strings" or other details. I don't really have any easy way to test anything on the 2nd story roof, but I have easy access to the inverter. What is the typical hookup for this equipment? Would I benefit from asking any specific questions regarding strings etc?

The most suspicious detail at this point is how low my "peak" output has been since the first week on November; only 1 day with a peak over 4kW (just barely) since Nov 19th. I'll have to keep an eye on the production numbers as it gets sunny...

The arrangement of 2 strings of 12 is likely; 3 strings of 8 is possible. If you have have a combiner
box, you can observe the arrangement, and make measurements there. Your FRONIUS has the facility
to fuse strings and DC disconnect internally. If you see 4 or 6 wires approx 10 gauge coming into it,
those are from your strings. The wires might be labeled, or can be traced to the + and - terminals
visible on the left when the lower door is opened, and the cover removed.

The criteria for clamp on comparisons, is the strings must be identical and in good sun. I'd measure
the + wires here. My FRONIUS 6.0 has bus bars below the + and - inputs, with single heavy wires
going to a remote combiner. Bruce Roe

[Alisobob]

I'll have to keep an eye on the production numbers as it gets sunny...

You had a week classified as "Sunny"... I'd have the installer out asap.

[sensij]

Honestly, I don't know. I have a single FRONIUSs IG Plus 6.0-1UNI with 24 250W Solarworld panels....I'm not sure the number of "strings" or other details. I don't really have any easy way to test anything on the 2nd story roof, but I have easy access to the inverter. What is the typical hookup for this equipment? Would I benefit from asking any specific questions regarding strings etc?

The most suspicious detail at this point is how low my "peak" output has been since the first week on November; only 1 day with a peak over 4kW (just barely) since Nov 19th. I'll have to keep an eye on the production numbers as it gets sunny...

The typical connection for this system would be two parallel strings of 12 panels in series. That inverter appears to only have a single MPPT, so if all of the panels do not see uniform radiation, it may handle it less efficiently than inverters with separate MPPT for each string.

[insaneoctane]

... How are your panels connected?

Honestly, I don't know. I have a single FRONIUSs IG Plus 6.0-1UNI with 24 250W Solarworld panels....I'm not sure the number of "strings" or other details. I don't really have any easy way to test anything on the 2nd story roof, but I have easy access to the inverter. What is the typical hookup for this equipment? Would I benefit from asking any specific questions regarding strings etc?

The most suspicious detail at this point is how low my "peak" output has been since the first week on November; only 1 day with a peak over 4kW (just barely) since Nov 19th. I'll have to keep an eye on the production numbers as it gets sunny...

[Alisobob]

solar14.JPG

This is my output for 92656 on a 6.5 KW system.

You can see how weeks 2 and 3 under performed weeks 1 and 4.

Weather made a big difference in the weekly output.

watt.JPG

The only thing that jumps out at me is for these dates, you had sunny conditions and averaged about 15 KwH's per day. For these same dates, I also had sunny conditions, but averaged 28 KwH's per day. A considerable difference.

watts2.JPG

[bcroe]

Now that my system has been operational for just over a month, I'm disappointed with my 6kW system's first month production. From Nov 1 to Nov 30 my 6kW system producted 488kWh. The only thing I have to compare to that is my PVWatts prediction of 730 kWh. Since the system is new and I don't have a lot of data, how do I identify a "problem"? If I had a bad panel, for example, what would my overall system output look like? I see that the first week of running my system was, by far, my best. Then it's gone down hill since then. This last week weather has been poor, but I just am not sure. By the way, my installer doesn't guarantee production. If there is something wrong, they will fix it, but how would I prove something is wrong? Here is my data. I've manually added the weather "condition" per www.wunderground.com for a zipcode that is 7-8 miles away (my zipcode wasn't available). That might help, but it shows sunny days where my production was low. Any advice? I know I'm only 1 month into this, but if I have an equipment issue, I'd rather ID that sooner than later. Thanks for your input/thoughts....

Days with very good sun are best for troubleshooting. I use a clamp on DC ammeter to compare
identical strings, which should have nearly identical output. A bad string shows up immediately;
finding the exact fault takes longer. How are your panels connected? Bruce Roe

[MGE]

Im in San Diego and have a 7.6kw AC system that generated 699kw hrs for this past month of November. Last year I generated only 643kw hrs. I think the PV watt estimate was 738kw hrs. Had a lot of cloudy days here on the coast so I'm not surprised on the output. I overproduced from April through Sept of this year so I guess I can't complain. My first year generating I was 238kw hrs under the PVwatt estimate, we'll see how the second year add's up when April 15 of 2015 comes around. So far so good.

[silversaver]

By looking at the graph of your system vs. the 7kW in your area, I don't see any difference to worry about.....

My 7.1kW SW 245 with 23 deg tilt only produced 701kWh during Nov 2014. I bet lots smaller system outperform me but I think I'm on the track comparing with few system in my area.

[J.P.M.]

Not likely in S. Cali. Probably same as here in Arizona: our worst month is December by far.

Worst month is Dec. Nov. & Jan. are about 8% or so higher.

[gregvet]

You need more time to see what your "normals" should be. After about 6 months, if my 7.755 kW DC did not produce between 32-45 kWh on a sunny winter day, i would be worried. On rainy days, I'll get maybe 5-10 kWh. Likewise on cloudy days, if I do not see a 7-7.5 kW instantaneous peak value, particularly if I get almost exactly 1/3 or 2/3 of that value, I know I have a faulty string since I have 3 strings. You can see my PV Output here:

http://www.pvoutput.org/list.jsp?userid=28753

[Ian S]

It will continue to go down until February.

Not likely in S. Cali. Probably same as here in Arizona: our worst month is December by far.

[insaneoctane]

... How does it compare to other PVoutput mapped systems near you on a kWh output per installed kW basis ?

I found a 7kW system in a neighboring city (6 mi away) that tracks quite well with my efficiency...Makes me feel more like bad conditions than bad equipment. It's just hard to swallow 488 kWh for a month from a 6kW system in Southern California!

The system is called "Miles Away" if you are familiar with picking comparisons in pvoutput and want to see the data yourself.

For those who asked, I'm in Southern California, zipcode 93021

TNTArray2014.12.05compare.jpg