Performance warranty for Solar Panel

[solar_newbie]

Hi All,

How do you know if your solar panels keep up the performance? How to claim performance warranty (assume Solar panel is up and running)?

[inetdog]

Hi All,

How do you know if your solar panels keep up the performance? How to claim performance warranty (assume Solar panel is up and running)?

Monitoring software archiving the statistics collected by the inverter itself.
Or use of a separate production meter if SRECs or similar are used in your area.

[Naptown]

Actuslly there is no way to tell in the field. Unless it falls off a cliff.
To make a claim usually means shipping back to msnufacturer ( at your expense) they test under STC conditions say yes or no snd send your panel back or a replacement. Again you pay on the wsy back.
Read the warranty.

[sensij]

How do you know if your solar panels keep up the performance?

Best way I can think of is to compare your output to other nearby systems of similar orientation on PVoutput.org. If you are finding significant differences, that would be motivation for the next level of electrical testing to try to confirm the problem, and ultimately, RTV for their calibrated testing.

[inetdog]

solar_newbie,
There is a distinction between performance tracking (or initial confirmation on new panels) versus the system performance guarantee (usually worthless) from the installer. Which are you asking about?

[bcroe]

How do you know if your solar panels keep up the performance?

I tell by having 2 identical systems. A glance at the power should show a match any time
no shading is involved. Otherwise, I am running out with my clamp on ammeter. Bruce Roe

[J.P.M.]

As Naptown and others write, there is not much you can do in a practical way to verify performance for a warranty claim on your own.

Without a reliable way to simultaneously measure input and output you're mostly S.O.L. It can be done with a pyranometer and other instrumentation and conversion to P.O.A. irradiance and system output monitoring, but the # of variables involved, the limits on instrument accuracy, horiz. to P.O.A. irradiance conversion uncertainty and other things all probably have more variability than the usually small and variable differences necessary to determine most performance degradation.

I do it all the time and about the best I can claim is very roughly about +/- 0.75% accuracy on a continuing basis. There are a lot of variables to consider.

[solar_newbie]

solar_newbie,
There is a distinction between performance tracking (or initial confirmation on new panels) versus the system performance guarantee (usually worthless) from the installer. Which are you asking about?

I am looking on the following warranty on solar vendor :
- Year 1 : product at least 97%
- Year 2 - 25 : drop max 0.7% per year.

First, where I can make sure each single panel product 97% based on what calculation ?
Second, Assume I got the baseline for year 1 (which is not sure based on question 1), how can I enforce year 2 and above to have performance drop less than 0.7%

Assume I suspect performance drop 2% ? How can I prove it and what do I need to have to prove it?

PS: I got the answer to identify which panel is not good vs the rest in the same array based on on my enphase inverter. I guess people which Solaredge can know the production of each single panel, but not people with String Inverter only.

[bcroe]

I am looking on the following warranty on solar vendor :
- Year 1 : product at least 97%
- Year 2 - 25 : drop max 0.7% per year.

First, where I can make sure each single panel product 97% based on what calculation ?
Second, Assume I got the baseline for year 1 (which is not sure based on question 1), how can I enforce year 2 and above to have performance drop less than 0.7%

Assume I suspect performance drop 2% ? How can I prove it and what do I need to have to prove it?

PS: I got the answer to identify which panel is not good vs the rest in the same array based on on my enphase inverter. I guess people which Solaredge can know the production of each single panel, but not people with String Inverter only.

As a practical matter, I would not worry about a 2% drop. That would hardly matter in this
picture. Maybe after 10 years I'd expect something measurable. What you need to worry
about now is something severly degrading or quitting completely; not too hard to detect.

A weak panel will have low voltage compared to the rest of a string. Bruce Roe

[solar_newbie]

As a practical matter, I would not worry about a 2% drop. That would hardly matter in this
picture. Maybe after 10 years I'd expect something measurable. What you need to worry
about now is something severly degrading or quitting completely; not too hard to detect.

A weak panel will have low voltage compared to the rest of a string. Bruce Roe

If there is no way to do performance warranty. What is the point to have it?
2% is too small to notice but 4-5% perhaps.
If I layout all panels next to each other and provide the output for each of them. If one shows 5% lower, I should know after 1 year right ? Enough evident to do performance warranty claims ?

[skipro3]

Here is my Solaredge monitoring portal where I charted panel #3 and panel #10 of a 16 panel system. These are the top and bottom performers. As you can see, there is a reading of watts at the high point of the day 9/19/15. The difference between the highest and lowest panel in my system here is 6%. I can go back to any date since the panels were installed and compare. So from year to year, I can see if there are changes on individual panels and between panels.


There is morning shading at this time of year, to explain the graphs early day anomalies.



My Solaredge monitoring portal will also allow me to set alarm points and send me a text or e-mail if those alarms are triggered.

[J.P.M.]

If there is no way to do performance warranty. What is the point to have it?
2% is too small to notice but 4-5% perhaps.
If I layout all panels next to each other and provide the output for each of them. If one shows 5% lower, I should know after 1 year right ? Enough evident to do performance warranty claims ?

1.) The point of a performance warranty is as a marketing tool. Otherwise, they're pretty much useless.

2.) Many/Most warranties have a stated 1st year burn in degradation. 3 - 5% is common.

3.) Keep good records. Including a record of all the panel temps (good luck on that one). Wind and relative location can affect panel temps. and thus efficiency. Also, many panels are conservatively rated so their output will sometimes initially exceed stated output. Also, keep a record of when and how you clean the panels.

Bottom line: There is probably no practical way to verify a performance warranty claim in situ. The bright side is that most equipment is (probably) slightly conservatively rated and doesn't break down all that much.