Enphase REC Alpha solar output/generation

[jplee3]

Hey all,

I just had an array of 19 REC Alphas installed on our roof. One of the panels is consistently performing as much as 200-300+ watts less than the rest. I have contacted Enphase about this and they tried reflashing the firmware/resetting the microinverters. I called our installer and he took a look at the install and pictures again and is saying that there are a couple flue vents that are likely casting a small shadow onto the grid next to it. Even with a small shadow, it can impact the panel's production:

20221109_152040.jpg

They put that split in the panels at the top to provision for it since I guess it was in the way, but apparently they couldn't position that one panel to fully avoid the shadow of the vent and now, per the installer, that appears to be impacting the total output. This feels like one of those instances where "it is what it is" and there's not much I can do about it. He checked the inverter output and it looks fine in comparison with the other inverters. The panel health also appears "normal"

I guess the only other option would be to reposition that vent or cut it lower hahaha... not sure that's even possible. I guess I'll just have to forfeit the potential 200-300watts of loss in production each day then :T

[J.P.M.]

Panels that get any significant shade will have their output reduced, often/usually more than the shaded area would lead one to believe.
Too bad you didn't know that before you had the array done.
As it looks like the top edge of the array is close to the roof peak, depending on array azimuth, one way to perhaps have reduced the shading penalty would have been to move the entire array closer to the lower edge of the roof. Again, depending on array azimuth, that would have shifted the shading times and also most likely have reduced the amount of energy lost to shading.
But the way it is now, and the way the install was done, unless you want to spend some $$, you're probably stuck with it.
Are any other panels affected so far ? You'll probably see more or at least different loss patterns as the solar angles change with the seasons, again, depending on array azimuth.

BTW, how did you get away with placing your array so close to the roof peak ? What, if anything did the AHJ inspector have to say it ?
Also, and because I can't make it out from the picture, did you wind up replacing the under-array tiles with comp. shingles ?

Add: What's the array's azimuth ? What date and time of day was the photo taken ?

[jplee3]

Panels that get any significant shade will have their output reduced, often/usually more than the shaded area would lead one to believe.
Too bad you didn't know that before you had the array done.
As it looks like the top edge of the array is close to the roof peak, depending on array azimuth, one way to perhaps have reduced the shading penalty would have been to move the entire array closer to the lower edge of the roof. Again, depending on array azimuth, that would have shifted the shading times and also most likely have reduced the amount of energy lost to shading.
But the way it is now, and the way the install was done, unless you want to spend some $$, you're probably stuck with it.
Are any other panels affected so far ? You'll probably see more or at least different loss patterns as the solar angles change with the seasons, again, depending on array azimuth.

BTW, how did you get away with placing your array so close to the roof peak ? What, if anything did the AHJ inspector have to say it ?
Also, and because I can't make it out from the picture, did you wind up replacing the under-array tiles with comp. shingles ?

Add: What's the array's azimuth ? What date and time of day was the photo taken ?

Yea it would have been nice if the company doing the install would have called this out - multiple times through the planning process, I called out that there are several vents/tee-tops on the roof and pointed out the locations but they seemed to make little of it. The day of the install they told me they had to arrange the panels slightly differently because of one of the positions of the vents (duh, I told you guys about all this before and it's pretty obvious they're there when you're looking at the house even from the street). Considering they do installs pretty regularly I would think its kind of a big deal to overlook something like this but maybe this kind of installation faux paus is more common than we know?

The vent sticking out up there is prpbably about a foot or so high. It looks like there may be a set of them and they're either 3 or 4 inches, so possibly 8-10" across? Considering how close in proximity these appear to be to the panels around them, i guess its not inconceivable that a shadow would be cast across them at some point from the pipe. I'm just not sure how to quantify how many watts lost should be expected. And I'm not sure how significant the loss is that I described as well (200-300w per day seems to be a lot if you add it up over the course of a year... that's like 109kw... but in the grand scheme of things our system is sized at 7.6.kw and 12,236 kWh of output per year so 109kwh is less than 1% variance it seems? Guess I'll have to keep monitoring. If it becomes significantly less, I'm not sure if there is any recourse (outside of threatening/taking legal action possibly... it seems like it wouldn't be significant enough to get to that point though)

Not sure regarding the panels being close to the roof peak or what anyone said. Everything was taken care of by the company we had install the panels. They submitted all the plans and met with the inspectors and there were no notable hiccups per what I heard. From what I can see, I think there's maybe around 3-4' of space to the ridgeline from where the top of the panels are up there. The angle of the picture might be deceiving because that roof is quite steep.

We did the panel over tile process (no comp-out).

The azimuth is 250. I took that picture today 11/9 at 3:20pm

BTW: this is today's output:
image_15292.jpg

This one from October 24th shows even more disparity:
image (16).jpg



UPDATE: Here's a better photo of the roof showing the vents and I think I see a small shadow cast in the very upper-right hand corner of the panel to the left of the vents (this is the panel with limited output/production):

[jplee3]

Yea, so it looks like the vents are the culprit then: pics taken around it's 11/10 @ 9:07am PST

Had I realized this or had it been pointed out, I probably would have gone with 18 panels :T

[J.P.M.]

Yea, so it looks like the vents are the culprit then: pics taken around it's 11/10 @ 9:07am PST

Had I realized this or had it been pointed out, I probably would have gone with 18 panels :T

Thanx for the info and the pics.
So, for the two days where you're showing output, it looks like you're losing ~ 10 - 20 % of that panel's output in the fall and I'd think a bit less as a %age of annual output for that panel over an entire year.
Without knowing more, I'd SWAG you'll lose about 75 - 100 kWh/yr. from that vent shading.
You could move the panel but given that the roof is pretty packed already, it looks like there's not too many options in that respect. Anyway, I doubt it would be worth the time and expense for the relatively small gain in annual output you might see.

[jplee3]

Thanx for the info and the pics.
So, for the two days where you're showing output, it looks like you're losing ~ 10 - 20 % of that panel's output in the fall and I'd think a bit less as a %age of annual output for that panel over an entire year.
Without knowing more, I'd SWAG you'll lose about 75 - 100 kWh/yr. from that vent shading.
You could move the panel but given that the roof is pretty packed already, it looks like there's not too many options in that respect. Anyway, I doubt it would be worth the time and expense for the relatively small gain in annual output you might see.

Here's one more from today (currently 1:53pm) and it's even more drastic: image (17).jpg

Just went outside to check for shadows and there are none although, I realize this image is representative of the *cumulative* kwh per day. I really wish they had a view that showed by the hour or even within the hour by 15-30min increments. It would be way more useful/helpful but I imagine most people probably don't care as much.


The problem with our stupid roof is that as soon as you start walking on those tiles, they start breaking. So it all adds to the expense on top of whatever you intend on doing up there.

[J.P.M.]

Here's one more from today (currently 1:53pm) and it's even more drastic: image (17).jpg

Just went outside to check for shadows and there are none although, I realize this image is representative of the *cumulative* kwh per day. I really wish they had a view that showed by the hour or even within the hour by 15-30min increments. It would be way more useful/helpful but I imagine most people probably don't care as much.


The problem with our stupid roof is that as soon as you start walking on those tiles, they start breaking. So it all adds to the expense on top of whatever you intend on doing up there.

I've got a string inverter system and never saw a need for panel level monitoring anyway. Seems too much complication and more chance for stuff to go wrong, but I watch my system like the hawks that sit on my roof.

That's what happens when rushed and why a lot of PV peddlers say installing over mission tile is impossible. I've watched installs on ~ 12 mission tile roofs in my HOA with some but very little breakage. Walking in flat concrete tiles is easier but still needs focus while walking on them. Clay mission tiles same, just more care.
I've learned to walk on both and used 2ft. X 2ft. X 3/4" CDX to spread the load on clay tiles early on, but after practice and care I can walk on either without the CDX. It just takes a system and knowledge of where and how to step. It's a bit of an art that good roofers know.