Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register
  • The final cut of the 8th episode of the Tesla Motors Club Podcast, featuring Balazs Biro, of the prominent Hungarian EV channel Villanyautósok, is now available. You can watch it now on YouTube or listen to it on all major podcast networks.

Why is our solar production getting cut off?

jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
6,512
4,454
Northern California
Hi,

I was looking at the graphs for our SolarRoof's production and noticed that the top is getting cut off. The roof has a total rating of 12.75 kW and the South facing portion is 8 kW. Both the north and south-facing roof planes are in complete sunlight. I have verified there is no shading on any part of the roof during the period in question. Any thoughts?

Here is the graph from yesterday which was sunny from 7-ish AM on.

Solar-with-cutoff.jpg
 
Looking at your curve it appears you had some high cloud cover throughout the day, which is why your graph isn't smooth. High clouds will limit solar when blocking the sun, but also enhance solar when the sun is on the edge of the clouds. High clouds can also cause solar to begin sooner in the morning and end later in the evening as they can act as a mirror. At the same time since solar is very limited early morning, they can also completely block solar production during the beginning of your usual solar production if they are completely blocking the sun
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
14,197
17,923
Riverside Co. CA
Im not an expert on this (not even close) but it sounds like you are not being inverter limited. I find the shape of the solar production chart somewhat interesting, but I wonder if its because its solar roof. I know in my own solar panel installation, its 8.7kW sized, and my inverters are 4.2 and 3.4, yet I have never seen higher than about 6.3kW peak production at any given time, given that my panels are facing in different directions.

Thing is, for a system that size (and I remember you have some trees) that production number looks low to me for this time of year. Low like something is not reporting. I have no shading, and am in southern cali not norcal, but on a fully sunny day right now my 8.7kW system is producing about 47kWh (Saturday april 10th,) 46 kWh (Friday April 9th).

For a system that much larger than mine to have production like that looks low to me.
 
  • Like
Reactions: mswlogo

getakey

Active Member
Jan 28, 2020
1,737
630
95762
I have an 11.8 kW system on east and west facing roof. Here's my production for what I think is the same day in Sacramento area. There were some scattered high light clouds during the day. Seems like you have some heavy shading in the afternoon. Not sure if that totally explains your lower production.
 

Attachments

  • Screenshot_20210413-092343.png
    Screenshot_20210413-092343.png
    172.4 KB · Views: 38
  • Informative
Reactions: jjrandorin

jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
6,512
4,454
Northern California
I have an 11.8 kW system on east and west facing roof. Here's my production for what I think is the same day in Sacramento area. There were some scattered high light clouds during the day. Seems like you have some heavy shading in the afternoon. Not sure if that totally explains your lower production.
No shading. That was my first thought. I went out and checked at 11, 12, 1, and 2 and the roof is completely unshaded and in full sunlight.

I was expecting the graph to look similar to yours and the difference was the reason I posted this question. I am in the Livermore-Pleasanton area, so our weather is not dramatically different than yours

Also, this flattening of the curve seems fixed at the 6 kW value. It has now occurred at this same value for 5 consecutive days. It is 10:45 AM now. We will hit 6 kW by11:10 and I expect the flattening will start. I wonder if one of the strings of active SolarRoof tiles is dead or one of the shutdown (not correct name) blocks is kicking in at higher current/voltages.
 
Last edited:

jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
6,512
4,454
Northern California
I see 2 issues - the flattening and the virtually zero production after 4 pm. The lack of production after 4 is why I thought you had shading
I see. Yes in the afternoon we have shading. We have trees to the West that start cutting off production after 4 or so this time of year. They are on our property, so I could get them cut. But, as we get further toward summer the sun is high enough to hit the roof even in the late afternoon. But then there is the 1,000-foot hill to West that cuts off the sun. No getting around the hill. So that shading I can understand. But, this flattening is what is bothering me.
 

h2ofun

Active Member
Aug 11, 2020
3,608
867
auburn, ca
I see. Yes in the afternoon we have shading. We have trees to the West that start cutting off production after 4 or so this time of year. They are on our property, so I could get them cut. But, as we get further toward summer the sun is high enough to hit the roof even in the late afternoon. But then there is the 1,000-foot hill to West that cuts off the sun. No getting around the hill. So that shading I can understand. But, this flattening is what is bothering me.
Whats wrong with the flattening? I am up in Auburn, and I see this on my setup.
 

jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
6,512
4,454
Northern California
Whats wrong with the flattening? I am up in Auburn, and I see this on my setup.
To me, this implies that my system has maxed out in terms of its ability to convert sunlight to electricity. That area of the roof is listed at 8 kW and if it got to 8 kW and then flattened I would understand. However, we are flattening at 6 kW.

Perhaps I am expecting too much. Do your panel's production flatten at a constant 75-80% of their rating this time of the year?
 

h2ofun

Active Member
Aug 11, 2020
3,608
867
auburn, ca
To me, this implies that my system has maxed out in terms of its ability to convert sunlight to electricity. That area of the roof is listed at 8 kW and if it got to 8 kW and then flattened I would understand. However, we are flattening at 6 kW.

Perhaps I am expecting too much. Do your panel's production flatten at a constant 75-80% of their rating this time of the year?
My system rated 14.7 to 15K. Most I have ever ever gotten, and not ever often, is 11.9K, and this is under perfect solar conditions
 

MorrisonHiker

Well-Known Member
Moderator
Mar 8, 2015
10,546
10,569
Colorado
Can you tell if the M-4 inverter is working properly or if all strings are functional?

My system rated 14.7 to 15K. Most I have ever ever gotten, and not ever often, is 11.9K, and this is under perfect solar conditions
Do your panels face multiple directions? Our 20.5 kW system has panels facing four different directions. At this time of the year, the system peaks around solar noon at just over 17 kW but yesterday we had intermittent clouds and sometimes hit 22 kW.
 

h2ofun

Active Member
Aug 11, 2020
3,608
867
auburn, ca
Can you tell if the M-4 inverter is working properly or if all strings are functional?


Do your panels face multiple directions? Our 20.5 kW system has panels facing four different directions. At this time of the year, the system peaks around solar noon at just over 17 kW but yesterday we had intermittent clouds and sometimes hit 22 kW.
2/3 face south, 1/3 face west but only get sun in afternoon. The 2/3 gets lots of shading from neighbors trees in morning.
 

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top