New 20kW solar roof install seeing low numbers

[bushidosunny]

Hi,

I'm hoping someboday can help me understand if I have a problem or this is expected. I got a 20kW solar panel installed 3 days ago. It is on normal angle roof, no shade system in northen california. For the last two full sunny days I'm only getting peak 8.9 and 7.8 kW. I thought I should see at least 70-80% of the 20kW but maybe theres something I don't understand.

 

[bigblackroof]

For 20kW you have 2 x 7.6kW Tesla Inverters? How are they wired? Did you verify all strings are working by logging directly into the inverter after resetting them? I had 1 string not work at all and they had to come out and take tiles off to find out that someone didnt attach it correctly.

 

[RandyS]

How many solar panels did they install?

 

[bushidosunny]

two inverters i believe. I will check tonight about logging directly into the inverter

 

[bushidosunny]

How many panels did they instView attachment 717473all?

solar roof tiles, not panels

 

[Laketime]

What is a normal roof angle? Are all panels due south?

 

[jjrandorin]

solar roof tiles, not panels

Your thread title says solar roof, but your first post says solar panels, so I was confused as to what you had as well. OP, you did not provide nearly enough information for anyone to give you any sort of real opinion on this, except to say that, if its a solar roof, there is very little chance all the solar roof tiles are facing south (which is the optimum direction).

There is no such thing as a "normal roof angle" either.

There also is no rule about "70 to 80% of installed kW size" or anything. Yearly Production peaked a while ago for time of year, so production is going down, not up. My guess is, there is nothing wrong with your system, but thats just a guess, because we dont have any information other than its a solar roof ( so not all facing the same direction, and likely different roof angles for different roof planes).

 

[bushidosunny]

sorry for my brief discription. I would think that my numbers (40% of stated) were low enough that specifics were not needed. But it is a solar roof. It does not have steep angles, that is what I meant by within normal range, angle of roof is roughly 30 degrees. about 1/3 face east, 2/3 west.

Somewhere on Tesla website says 80% during the summer.

 

[bushidosunny]

the house is actually rotated counter clockwise about 20 degrees.

All help is appreciated.

 

[jjrandorin]

sorry for my brief discription. I would think that my numbers (40% of stated) were low enough that specifics were not needed. But it is a solar roof. It does not have steep angles, that is what I meant by within normal range, angle of roof is roughly 30 degrees. about 1/3 face east, 2/3 west.

Somewhere on Tesla website says 80% during the summer.

So, none of it is southern facing, then? This also isnt summer (summer ended in august, this is october). We dont know what your inverters are, either. Its still my opinion that there is likely nothing wrong.

 

[bushidosunny]

so the inverters would change the production number? they are powerwall plus x 2 .

 

[RandyS]

As a data point about time of year and orientation, I have 41 solar panels that are 300 watts (12.3 kW DC max) with microinverters. Some of the panels are facing south and west and some are not as optimized (kind of like your roof), and my peak generation today in San Diego was 7.2 kW AC just after noon...It is 90 degrees here today with very few clouds...

I think the discussion about your inverters is relevant to see what the max rating is and, therefore, what your inverter(s) will top out at...

 

[bushidosunny]

As a data point about time of year and orientation, I have 41 solar panels that are 300 watts (12.3 kW DC max) with microinverters. Some of the panels are facing south and west and some are not as optimized (kind of like your roof), and my peak generation today in San Diego was 7.2 kW AC just after noon...It is 90 degrees here today with very few clouds...

I think the discussion about your inverters is relevant to see what the max rating is and, therefore, what your inverter(s) will top out at...

Great. thank you for the data point and and inverter information. I see that they can max out and clip. I've also added the orientation of my roof if that helps people. Like everyone, I guess, that buys an expensive item, they want to make sure it is what they paid for.

 

[Big Earl]

It appears that roughly a third of your solar surface faces ENE. Those probably generate very little this time of year. The WSW surfaces will be most productive in the late afternoon but won’t be ideal due to the low sun angle compared to the roof angle. Your numbers don’t seem particularly unreasonable to me. Can you post a graph of your production?

 

[bushidosunny]

It appears that roughly a third of your solar surface faces ENE. Those probably generate very little this time of year. The WSW surfaces will be most productive in the late afternoon but won’t be ideal due to the low sun angle compared to the roof angle. Your numbers don’t seem particularly unreasonable to me. Can you post a graph of your production?

This is my best day

 

[jjrandorin]

You also have the "situation", that because you dont have PTO, your system will scale production to what you can use, and not export anything at all to the utility.

 

[bushidosunny]

You also have the "situation", that because you dont have PTO, your system will scale production to what you can use, and not export anything at all to the utility.

this day i believe did not throttle because the batteries were being charged, and they never reached 100%. The next day when the battery was full it did shut off production to minimum needed.

 

[h2ofun]

Your thread title says solar roof, but your first post says solar panels, so I was confused as to what you had as well. OP, you did not provide nearly enough information for anyone to give you any sort of real opinion on this, except to say that, if its a solar roof, there is very little chance all the solar roof tiles are facing south (which is the optimum direction).

There is no such thing as a "normal roof angle" either.

There also is no rule about "70 to 80% of installed kW size" or anything. Yearly Production peaked a while ago for time of year, so production is going down, not up. My guess is, there is nothing wrong with your system, but thats just a guess, because we dont have any information other than its a solar roof ( so not all facing the same direction, and likely different roof angles for different roof planes).

During the best month like June, with my panels which face s, n, and w, I hit 180kwh in a day. This time of the year I am not down to like 80kwh, and dropping. So no one should expect this time of the year to get anything close to the INVERTERS outputs, no matter what size panels one has. Its the inverter outputs which limit!

 

[BrokerDon]

Here's our 9 month old 15kW DC SunPower / SolarEdge solar output for yesterday on our SoCal office building.

ALL of our solar panels are basically facing south at ~ 10º inclination (ballast mount on our flat roof).

Peak production this week has been averaging 10.3kW

Here's our SolarEdge inverter web portal for our (34) 440W SunPower solar panels if you want more info:

://monitoringpublic.solaredge.com/solaredge-web/p/site/public?name=Ashwill_Associates_Orange_office#/dashboard

 

[bushidosunny]

If this is to be expected for a 20 kw solar roof at my sunny location in northern CA, it is a bit disheartening that it can basically only handle my AC at this time of the year, no EV charging has been done. I "overbuilt" this system, they recommended a 16 kw system.