New Installation with 2 PW+, very low peak and daily solar production.

[jriv]

Hi! I have a recently installed 12.7KW system with two PW+. I’m getting only about 6.2-6.3KW peak production in full sun and the system is producing about 40KWh daily.

I know those numbers are low and I contacted my installer which came to check the installation but couldn’t figure out the issue.

Does anyone have any ideas what may be causing the low values. I have 4 string coming down the roof, two for each inverter.

 

[jjrandorin]

Hi! I have a recently installed 12.7KW system with two PW+. I’m getting only about 6.2-6.3KW peak production in full sun and the system is producing about 40KWh daily.

I know those numbers are low and I contacted my installer which came to check the installation but couldn’t figure out the issue.

Does anyone have any ideas what may be causing the low values. I have 4 string coming down the roof, two for each inverter.

Lets start with a question. Why exactly do you believe that the 6.2 to 6.3 peak production number you are seeing is a "low" value (its not related in the slightest to your 12.7kW system size)?

 

[getakey]

that seems low to me (about 50%) unless the roof placement is really bad. I don't have ideal facing panels and I'm getting almost 80 kWh daily on a slightly smaller system.

 

[jjrandorin]

that seems low to me (about 50%) unless the roof placement is really bad. I don't have ideal facing panels and I'm getting almost 80 kWh daily on a slightly smaller system.

The daily 40kW number sounds a bit low for a 12.7kW system, but we also have had an uptick in people posting the equivalent of:

=======================
"I just got my new system, its [insert system size}, but my peak production is only [insert number]. Shouldnt I be getting peak production of [insert system size]?"
======================

We have no idea why this particular OP is thinking 6.2 / 6.3 is a low number for peak production. We dont know if (for example) because the system is just installed, if daily production being 40kWh is because of the system being limited / curtailed because there is no PTO.

We dont know if they modeled it in PVwatts, or some other modeling tool. We dont know what they were told their annual production is, or what size their inverters are, etc.

Given what we dont know currently, I figured we could start with "why do you believe this number is low"? and perhaps get some of this other information to help this OP.

 

[getakey]

The daily 40kW number sounds a bit low for a 12.7kW system, but we also have had an uptick in people posting the equivalent of:

=======================
"I just got my new system, its [insert system size}, but my peak production is only [insert number]. Shouldnt I be getting peak production of [insert system size]?"
======================

We have no idea why this particular OP is thinking 6.2 / 6.3 is a low number for peak production. We dont know if (for example) because the system is just installed, if daily production is being limited / curtailed because there is no PTO.

We dont know if they modeled it in PVwatts, or some other modeling tool. We dont know what they were told their annual production is, or what size their inverters are, etc.

Given what we dont know currently, I figured we could start with "why do you believe this number is low"? and perhaps get some of this other information to help this OP.

I agree with all you have said and more info would help. That said it seems low

 

[jriv]

The daily 40kW number sounds a bit low for a 12.7kW system, but we also have had an uptick in people posting the equivalent of:

=======================
"I just got my new system, its [insert system size}, but my peak production is only [insert number]. Shouldnt I be getting peak production of [insert system size]?"
======================

We have no idea why this particular OP is thinking 6.2 / 6.3 is a low number for peak production. We dont know if (for example) because the system is just installed, if daily production being 40kWh is because of the system being limited / curtailed because there is no PTO.

We dont know if they modeled it in PVwatts, or some other modeling tool. We dont know what they were told their annual production is, or what size their inverters are, etc.

Given what we dont know currently, I figured we could start with "why do you believe this number is low"? and perhaps get some of this other information to help this OP.

Hello! I have 26 panels facing south, I am located in PR where we get an average of 5.5 hours of full sun daily. Considering those fact, a 12.7kw system shouldn’t have a peak of about 6KW daily, let alone less than 50KWh of daily production. My father have a system installed more than 10 years ago, a 6.5KW system with a 7KW SMS inverter and he gets over 35kwh of power produced daily.

My brother has a 8KW system that constantly peaks at over 7KW and generates over 45-50kWh daily.

We don’t have to wait for PTO here, as soon as the system is installed and commissioned it is connected to the grid. You do know the inverters size as I clearly stated that it was a two PW+ system so I have two 7.6kw inverters.


In most scenarios a 12.7KW running at less than 50% it’s capacity would be considered low. If you take into account the info offered above, I would consider it to be VERY low.

The installer offered me a 11.2KW system to cover my daily usage and I decided to oversize it a bit to cover a future increase in consumption so something is definitely wrong with it.

 

[h2ofun]

Hello! I have 26 panels facing south, I am located in PR where we get an average of 5.5 hours of full sun daily. Considering those fact, a 12.7kw system shouldn’t have a peak of about 6KW daily, let alone less than 50KWh of daily production. My father have a system installed more than 10 years ago, a 6.5KW system with a 7KW SMS inverter and he gets over 35kwh of power produced daily.

My brother has a 8KW system that constantly peaks at over 7KW and generates over 45-50kWh daily.

We don’t have to wait for PTO here, as soon as the system is installed and commissioned it is connected to the grid. You do know the inverters size as I clearly stated that it was a two PW+ system so I have two 7.6kw inverters.


In most scenarios a 12.7KW running at less than 50% it’s capacity would be considered low. If you take into account the info offered above, I would consider it to be VERY low.

The installer offered me a 11.2KW system to cover my daily usage and I decided to oversize it a bit to cover a future increase in consumption so something is definitely wrong with it.

If you inverter is 7.6K, thats all you would get.

 

[jriv]

If you inverter is 7.6K, thats all you would get.

Yeah, if I had one but I have two. Even if I had one, with a 12.7 system I would expect it to be clipping at 7.6 for good amount of time daily and it is not even getting close to that.

 

[getakey]

If you inverter is 7.6K, thats all you would get.

he has 2 of them

 

[getakey]

Yeah, if I had one but I have two. Even if I had one, with a 12.7 system I would expect it to be clipping at 7.6 for good amount of time daily and it is not even getting close to that.

maybe the installer only hooked up 1 string to each inverter or 1 inverter isn't working

 

[jriv]

maybe the installer only hooked up 1 string to each inverter or 1 inverter isn't working

Both inverters are working, they are coming back tomorrow to check the connections in the roof but both inverter show both strings working correctly with the same voltages.

I have 4 totals strings, two to each inverter.

 

[jjrandorin]

Hello! I have 26 panels facing south, I am located in PR where we get an average of 5.5 hours of full sun daily. Considering those fact, a 12.7kw system shouldn’t have a peak of about 6KW daily, let alone less than 50KWh of daily production. My father have a system installed more than 10 years ago, a 6.5KW system with a 7KW SMS inverter and he gets over 35kwh of power produced daily.

My brother has a 8KW system that constantly peaks at over 7KW and generates over 45-50kWh daily.

We don’t have to wait for PTO here, as soon as the system is installed and commissioned it is connected to the grid. You do know the inverters size as I clearly stated that it was a two PW+ system so I have two 7.6kw inverters.


In most scenarios a 12.7KW running at less than 50% it’s capacity would be considered low. If you take into account the info offered above, I would consider it to be VERY low.

The installer offered me a 11.2KW system to cover my daily usage and I decided to oversize it a bit to cover a future increase in consumption so something is definitely wrong with it.

No, we didnt know the system size because powerwall+ can have 2 different inverter sizes, and while I have no idea what peak production would be on your system, in normal cases it would NOT be anywhere near "12.7". In fact, I would be very surprised if you actually have (2) 7.6 inverters (because tesla also has a 3.8 inverter size for the Powerwall+ and for a system size of 12.7 they would likely use a 7.6 and a 3.8).

it would be HIGHLY unlikely for someone to have 15kW of inverter capacity with a 12.7kW system.

With all that being said, the 40kW daily number would be the more concerning one, especially if everything is facing south. Since you state you dont require any sort of PTO there, perhaps your system is mis configured for curtailment?

 

[jriv]

No, we didnt know the system size because powerwall+ can have 2 different inverter sizes, and while I have no idea what peak production would be on your system, in normal cases it would NOT be anywhere near "12.7". In fact, I would be very surprised if you actually have (2) 7.6 inverters (because tesla also has a 3.8 inverter size for the Powerwall+ and for a system size of 12.7 they would likely use a 7.6 and a 3.8).

it would be HIGHLY unlikely for someone to have 15kW of inverter capacity with a 12.7kW system.

With all that being said, the 40kW daily number would be the more concerning one, especially if everything is facing south. Since you state you dont require any sort of PTO there, perhaps your system is mis configured for curtailment?

I do have two 7.6 inverters since that was a requirement I had. I will be expanding the system over time above 15kw so I wanted to have the capacity in place. No, the system is not mis configured since I do see it exporting energy to the grid if I don’t use it.

I do have some concerns about the wiring since both inverters are wired as “four combined strings” as indicated in the supported DC wiring configurations. However I don’t have four combined strings, I just have two independent strings coming down to each inverter.

Maybe someone familiar with Tesla inverter wiring can tell me if wiring two independent strings as indicated in the “four combined strings” diagram can cause any reduction in power production?

 

[yblaser]

I do have two 7.6 inverters since that was a requirement I had. I will be expanding the system over time above 15kw so I wanted to have the capacity in place. No, the system is not mis configured since I do see it exporting energy to the grid if I don’t use it.

I do have some concerns about the wiring since both inverters are wired as “four combined strings” as indicated in the supported DC wiring configurations. However I don’t have four combined strings, I just have two independent strings coming down to each inverter.

Maybe someone familiar with Tesla inverter wiring can tell me if wiring two independent strings as indicated in the “four combined strings” diagram can cause any reduction in power production?

Are you sure they didn't wire two strings in parallel on the roof and then run down one set of wires for the two parallel strings. If they did this then it would be correct to jumper the inverter inputs.

I don't think we will be much help without your design plans and the sting level voltage and current readings. Otherwise we are just throwing out random guesses.

 

[jriv]

Hello! Just letting everyone one know that the issue has been fixed. There were two problems limiting the system performance.

One inverter was producing perfectly fine but the other was running at 20-30% its expected capacity.

There where problems in both strings coming down to that inverter.

First, one string was completely disconnected since it was mistakenly left disconnected in the combiner box, as soon as that was fixed, production jumped to about 8.5 to 9KW. That was at 10AM.

However, production was still lower than expected since we were expecting over 10KW.

After further analyzing the other strings that was reporting crazy fluctuations in voltage, the installer isolated the problem shutting down the whole string to a single panel with a defective MC4 connector.

They replaced it and as soon as the inverter recognized that string voltage within operational parameters the production jumped to 12.7KW!!

It stayed at 10-12KW up until 2PM when it started to come down.

It is now almost 3:30PM and the system has generated over 42KWh while being down most of the morning for troubleshooting FYI, 42KWh was the highest production I had recorded before in a very nice and sunny day.

Looking forward to seeing the full day results this coming days!

Thanks everyone for their help
and suggestions!

 

[jriv]

Are you sure they didn't wire two strings in parallel on the roof and then run down one set of wires for the two parallel strings. If they did this then it would be correct to jumper the inverter inputs.

I don't think we will be much help without your design plans and the sting level voltage and current readings. Otherwise we are just throwing out random guesses.

They didn’t, they are using higher wattage panels (490W) instead of the Tesla branded ones. Since it is only two strings, they jump them to avoid running into voltages that are two high without having to pay much attention to strings sizes. If they had more than two “independent strings” they have to keep in mind string size much more closely.

 

[yblaser]

They didn’t, they are using higher wattage panels (490W) instead of the Tesla branded ones. Since it is only two strings, they jump them to avoid running into voltages that are two high without having to pay much attention to strings sizes. If they had more than two “independent strings” they have to keep in mind string size much more closely.

Glad it seems to be working now. Jumpering the two MPPT inputs only reduces the input current to each MPPT it does not affect the voltage.

 

[jriv]

Glad it seems to be working now. Jumpering the two MPPT inputs only reduces the input current to each MPPT it does not affect the voltage.

Got it! I stand corrected! That’s what the meant, they don’t have to worry as much about it if they combined the strings in parallel or not, either way they jump them.

I’m sure in more complex installs strings sizes and combinations become much more relevant but for many small/medium residential applications they aren’t as relevant.

 

[jriv]

Quick update!

Today was my first full day with the system fully working.

This build is insane! We had a fairly cloudy day, you can see the many ups and downs in the graph, however the system managed to produce 72kWh and peaks as high as 14.4kW.

Very impressed so far!

 

[GoTzillaR]

isnt the peak 12.9kW?