Solar roof production before PTO vs after PTO

[uscpsycho]

Hello, this is my first post here after discovering this forum. Looks like lots of super knowledgeable members!

My solar roof is finally ready for PTO and Tesla is trying to get me to pay my invoice before activating. But I have some concerns and want them resolved before I pay or I may never get them to address the (possible) issues after I've paid.

If you read nothing else, my main question is if it is normal for my solar production to be below full capacity before PTO and if it will go up after PTO?

So, there are two main issues. The first is that I am supposed to be able to peak at 11.3 kW of production but in my extensive checking of the app (I've been in self consumption mode since December) I don't think I've ever seen it hit 9, even when it's 100 degrees outside and there's not a cloud in sight. That being said, there might be a handful of times when it went over. I frequently check the current live production but when I go into the historical charts, sometimes I see something like the attached screenshot. Is this chart telling me that on this day I hit 10.3 kW at some point? That would be surprising because on this particular day the high was only 77. If that is what this chart is telling me then this day is definitely an outlier.


Anyway, I told Tesla that I don't think I'm producing as much electricity as I should be but they say that I won't be at full production capacity until after PTO. Is it true that Tesla throttles the system before PTO? That doesn't make a whole lot of sense to me, but if this is true then there is no issue here.

The other issue is that there are times when I am pulling power from the grid well before I hit the powerwall reserve cutoff. I have it set at 10% and most days this is respected and I only pull power from the grid when I drop to 10% reserve. But on other days, and I've noticed this seems to happen on overcast days, I can start pulling power from the grid well before I hit 10%. I'm not talking a lot of power here, it's 1-1.5 kWh but on these days it takes me from 100% solar to as low as 96% solar. Day after day that adds up. Does this suggest there is a problem or is this ever normal? Could it have anything to do with not having PTO? Here's what the app is showing me, you can see my reserve doesn't get close to 10%


Thanks in advance for any insights!

 

[arnolddeleon]

If you read nothing else, my main question is if it is normal for my solar production to be below full capacity before PTO and if it will go up after PTO?

Yes. Tesla will try to prevent your system from exporting before PTO.

If I have more time I will try to answer your other questions but I'm hoping others will be beat me to them.

 

[Redhill_qik]

The first is that I am supposed to be able to peak at 11.3 kW of production

What are you basing this on? The amount of solar roof panels? The inverter size? PVwatts estimates for your system components, orientation and geo location?

 

[uscpsycho]

Yes. Tesla will try to prevent your system from exporting before PTO.

If I have more time I will try to answer your other questions but I'm hoping others will be beat me to them.

Just to clarify, I am seeing this even when my Powerwalls are well below 100% and I have plenty of storage. So limiting my production in that situation doesn't affect exporting. When my batteries are at 100% my production immediately drops to 0.

 

[jjrandorin]

Just to clarify, I am seeing this even when my Powerwalls are well below 100% and I have plenty of storage. So limiting my production in that situation doesn't affect exporting. When my batteries are at 100% my production immediately drops to 0.

The actual operative question is the one from @Redhill_qik . On "what exactly" are you basing "I am supposed to be able to peak at 11.3 of production" on (note, if its because "My installed system size is 11.3" then your assumption is probably incorrect).

 

[nyprepper]

@uscpsycho you will never see peak production on a hot 100 degree day. my system will only reach peak if it is less than 75f outside.

another variable I didn't see you mention is your inverter's rating which could be a limiting factor

 

[uscpsycho]

What are you basing this on? The amount of solar roof panels? The inverter size? PVwatts estimates for your system components, orientation and geo location?

I *was* basing this on what the Tesla employee who was here at my inspection told me a few weeks ago. He said that I should be able to generate 11.3 kW.

But perhaps this was wrong. Looking at a previous email exchange with Tesla I found this "we installed 158 SR tiles at 72 watts a tile, 158 x 72 = 11,376. Divide 11,376 by 1000 and you get 11.376, which is the DC system size. The CEC rating factors in the inverters conversion efficiency which will not be 100%, hence why the AC rating is slightly lower than the DC rating." I was inquiring about why an email from my electric company said "Size: 10.0 kW AC-CEC" and that was Tesla's response. So I suppose this means that I should not expect to see more than 10.0 kW?

Still, as I said before, I regularly check the system at all times of day and in all kinds of weather and I am maxing in the low to mid 8 kW range. There are a few very rare outliers when it is higher. If I scroll back far enough in the app I can see one day when I hit 10 kW and two or three days when I touched the 9's. But then why are these just very rare blips?

It doesn't look like much fun, but would it be worthwhile to dig deeper using pypowerwall? Or post photos of my wiring or post my schematics? I didn't want to post a deluge of info unless that info would be useful.

@uscpsycho you will never see peak production on a hot 100 degree day. my system will only reach peak if it is less than 75f outside.

another variable I didn't see you mention is your inverter's rating which could be a limiting factor

Why is peak production highest in the 70's? Is that normal or is this a quirk for you due to the direction your panels face or something like that?

I have two Powerwall+ inverters so that's two 7.6 inverters. I don't think this is a limiting factor. Even if I was producing at 11.3 I would not be tapped out.

 

[uscpsycho]

The truly pressing question is if there is any truth to Tesla telling me that my peak production will increase after PTO? It makes sense that my production is capped if my batteries are at 100% (I have one PW and two PW+) because I can't export. But if my batteries are at 50% is it possible that my production is limited and will be higher after I have PTO? Or is what I am getting now the same as it will be after PTO?

If what Tesla tells me is in fact true then that means they throttle customers' production before PTO. So how much do they throttle and what kind of increase in peak production will I see after PTO?

 

[nyprepper]

@uscpsycho It has to do with the ambient temperature. The panels lose efficiency at higher temps. I have a 6.6kw array and a 7.6kw inverter. In full sun with low 70's outdoor temp I've seen my production as high as 7.2kw. On very hot summer days in full sun I will only typically see 5.8-6.2kw.

 

[nyprepper]

The truly pressing question is if there is any truth to Tesla telling me that my peak production will increase after PTO? It makes sense that my production is capped if my batteries are at 100% (I have one PW and two PW+) because I can't export. But if my batteries are at 50% is it possible that my production is limited and will be higher after I have PTO? Or is what I am getting now the same as it will be after PTO?

If what Tesla tells me is in fact true then that means they throttle customers' production before PTO. So how much do they throttle and what kind of increase in peak production will I see after PTO?

I think you might be misunderstanding what they are saying. I'm assuming that if you do not have PTO you are not feeding to the grid. If that is the case, keep in mind the energy you are generating from solar needs somewhere to go. If your batteries are fully charged and your solar is generating more than the house is drawing, then your inverters will temporarily shutdown. This would limit your overall daily production. Maybe this is what Tesla means when they say your output will increase after PTO? Maybe they mean "total daily output/production" versus point-in-time peak output.

 

[jjrandorin]

The truly pressing question is if there is any truth to Tesla telling me that my peak production will increase after PTO? It makes sense that my production is capped if my batteries are at 100% (I have one PW and two PW+) because I can't export. But if my batteries are at 50% is it possible that my production is limited and will be higher after I have PTO? Or is what I am getting now the same as it will be after PTO?

If what Tesla tells me is in fact true then that means they throttle customers' production before PTO. So how much do they throttle and what kind of increase in peak production will I see after PTO?

You are talking about two separate things.

1. What is the peak production I will see at any one time?

You will not see peak production of your DC system size at any one time, unless your system is ground mounted, pointed at the optimum angle, and on a specific time of day (or your system is ground mounted and tracks the sun). So, you will not see DC system size as your max peak production, nor should you care about that as production should be measured in weeks / months, not "peak inrush power at any specific time:"

2. Is it possible for my production to increase after pto on a tesla system?

Yes, since some systems with powerwall+ are put in a "self consumption only" mode, which means that the system curtains the solar production since pre PTO you can not back feed the grid. You may see increased production (daily production) after PTO, if your system is in this self consumption mode.

Note that for many of us prior to this, we were not able to (by policy anyway) turn our systems on AT ALL prior to permission to operate (PTO) as there was no "self consumption only" mode. It is entirely possible that you see increased DAILY production after PTO, but not increased PEAK production as a system size of X does not in any way, shape or form dictate what PEAK production is.


Here is just one (of a few) different threads here where people ask "I bought a system that was X size, I dont get X peak production, I was misled"

Solar Panels only generating about 60% [of peak production number]

I had 11.6 kW of solar panels and 3 Powerwalls installed about a month ago here in Miami, FL. It's summer so the days are pretty long, and even on the clearest day, I seem to only generate about 7.0 or 7.5 kW of power from the solar panels. Anyone else having this experience? I feel like I...

teslamotorsclub.com

 

[Redhill_qik]

I *was* basing this on what the Tesla employee who was here at my inspection told me a few weeks ago. He said that I should be able to generate 11.3 kW.

But perhaps this was wrong. Looking at a previous email exchange with Tesla I found this "we installed 158 SR tiles at 72 watts a tile, 158 x 72 = 11,376. Divide 11,376 by 1000 and you get 11.376, which is the DC system size. The CEC rating factors in the inverters conversion efficiency which will not be 100%, hence why the AC rating is slightly lower than the DC rating." I was inquiring about why an email from my electric company said "Size: 10.0 kW AC-CEC" and that was Tesla's response. So I suppose this means that I should not expect to see more than 10.0 kW?

Still, as I said before, I regularly check the system at all times of day and in all kinds of weather and I am maxing in the low to mid 8 kW range. There are a few very rare outliers when it is higher. If I scroll back far enough in the app I can see one day when I hit 10 kW and two or three days when I touched the 9's. But then why are these just very rare blips?

It doesn't look like much fun, but would it be worthwhile to dig deeper using pypowerwall? Or post photos of my wiring or post my schematics? I didn't want to post a deluge of info unless that info would be useful.


Why is peak production highest in the 70's? Is that normal or is this a quirk for you due to the direction your panels face or something like that?

I have two Powerwall+ inverters so that's two 7.6 inverters. I don't

Looking at a previous email exchange with Tesla I found this "we installed 158 SR tiles at 72 watts a tile, 158 x 72 = 11,376. Divide 11,376 by 1000 and you get 11.376, which is the DC system size. The CEC rating factors in the inverters conversion efficiency which will not be 100%, hence why the AC rating is slightly lower than the DC rating." I was inquiring about why an email from my electric company said "Size: 10.0 kW AC-CEC" and that was Tesla's response. So I suppose this means that I should not expect to see more than 10.0 kW?

Or post photos of my wiring or post my schematics?

The raw DC Panel rating will always be higher than the AC output due to how the panels are oriented, inverter sizing and efficiency losses. If your PTO paperwork indicates that you have a 10.0 kW AC rating then that should indicate that your inverter(s) max out that number.

Posted your schematic wire drawing with all of the equipment that was installed should tell the true story.

 

[CrazyRabbit]

Your production might be limited by the powerwall charge rate…. How manny paw did you say you have?

 

[uscpsycho]

You are talking about two separate things.

1. What is the peak production I will see at any one time?

You will not see peak production of your DC system size at any one time, unless your system is ground mounted, pointed at the optimum angle, and on a specific time of day (or your system is ground mounted and tracks the sun). So, you will not see DC system size as your max peak production, nor should you care about that as production should be measured in weeks / months, not "peak inrush power at any specific time:"

2. Is it possible for my production to increase after pto on a tesla system?

Yes, since some systems with powerwall+ are put in a "self consumption only" mode, which means that the system curtains the solar production since pre PTO you can not back feed the grid. You may see increased production (daily production) after PTO, if your system is in this self consumption mode.

Note that for many of us prior to this, we were not able to (by policy anyway) turn our systems on AT ALL prior to permission to operate (PTO) as there was no "self consumption only" mode. It is entirely possible that you see increased DAILY production after PTO, but not increased PEAK production as a system size of X does not in any way, shape or form dictate what PEAK production is.


Here is just one (of a few) different threads here where people ask "I bought a system that was X size, I dont get X peak production, I was misled"

Solar Panels only generating about 60% [of peak production number]

I had 11.6 kW of solar panels and 3 Powerwalls installed about a month ago here in Miami, FL. It's summer so the days are pretty long, and even on the clearest day, I seem to only generate about 7.0 or 7.5 kW of power from the solar panels. Anyone else having this experience? I feel like I...

teslamotorsclub.com

I am inquiring about two separate things but you got the second question wrong.

The second question is not "Is it possible for my production to increase after pto on a tesla system?"

The second question is: Is it possible for my PEAK production to increase after pto on a tesla system?

So while I would like the first question to be answered, and I'd like to know, I think that question is harder to answer. But I don't think the second question is so hard to answer because it doesn't depend on any variables. Say my PW are at 50% and the climate is perfect for peak production. Will the peak production number be the same after PTO as it is today? We are not talking about sending power back to the grid here.

Your production might be limited by the powerwall charge rate…. How manny paw did you say you have?

I have three PW and two of them are PW+.

 

[jjrandorin]

I am inquiring about two separate things but you got the second question wrong.

The second question is not "Is it possible for my production to increase after pto on a tesla system?"

The second question is: Is it possible for my PEAK production to increase after pto on a tesla system?

So while I would like the first question to be answered, and I'd like to know, I think that question is harder to answer. But I don't think the second question is so hard to answer because it doesn't depend on any variables. Say my PW are at 50% and the climate is perfect for peak production. Will the peak production number be the same after PTO as it is today? We are not talking about sending power back to the grid here.



I have three PW and two of them are PW+.

PTO will have zero to do with your PEAK production (but peak (instantaneous) production is a very (very) poor metric to try to evaluate a PV system with).

 

[uscpsycho]

PTO will have zero to do with your PEAK production (but peak (instantaneous) production is a very (very) poor metric to try to evaluate a PV system with).

I am learning that peak production is not such an important variable. But before I knew this, when I complained to Tesla that my peak production was not as high as I expected, they told me that it was because I didn't have PTO and that after PTO my peak production would go up. As irrelevant as peak production might be in the big scheme of things, what they said is false. If I trusted them, I'd be expecting that peak number to go up after PTO and it would not.

As I've always understood it, nothing will change after PTO other than the fact that I will start to export my extra capacity to the grid. There is no other artificial cap. So theoretically, if I used so much power that my batteries never hit 100%, I would generate the same amount of solar power before and after PTO. The difference between before/after PTO is what happens when the batteries are at 100%. Correct?

 

[jjrandorin]

I am learning that peak production is not such an important variable. But before I knew this, when I complained to Tesla that my peak production was not as high as I expected, they told me that it was because I didn't have PTO and that after PTO my peak production would go up. As irrelevant as peak production might be in the big scheme of things, what they said is false. If I trusted them, I'd be expecting that peak number to go up after PTO and it would not.

As I've always understood it, nothing will change after PTO other than the fact that I will start to export my extra capacity to the grid. There is no other artificial cap. So theoretically, if I used so much power that my batteries never hit 100%, I would generate the same amount of solar power before and after PTO. The difference between before/after PTO is what happens when the batteries are at 100%. Correct?

As far as tesla and them telling you your peak production would go up, its very likely they made the mistake in assuming (which, "assume" I know) you were talking about "daily peak production" which its likely will go up, unless you are in fact consuming all solar you generate without your batteries getting to 100%.

I certainly wasnt there, so dont know, and I am not attemping to make an excuse for them, just to explain that in the vast majority of these cases, what people are asking about is "peak production" as in "My daily production is less than I expected", not "peak production" as in "my instantaneous production is not as high as I expected".

Its my belief they answered the question they are used to hearing, instead of the question you actually asked, or there was some other miscommunication between what you were asking and what information you received.

Peak instant production has nothing to do with PTO, but with inverter capacity, angle of the sun, etc, and peak instant production is never anything any PV installer every guarantees (even the ones with guarantees). The ones with guarantees guarantee yearly production.


Anyway, I doubt they intentionally tried to mislead you on "peak instant production".

As far as what I understand of your second statement, you are correct. As far as solar export, whether your production is curtailed at 100% or something less than that, and whether its "only on or off" or "scaled down as batteries get full" depends on the specific equipment and settings for curtailment of solar. Your solar is likely being curtained at something other than "batteries = 100 %", but in a general sense, what will change after PTO is you will be allowed to export solar, so your system will no longer be curtailed.

What your curtailment looks like now, we dont know. If you used enough power so that your batteries never got above 90%, I would feel better about saying "yes you are right", but there is some point between 90% and 100% where many newer systems start curtailing / cutting back solar PV if they can not export that power.

 

[nyprepper]

in my experience the Tesla support reps have terrible communication skills and are poor listeners. i would bet that the support rep was telling you "peak" output would improve after PTO because they were confusing the meaning of "peak" with the meaning of "total"

 

[charlesj]

... But before I knew this, when I complained to Tesla that my peak production was not as high as I expected, they told me that it was because I didn't have PTO and that after PTO my peak production would go up. As irrelevant as peak production might be in the big scheme of things, what they said is false. If I trusted them, I'd be expecting that peak number to go up after PTO and it would not.

...

Don't forget, while some people at Tesla are knowledgeable, you are not talking to engineers there who know all the ins and outs.

 

[uscpsycho]

As far as tesla and them telling you your peak production would go up, its very likely they made the mistake in assuming (which, "assume" I know) you were talking about "daily peak production" which its likely will go up, unless you are in fact consuming all solar you generate without your batteries getting to 100%.

I certainly wasnt there, so dont know, and I am not attemping to make an excuse for them, just to explain that in the vast majority of these cases, what people are asking about is "peak production" as in "My daily production is less than I expected", not "peak production" as in "my instantaneous production is not as high as I expected".

Its my belief they answered the question they are used to hearing, instead of the question you actually asked, or there was some other miscommunication between what you were asking and what information you received.

in my experience the Tesla support reps have terrible communication skills and are poor listeners. i would bet that the support rep was telling you "peak" output would improve after PTO because they were confusing the meaning of "peak" with the meaning of "total"

This is from an email last week. "Your solar system does not yet have permission to operate or be fully activated, the solar system will not produce the 11 KW until we receive permission to operate from the utility company."

According to that, they are throttling me and it has nothing to do with sending power back into the grid. They are saying no matter how much electricity I use, that I am artificially capped at some level of production below my max because my system is not "fully activated." And they are saying that this limitation is because I don't have permission from the utility company to produce 11 kW. Is this true or is this BS? (I'm DWP in Los Angeles for anyone wondering.)

Like I said above, my understanding was that the only limitation I have while in self-consumption mode is that I can't export electricity. I didn't think there was any limit to producing as much electricity as I can actually use.