Post Installation / Pre-PTO System Intentionally Limited?

[GateFather]

Just got off of a call with my project advisor and he said the system would be in "self-consumption" mode prior to PTO after installation, and output would be limited. I asked him whether this means limited in that it will not export to grid (known) or actually power limited. He said limited only in that it won't output to grid. Coincidentally, I just saw this post on Reddit of someone who just had their system installed and is in this "self-consumption" mode where their system seems to be vastly power limited. Is this really a thing? Why do they do it? Is it some kind of anti-consumerism where they don't want people to have lower/no energy bills AND no loan for however long it takes the utilities to give PTO? Or is there some technical limitation? If that is true, I wouldn't understand since even when PTO is granted and system is fully commissioned, it can be run in off-grid mode. How would that be different than self-consumption mode?

 

[jjrandorin]

Is this really a thing? Why do they do it?

Yes

Because you dont have permission to operate yet, they need to do it. In the past, we couldnt even turn the system on at all (if we chose to follow the instructions of the documents we signed during implementation), before we got final PTO from the utility.

 

[GregBallantyne]

In my case, there was no solar operation of any kind possible prior to PTO. The final connection was required for operation, and not made until after PTO followed by some inspections, then final connection, during meter swap. Grid operator does the meter swap. Had my config not been whole house backup, might have been different. With whole house backup, grid enters Gateway and Gateway powers load center. Meter pull is required as the disconnect for the final connection work.

 

[GateFather]

Yes

Because you dont have permission to operate yet, they need to do it. In the past, we couldnt even turn the system on at all (if we chose to follow the instructions of the documents we signed during implementation), before we got final PTO from the utility.

I get this if it was their policy. But why turn it on and limit it's power capabilities?

In my case, there was no solar operation of any kind possible prior to PTO. The final connection was required for operation, and not made until after PTO followed by some inspections, then final connection, during meter swap. Grid operator does the meter swap. Had my config not been whole house backup, might have been different. With whole house backup, grid enters Gateway and Gateway powers load center. Meter pull is required as the disconnect for the final connection work.

Interesting. My system will be whole-home backup as well, but my advisor told me I will be able to operate in self-consumption mode between install and PTO. It was not my normal project advisor whom I spoke with today, and this one seemed much less knowledgeable than my normal advisor. He was very wishy-washy with his answers including in regard to this.

 

[Vines]

I get this if it was their policy. But why turn it on and limit it's power capabilities?

Because you do not have permission to export power to the grid. Therefore you can only produce what you will use for loads or ESS charging.

 

[GateFather]

Because you do not have permission to export power to the grid. Therefore you can only produce what you will use for loads or ESS charging.

Oh right - so this means, for example, if I have 4 Powerwall 2s at 25% charged and 23.49kw DC / 20.9kw AC panel system, in ideal conditions, the panels should be able to generate up to their full potential, right? The Reddit poster has 2 PWs and their 6.48kw system in full sunlight is only generating 2.5kw with PWs at 83%.

 

[offandonagain]

With 4 Powerwalls you should be fine, as long as you can also discharge them to charge them up again the following day. Also, if you can charge your EVs during the day, that's a great way to use up excess solar that would have otherwise been curtailed. I don't think you'll be able to use Tesla's Charge on Solar before PTO, but you can approximate that with some manual work (by charging at the right time, setting a lower charge rate on the car, and using the Powerwalls as buffer when needed).

The Reddit post doesn't have enough details, but possibly has a bigger issue with production. Tesla does not limit generation other than the grid export limitation.

 

[GateFather]

With 4 Powerwalls you should be fine, as long as you can also discharge them to charge them up again the following day. Also, if you can charge your EVs during the day, that's a great way to use up excess solar that would have been otherwise been curtailed. I don't think you'll be able to use Tesla's Charge on Solar, but you can approximate with some manual work (by setting a lower charge rate on the car and using the Powerwalls as buffer when needed).

The Reddit post doesn't have enough details, but possibly has a larger production issue.

I plan to the house on PWs overnight during self-consumption time period which should leave a good runway for them to charge by solar during day. I have 2 Model Ys so charging the cars with excess solar that would be otherwise wasted during the day is a good idea. However, I think between the house and PWs, I will likely be able to make use of most of the solar during the day. I was just getting worried that for some reason the system would be curtailed unnecessarily based on the way my advisor didn't seem to know what he was talking about, and then the Reddit post.

 

[jjrandorin]

I was just getting worried that for some reason the system would be curtailed unnecessarily based on the way my advisor didn't seem to know what he was talking about, and then the Reddit post.

It WOULD be curtailed, if you couldnt use it all.

As it pertains to whatever else you might read about someone elses install, you have to look at that stuff (other peoples installs) as only generalities. These are home construction projects, and every one of them is different.

Even if you lived in a track home and someone else in your development with the same exact floorplan, roof etc was getting solar, it does not mean they have the same electrical loads as you so their install may be different.

So, in general terms, when a new PV install is done, if its grid tied at all (which is most of them but not all... and if a person is installing a non grid tied PV system they know it), we do not have a right to export anything at all to the utility until they give us the permission to do so (permission to operate).

As I said, in the past, there was no ability to operate in a non export mode for a grid tied PV system, that didnt involve the homeowner physically throwing the main breaker on their home and disconnecting themselves physically from the grid. Now, there is a non export mode that will curtail the PV if it would need to export some of the production, and you dont have PTO.

If you have the ability to generate loads (like charging an EV) then you can probably absorb the production by micro managing that. Not everyone has that luxury.

 

[jjrandorin]

if I have 4 Powerwall 2s at 25% charged and 23.49kw DC / 20.9kw AC panel system, in ideal conditions, the panels should be able to generate up to their full potential, right?

I missed this, but the answer to this is "maybe?" One of the most common confusion / complaints that people post when they join this subforum is something along the lines of:

=============================
"Hello everyone. I bought a (X)kW sized system (8 / 12/ 16 etc), but I never see "X" as power input in my Tesla app. What gives / Did I get ripped off / Is my system working properly?"
=============================

People buying a system the size of yours usually understand this, but just in case...... unless all of your panels are pointed directly at the sun in the perfect angle, plane, etc, it is likely your system may never generate peak power that is the same as the system size number.

 

[GateFather]

I missed this, but the answer to this is "maybe?" One of the most common confusion / complaints that people post when they join this subforum is something along the lines of:

=============================
"Hello everyone. I bought a (X)kW sized system (8 / 12/ 16 etc), but I never see "X" as power input in my Tesla app. What gives / Did I get ripped off / Is my system working properly?"
=============================

People buying a system the size of yours usually understand this, but just in case...... unless all of your panels are pointed directly at the sun in the perfect angle, plane, etc, it is likely your system may never generate peak power that is the same as the system size number.

Yeah definitely get this. Also why the panels are 23.49 but inverter is 20.9 because that 20.9 will cover likely 95% plus of production times over the course of the year, assuming there is maybe 5% during the peak of summer where maybe I get full production. Still unlikely in my case since 24 of my panels will fast northwest and 34 will face southeast.

 

[Vines]

Oh right - so this means, for example, if I have 4 Powerwall 2s at 25% charged and 23.49kw DC / 20.9kw AC panel system, in ideal conditions, the panels should be able to generate up to their full potential, right? The Reddit poster has 2 PWs and their 6.48kw system in full sunlight is only generating 2.5kw with PWs at 83%.

I suspect there is a smoothing algorithm that understands that there are likely 6 good production hours in a day, but if you have enough PV to fill the batteries in 2-3 hours, then there is no need to charge at full speed.

Imagine that the PW charged at max in the above example. All else being equal, the situation that would bring most customer complaints would be "My PV just stopped all afternoon! Come fix your broken $%!# If Tesla tells customers to expect that your system produces less than the maximum, then you can relax and go back to living your best life instead of worrying the system is broken.

 

[GateFather]

I suspect there is a smoothing algorithm that understands that there are likely 6 good production hours in a day, but if you have enough PV to fill the batteries in 2-3 hours, then there is no need to charge at full speed.

Imagine that the PW charged at max in the above example. All else being equal, the situation that would bring most customer complaints would be "My PV just stopped all afternoon! Come fix your broken $%!# If Tesla tells customers to expect that your system produces less than the maximum, then you can relax and go back to living your best life instead of worrying the system is broken.

Ah interesting. Good point. I’m thinking in my case the powerwalls will drain significantly overnight and their refilling plus home usage in summer will use a lot of the available solar generated power. That’s the hope at least!

 

[Rocket_man]

In my jurisdiction I had both a local city electrical inspection and the power company inspection. I attended the local inspection as did Tesla. The local inspector was not even an electrician and he looked at the install was 'impressed' and passed it. lol. But then the power company failed my install because I had the large '0' gauge wires from the gateway crossing over the '0' gauge wires from the feed to the panel. Tesla had to send a tech to the house to re-route the gateway line through a huge U-shaped conduit outside the main breaker box. Yes it is ugly. Then after this was okay'd by the power company they approved me to get the proper bi directional meter installed. Which I had to pay for. Only then could I get PTO. I forget how long this took. Months. But that whole time I was in self-consumption mode. The house ran off solar and PW, but once the PWs were full the panels would just drop their output to almost 0. Lots of issues with my install and PTO. Took over a year.

 

[GateFather]

In my jurisdiction I had both a local city electrical inspection and the power company inspection. I attended the local inspection as did Tesla. The local inspector was not even an electrician and he looked at the install was 'impressed' and passed it. lol. But then the power company failed my install because I had the large '0' gauge wires from the gateway crossing over the '0' gauge wires from the feed to the panel. Tesla had to send a tech to the house to re-route the gateway line through a huge U-shaped conduit outside the main breaker box. Yes it is ugly. Then after this was okay'd by the power company they approved me to get the proper bi directional meter installed. Which I had to pay for. Only then could I get PTO. I forget how long this took. Months. But that whole time I was in self-consumption mode. The house ran off solar and PW, but once the PWs were full the panels would just drop their output to almost 0. Lots of issues with my install and PTO. Took over a year.

When the powerwalls were full, and the panels would drop output to almost 0, was it less than the house was consuming? Meaning did they drop below the power needs of the home forcing grid usage or did they drop low because they could only supply to the demand?

 

[Rocket_man]

When the powerwalls were full, and the panels would drop output to almost 0, was it less than the house was consuming? Meaning did they drop below the power needs of the home forcing grid usage or did they drop low because they could only supply to the demand?

The panels were trying to balance their output with the house demand. It wasn't always exact, it may show 100 watts being exported for a short period. I'm not sure if that was real or just the limit of the gateway's ability to show what was really happening.