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PTO Question

Yodeller

Member
Jan 1, 2016
30
6
Cupertino, CA
I had a 12.2kW system installed with 3 Powerwalls and I think my system was left working after the city inspection. I just received my final invoice and will be paying it today.

The thing is, even though the app says 3x batteries (with only 1 serial number listed), and my overnight power draw is constantly around ~0.8kW, I quickly drop from 100% at dusk to below 65% by dawn. Is that normal or something off with the math? I’m wondering if it’s only partially activated.

I asked a Telsa bot by text if I should leave my system on and he/she said if the system was left on by the installer, I should leave it on.

So to summarize my questions are:
1) is it normal to have just one serial number for the 3 batteries?
2) is it okay to leave the system running already with no PTO from PGE
3) is the system running but in some kind of disabled state given how quickly the battery percentage falls overnight? - almost 40% for a 3 PW system with only 0.8kW average discharge, without charging my car? Am I thinking about it wrong?

4)What’s the actual PTO sequence?
Does Tesla only request final payment after receiving receipt of PTO process underway with utility, should I take it as a sign of movement that they requested payment..?
I’m confused and not clear what to expect, even after asking.

Thanks
 

wjgjr

Active Member
May 11, 2020
1,157
887
Silver Spring, MD
To try and answer some of these questions

1) Not sure - as I look at the app I have, I'm not seeing serial numbers - I see an image that includes a PW with a "2x" on it, since I have 2. So I can't help with that - I may be missing where to look.
2) If you do not have PTO, most likely it is not supposed to be fully running - most likely some of the paperwork you signed with your utility and/or city covers this. I am surprised Tesla or the inspectors would leave it running.

However, one thing you might be able to do (and you can decide for yourself it this is something you want to do) is to run in an off-grid mode. That is, throw the service disconnect breaker so you are not connected to the grid and operate your system that way. That is what we ended up doing in the interim between inspection and PTO. Is it possible that is your current state? Are you drawing any grid power or operating solely on solar + PW?

3) Each PW officially has a 13.5 kWh usable capacity, though it has been found that it may in practice be a bit less than that. (For example, the app's range of 0%-100% actually represents 5%-100% of its true charge state. There are also standby losses in the PW that seem to range around 1% daily at a minimum - more if heating/cooling is needed, plus the round-trip losses when you are generating) You don't say how long overnight represents for you , but for 1 PW, the drop from 100% to 65% seems to represent maybe 4 kW used, or a touch more. This would equate to only 5 hours if it really is a constant 0.8 kW load.

The app should show you in the Energy Usage section how much power is going to/from the PW and will allow you to download your data. What is it showing for overnight home usage and powerwall draw? Also, each PW has an on/off switch. Are all switches on, and are the breakers in the on position?

4) It seems like Tesla's general policy is to require final payment after inspection and they state they will not apply for PTO until payment is received. I believe this was listed in our payment schedule and I think our final invoice also had a reminder about it. So I would not expect Tesla to proceed with PTO until they receive payment. However, if you have concerns about the PWs, it is fair to note that it is easier to get them to address issues before they have your money.
 

BrettS

Active Member
Mar 28, 2017
2,109
2,512
Orlando, FL
1) is it normal to have just one serial number for the 3 batteries?
Yes, totally normal. The serial number that shows up in the app is actually the gateway serial number and not one of the powerwall’s serial numbers. Each powerwall has a toggle switch on the side of it, you could double check to make sure that the switches on all three of your powerwalls are on, but I suspect that they are.

2) is it okay to leave the system running already with no PTO from PGE
Different utilities have different requirements, but it does seem unusual that the system would be on before PTO. If the installer left it on then they should know what they are doing.

3) is the system running but in some kind of disabled state given how quickly the battery percentage falls overnight? - almost 40% for a 3 PW system with only 0.8kW average discharge, without charging my car? Am I thinking about it wrong?

The system should be either on or of. There isn’t really a ‘sort of on’ option.

Exactly how long is ‘overnight’? If you’re running in self powered mode or off grid then the powerwalls will be supporting your house from sundown to sunup, so in addition to overnight they will be powering you through the evening too. I suspect that you’re averaging more than .8kW during the evening when everyone is still awake, but even so, say 7pm to 8am is 13 hours. .8kW over 13 hours would be 10.4kWh. Assuming that you can get the full 13.5kWh from each powerwall that would be a total of 40.5kWh from three. If you had the full 40.5kWh and used 10.4kWh that would bring you down from 100% to about 74%.

However, as mentioned before, you really don’t get a full 13.5kWh from each powerwall, and as I said above, I suspect that you may be using more than .8kW over some of that time, so taking both of those factors into account I don’t think that winding up at 65% in the morning is unreasonable.
 
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jboy210

Supporting Member
Dec 2, 2016
4,917
3,010
Northern California
I had a 12.2kW system installed with 3 Powerwalls and I think my system was left working after the city inspection. I just received my final invoice and will be paying it today.

The thing is, even though the app says 3x batteries (with only 1 serial number listed), and my overnight power draw is constantly around ~0.8kW, I quickly drop from 100% at dusk to below 65% by dawn. Is that normal or something off with the math? I’m wondering if it’s only partially activated.

I asked a Telsa bot by text if I should leave my system on and he/she said if the system was left on by the installer, I should leave it on.

So to summarize my questions are:
1) is it normal to have just one serial number for the 3 batteries?
2) is it okay to leave the system running already with no PTO from PGE
3) is the system running but in some kind of disabled state given how quickly the battery percentage falls overnight? - almost 40% for a 3 PW system with only 0.8kW average discharge, without charging my car? Am I thinking about it wrong?

4)What’s the actual PTO sequence?
Does Tesla only request final payment after receiving receipt of PTO process underway with utility, should I take it as a sign of movement that they requested payment..?
I’m confused and not clear what to expect, even after asking.

Thanks

How did you measure the 0.8Kw draw? You might check the "Energy Use" graph.

If you have A/C and it ran that could easily pull 4-5 kW. Similar to running a dryer or electric oven or range. Pool pumps use 2-3 kw. Even a hairdryer or waffle iron can draw around 1.5 kW It is pretty shocking to see how these everyday features of our home use so much power.

Another thing is to see if the PW are on and have a green light bar glowing. Also, check the generation panel breakers for the Powerwalls and make sure they are on.
 
Last edited:

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,097
8,964
Riverside Co. CA
I find it strange that tesla would leave a "solar + powerwall" system on, but not strange that they would leave a "powerwall added to existing, permitted, previously interconnected system" on.

If you are adding powerwalls to your existing solar, you already have an interconnect agreement for solar, and having battery storage actually reduces how much you are exporting. Once you pass the city / local inspection for "fit for use" the rest is just paperwork changing your existing interconnect agreement.

That only applies to powerwalls added to existing solar that was previously interconnected though. If you installed both solar and powerwalls at same time, then you dont have an existing interconnect agreement, and shouldnt be backfeeding anything to the grid until you get PTO, except for "tests" to ensure the system is working.
 

MJ_CA_2019

Member
Aug 19, 2020
105
26
Central CA
I find it strange that tesla would leave a "solar + powerwall" system on, but not strange that they would leave a "powerwall added to existing, permitted, previously interconnected system" on.

If you are adding powerwalls to your existing solar, you already have an interconnect agreement for solar, and having battery storage actually reduces how much you are exporting. Once you pass the city / local inspection for "fit for use" the rest is just paperwork changing your existing interconnect agreement.

That only applies to powerwalls added to existing solar that was previously interconnected though. If you installed both solar and powerwalls at same time, then you dont have an existing interconnect agreement, and shouldnt be backfeeding anything to the grid until you get PTO, except for "tests" to ensure the system is working.

This was my experience as well. I had the intention of doing solar and powerwall all along but my projects ended up getting split into two.
When the solar was installed everything was shut off until receiving PTO from the utility. When the powerwalls were installed and signed off by the city later, they were left on even though the utility interconnection agreement hadn't been fully amended / PTO for the batteries themselves hadn't been received. Because the powerwall doesn't export to the grid itself the utility would have to do some analytics on my power usage to see that my batteries were enabled. Not worth their time when they had already inspected and approved the system which can backfeed the grid in the solar project.
 

jboy210

Supporting Member
Dec 2, 2016
4,917
3,010
Northern California
I find it strange that tesla would leave a "solar + powerwall" system on, but not strange that they would leave a "powerwall added to existing, permitted, previously interconnected system" on.

If you are adding powerwalls to your existing solar, you already have an interconnect agreement for solar, and having battery storage actually reduces how much you are exporting. Once you pass the city / local inspection for "fit for use" the rest is just paperwork changing your existing interconnect agreement.

That only applies to powerwalls added to existing solar that was previously interconnected though. If you installed both solar and powerwalls at same time, then you dont have an existing interconnect agreement, and shouldnt be backfeeding anything to the grid until you get PTO, except for "tests" to ensure the system is working.

They left my solarRoof + PWs on and pushing back to the grid. The last part of the install was the commissioning and checking cables. And as soon as that was done they packed up and left.

After seeing the push back to the grid I called the lead on our install and he said "Opps, If your meter is reading negative (which it was) you should shut that down".
 
Last edited:

getakey

Active Member
Jan 28, 2020
1,112
358
95762
I had solar installed first and PWs a year and a half later. In both cases, system was running before I got PTO. For the initial solar, I got the PTO about 2 weeks after install. For the PWs, it took 2 months to get PTO, but system was running the whole time
 

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