12.24kW, 2 PW Install in TX

[Flyer288]

Hi there

I had a 36 panel, 12.24kW solar and 2 Powerwalls installed recently. Still waiting for PTO (Centerpoint, expected Oct 16), but thought I'd share the install and ask a question about the panels. I'm west of Houston, TX.

• Ordered: July 23
• Installation: September 3, 4 and 7 (thunderstorms delayed the install)
• Inverter: SE11400H

Apart from the thunderstorms, the installation went well. The panels are spread across two roofs, with the Powerwalls in the garage. The crew were professional, neat and tidy. I have a couple of minor niggles about the conduit (between the roofs) and the alignment of a couple of panels looks off, but it's not something that most would notice (TMC forum members excepted )

The crew fitted soft start devices to the 3 A/C units. The lead was concerned about the load with only 2 Powerwalls, but if there was an outage, we would definitely turn 1 off and likely turn 1 more off.

The Powerwalls were charged to about 30%, but are now at 0%; I understand that won't harm them, but I'll be glad when they're back above that.

Layout:

Side of garage:

Main roof:

Garage:

Conduit detail (not quite level):

Powerwalls:

Now for the question; I noticed the panels seem to be marked. Didn't notice until after some heavy rain. Anything to worry about?

Overall, pretty pleased with how things have gone... so far.

 

[jjrandorin]

Welcome to TMC!. If it were me, I would definitely "test the system" at least long enough to get a full charge on the powerwalls. If there is sun for you tomorrow, I would power the system up, let the solar charge the batteries and open the main breaker so that you are not back feeding to the grid at all, and then run that way until the batteries get to 80-90%. You could then turn the system off, and your batteries wouldnt be sitting at zero.

I dont know about the smudges etc on the panels. If thats dirt or something, not that big a deal... if its footprints that dont come off, then ... I wouldnt like it on a new install but I dont know if it hurts anything.

 

[SoCal Dave]

I had some smudges and in a few days a layer of dust covered them. I wouldn't worry about it unless you think they have been physically damaged (doesn't look like it to me).

 

[bob_p]

You should have had 3 PowerWalls for a 12 KW system.

We have a 15.4 KW/4 PowerWall system in SW Houston - and even with 4 PowerWalls, we end up sending some excess power back to the grid during days with sun.

We are on a Free Nights plan (free electricity from 9PM to 9AM), so we aren't compensated for the excess energy we're sending back to the grid. Instead, we are using the solar panels and PowerWalls to eliminate as much of the grid power usage during the 9AM-9PM period. So far, we're using about 80% of our grid electricity during the Free Nights period - drastically reducing our energy bills...

Unfortunately your installer wall-mounted the PowerWalls, which will make adding a 3rd PowerWall more difficult, unless you can find additional wall space. For future expansion, it would have been better to floor mount the PowerWalls, since you could then have easily added an extra PowerWall in front of one of the existing PW.

Our 4 PowerWalls are floor mounted in two stacks in our garage.

 

[cridinger82]

unless your net metering rules suck in Houston. net metering is much more efficient especially in areas were they offer 1:1 retail rates. the efficiency drop by storing and then unloaded from batteries makes grid storage net metering the best next to just pulling from pv directly.


Main reason we only went with 2 power wall for our situation. they will sit in backup only mode for the most part.

 

[Flyer288]

Welcome to TMC!. If it were me, I would definitely "test the system" at least long enough to get a full charge on the powerwalls. If there is sun for you tomorrow, I would power the system up, let the solar charge the batteries and open the main breaker so that you are not back feeding to the grid at all, and then run that way until the batteries get to 80-90%. You could then turn the system off, and your batteries wouldnt be sitting at zero.

I dont know about the smudges etc on the panels. If thats dirt or something, not that big a deal... if its footprints that dont come off, then ... I wouldnt like it on a new install but I dont know if it hurts anything.

Thanks! Yes, my first post, learned a lot here already.

I'm reluctant to turn it on but certainly with looking into. Is there a step by step guide? Appreciate it's probably only a couple of steps, but wouldn't want to get it wrong.

Smudges, not sure what they are. Think a ladder will need to come out this weekend for a closer look.

 

[Flyer288]

I had some smudges and in a few days a layer of dust covered them. I wouldn't worry about it unless you think they have been physically damaged (doesn't look like it to me).

No, they don't look damaged. Thanks for the advice.

 

[jjrandorin]

Thanks! Yes, my first post, learned a lot here already.

I'm reluctant to turn it on but certainly with looking into. Is there a step by step guide? Appreciate it's probably only a couple of steps, but wouldn't want to get it wrong.

Smudges, not sure what they are. Think a ladder will need to come out this weekend for a closer look.

I am not looking at your specific system, but in general you normally:

1. Turn on the breakers for the inverters
2. Turn on the Inverters
3. Turn on the breakers for the powerwalls
4. Turn on the switches on the powerwalls

If it were my home, I turn on the breakers and inverters, wait 4-5 minutes to make sure they were up, then turn on the breakers and powerwalls, and then check to see if tesla app was showing production. If you know the powerwalls are at zero you likely can see them in your app.

I would put the powerwalls in backup only mode, to enable the solar to go directly to the batteries.

Once everything was producing, etc, I would keep an eye on it and shut it all down when the powerwalls hit 70-80 percent.

 

[Flyer288]

You should have had 3 PowerWalls for a 12 KW system.

We have a 15.4 KW/4 PowerWall system in SW Houston - and even with 4 PowerWalls, we end up sending some excess power back to the grid during days with sun.

We are on a Free Nights plan (free electricity from 9PM to 9AM), so we aren't compensated for the excess energy we're sending back to the grid. Instead, we are using the solar panels and PowerWalls to eliminate as much of the grid power usage during the 9AM-9PM period. So far, we're using about 80% of our grid electricity during the Free Nights period - drastically reducing our energy bills...

Unfortunately your installer wall-mounted the PowerWalls, which will make adding a 3rd PowerWall more difficult, unless you can find additional wall space. For future expansion, it would have been better to floor mount the PowerWalls, since you could then have easily added an extra PowerWall in front of one of the existing PW.

Our 4 PowerWalls are floor mounted in two stacks in our garage.

The original quote from Tesla was for 4, but I thought that was excessive. I'll be going with a Reliant Simple Solar Sell Back Plan, which I believe is net metering, as cridinger82 said, so unless I've misunderstood, we should be ok.

Agree about the mounting! The installer did ask where I wanted them, but at that time I didn't know (or had forgot) that they needed to be floor mounted if they were going to be stacked ... and he didn't inform me of that until after he had mounted them. Benefit of hindsight, they would be floor mounted to give me the option. As it is though, we do have enough wall space for one more, so that could be floor mounted for future expansion (but would mess with my sense of order).

 

[wjgjr]

I am not looking at your specific system, but in general you normally:

1. Turn on the breakers for the inverters
2. Turn on the Inverters
3. Turn on the breakers for the powerwalls
4. Turn on the switches on the powerwalls

If it were my home, I turn on the breakers and inverters, wait 4-5 minutes to make sure they were up, then turn on the breakers and powerwalls, and then check to see if tesla app was showing production. If you know the powerwalls are at zero you likely can see them in your app.

I would put the powerwalls in backup only mode, to enable the solar to go directly to the batteries.

Once everything was producing, etc, I would keep an eye on it and shut it all down when the powerwalls hit 70-80 percent.

To add to this - if you don't want to worry about any chance of sending power into the grid, I would add step "0", which is turn off the service disconnect. It will take longer to charge the PWs, but it should still happen soon enough - just only do this when you are generating enough solar to cover your home load and still charge.

Also, at least in our case (no idea if it is typical,) Tesla left our install with everything on - including all breakers - except the switch for the inverter. That meant their instruction to me was that when I got PTO, I would just need to flip one switch (or rotate it 90 degrees, in this case) to have everything running.

 

[Flyer288]

I am not looking at your specific system, but in general you normally:

1. Turn on the breakers for the inverters
2. Turn on the Inverters
3. Turn on the breakers for the powerwalls
4. Turn on the switches on the powerwalls

If it were my home, I turn on the breakers and inverters, wait 4-5 minutes to make sure they were up, then turn on the breakers and powerwalls, and then check to see if tesla app was showing production. If you know the powerwalls are at zero you likely can see them in your app.

I would put the powerwalls in backup only mode, to enable the solar to go directly to the batteries.

Once everything was producing, etc, I would keep an eye on it and shut it all down when the powerwalls hit 70-80 percent.

Great, thank you. The PWs are switched on already and in Backup-only mode. There isn't a new breaker for the inverter, so that would leave simply turning on the inverter.

 

[jjrandorin]

Great, thank you. The PWs are switched on already and in Backup-only mode. There isn't a new breaker for the inverter, so that would leave simply turning on the inverter.

You dont have a breaker anywhere labeled "PV" by the installer? Maybe its (the breaker) in your gateway if you have a gateway version 2?

 

[Flyer288]

To add to this - if you don't want to worry about any chance of sending power into the grid, I would add step "0", which is turn off the service disconnect. It will take longer to charge the PWs, but it should still happen soon enough - just only do this when you are generating enough solar to cover your home load and still charge.

Also, at least in our case (no idea if it is typical,) Tesla left our install with everything on - including all breakers - except the switch for the inverter. That meant their instruction to me was that when I got PTO, I would just need to flip one switch (or rotate it 90 degrees, in this case) to have everything running.

Got it, yes step 0 makes sense, thanks.

Yes, they left everything switched on, except the inverter. Just paranoid about sending anything to the grid!

 

[Flyer288]

You dont have a breaker anywhere labeled "PV" by the installer? Maybe its (the breaker) in your gateway if you have a gateway version 2?

No, they didn't add anything extra to the panel. But yes, I do have the Backup Gateway 2 and there is a breaker for the inverter, which is off. OK, understand now. Flip that breaker, turn on the inverter and we're good to go? (Bearing in mind step "0", as mentioned by wjgjr).

 

[wjgjr]

Got it, yes step 0 makes sense, thanks.

Yes, they left everything switched on, except the inverter. Just paranoid about sending anything to the grid!

For what it's worth, that was pretty much my daily routine before PTO - turn off grid in AM and then turn on inverter. In the PM turn off inverter, turn on grid. Since our system doesn't cover 100% of our usage for most of the year (particularly with the hot summer for us) it was only a couple times I could leave the system on over 24 hours.

As I suggest to everybody, it is worth reading the agreements you signed with your utility. In our case, I felt comfortable that I was not violating the agreement as long as I was always off grid when generating after inspection and before PTO. However, every utility has its own wording and its own level of interest in enforcing its agreements. And only you get to deal with any consequences.

 

[jjrandorin]

To add to this - if you don't want to worry about any chance of sending power into the grid, I would add step "0", which is turn off the service disconnect. It will take longer to charge the PWs, but it should still happen soon enough - just only do this when you are generating enough solar to cover your home load and still charge.

Also, at least in our case (no idea if it is typical,) Tesla left our install with everything on - including all breakers - except the switch for the inverter. That meant their instruction to me was that when I got PTO, I would just need to flip one switch (or rotate it 90 degrees, in this case) to have everything running.

Yeah I didnt type that (I had it typed actually and erased it) because I wasnt sure about telling someone to turn off their main breaker without knowing what their home electrical load was, etc at the time, and whether their PV would cover their home load.

People are absolutely allowed to Test their installs, so I figured that 5-10 minutes top of back feeding until the powerwalls kicked in would be ok, and with the powerwalls in backup only mode that + home load would be ok... but it still could backfeed into the grid for sure.

 

[jjrandorin]

No, they didn't add anything extra to the panel. But yes, I do have the Backup Gateway 2 and there is a breaker for the inverter, which is off. OK, understand now. Flip that breaker, turn on the inverter and we're good to go? (Bearing in mind step "0", as mentioned by wjgjr).

Yeah that should be good, bearing in mind step 0 if you want to ensure you dont send anything to the grid.

 

[charlesj]

T...

Also, at least in our case (no idea if it is typical,) Tesla left our install with everything on - including all breakers - ....

Perhaps this is why his battery discharged to 0 and the app may have been defaulted to self power?

 

[wjgjr]

Perhaps this is why his battery discharged to 0 and the app may have been defaulted to self power?

Given that I've found (since PTO) that my battery loses almost 2% of its capacity daily, I would think so as far as drain. And initially, I think it defaulted us to self-power because the solar wasn't available in the app until later in the install. Tesla told us they left everything on so the PWs could provide backup power if needed, but perhaps he didn't appreciate that it would take over a month in good times to get PTO (and more like 4 months for us.) Or maybe they figured we would turn on the system ourselves.


As an interesting note on testing, our agreements limit the on-grid testing to 2 hours. I don't think it says it has to be 2 continuous hours, however, so I suppose that could be used to cover any small energy export.

 

[bob_p]

unless your net metering rules suck in Houston. net metering is much more efficient especially in areas were they offer 1:1 retail rates. the efficiency drop by storing and then unloaded from batteries makes grid storage net metering the best next to just pulling from pv directly.


Main reason we only went with 2 power wall for our situation. they will sit in backup only mode for the most part.

Based on our actual data this year, 63% of our electricity is being generated from solar. With net metering, we'd pay for 37% of the electricity.

22% of our electricity has been during the daytime (9AM-9PM), when we pay for the electricity.

Since the rates for the net metering and Free Nights plans (in our area) are about the same (around 2X what we were paying under a fixed rate plan per KWh), we save significantly with Free Nights.

Experience by other solar customers could be different, which is why customers should use actual smart meter data to estimate the projected costs under the various electricity plans - since the assumptions used by the providers for projecting the cost of their plans are likely unrealistic and won't reflect actual usage.