Are loads on main panel still powered by solar?

[hobapolis]

Hello!

I'm getting some mixed answers on this from Tesla support though I thought I'd pose the question here:

I have 2 Powerwalls and a 12.24 kW system; plenty for my home in Arizona. A few months after the PV installation was done, we had a pool installed. The pool people put the power for the equipment on the "main" breaker box outside my home (compared to the sub panel in my garage that backs up everything with the powerwalls). My question is this:

During the day, is my pool equiptment powered by solar or by the grid? Tesla said it was powered by the grid since it wasn't on the same breaker box as all the backed up loads. This is a relatively important detail as we'd like to get a heat pump installed but we'd rethink it if the panels aren't powering it during the day.

 

[hobapolis]

Thats because your loads in your main panel are not visible to the tesla app, as you already found out. Not visible in the tesla app = not visible to PV / Powerwalls, nor will that power be counted in anything telsa is monitoring.

This part is crazy to me. I would think the PV would power whatever was in either load...backed up by the PW or not. I guess I don't mind eating the costs of whatever is on the main panel at night but the idea that that so much of my solar is going to waste will drive me nuts.

I only get $0.028/kWh i send back to the grid so i'd much rather put that power to use in my home than sell it back so cheaply.

 

[jjrandorin]

This part is crazy to me. I would think the PV would power whatever was in either load...backed up by the PW or not. I guess I don't mind eating the costs of whatever is on the main panel at night but the idea that that so much of my solar is going to waste will drive me nuts.

I only get $0.028/kWh i send back to the grid so i'd much rather put that power to use in my home than sell it back so cheaply.

Are you absolutely positive that bottom statement is true? Many people seem to get confused on what their net metering compensation is. In most cases, you get credit for what you put in at the rate you would have consumed at that time at (new CA NEM 3 not withstanding).

The low number of credit you are talking about normally occurs during the TRUE UP period, not on a monthly basis.

TL ; DR, that number is normally the amount they pay you at the end of the year for excess electricity, not what you get credited for while you generate it.

 

[hobapolis]

Are you absolutely positive that bottom statement is true?

Pretty sure:

>The Electric Vehicle (EV) Export Price Plan has no monthly demand charge. You pay only for the energy from the grid you use, and any excess energy you generate is credited at a fixed rate – 2.81 cents per kWh – and subtracted from your bill.

From: Electric Vehicle Export Price Plan for solar customers

 

[Vines]

I think all PW installs have a CT on the main panel. This is how they show you the current grid load. I think they need to compare what's on the grid side vs the backup side.

But I am not one hundred percent certain where this CT is placed. On my system I only have one load, my car charger, on the Main Panel. When my car chargers I can see that load in the grid and home graphs. And if the grid is down, the charger will not be supplied by power from solar or the PWs.

On this image the energy used on the far left (at midnight) is my car charging.

View attachment 756941

The CT which measure home load are by default placed inside the Tesla Gateway, and only capture the backed up loads unless additional CT's are installed.

Those additional CT's can be a single set around the main feeds, or electronically aggregated multiple sets which are around individual breakers or the 2x200A main breakers of a 400A service panel.

As for the OP, I would call up Tesla and explain to them that your home consumption is not being captured by the app. They might come add or move some CT's around, or they might tell you that you added loads after they installed the system so you are SOL.

 

[hobapolis]

or they might tell you that you added loads after they installed the system so you are SOL.

Kind of feel like this could be where this is going....unless i buy a 3rd powerwall and move everything to the sub panel.

@Vines i'm just kind of shocked that this wasn't better explained to me when i was buying everything. If they would have told me that things NOT on the backup sub panel ALSO would NOT be powered by PV i would have thought about everything WAY differently. Maddening.

 

[aesculus]

The CT which measure home load are by default placed inside the Tesla Gateway, and only capture the backed up loads unless additional CT's are installed.

Those additional CT's can be a single set around the main feeds, or electronically aggregated multiple sets which are around individual breakers or the 2x200A main breakers of a 400A service panel.

As for the OP, I would call up Tesla and explain to them that your home consumption is not being captured by the app. They might come add or move some CT's around, or they might tell you that you added loads after they installed the system so you are SOL.

Now I am going to have to open up my main panel and see how it is measured. I only have 1 breaker in there and IIRC the leads from the meter are not really accessible and were too wide for any type of CT, but I didn't look here during the install.

 

[BGbreeder]

Just to be clear; the Tesla app (and gateway) may not be measuring those loads, but when the gateway sends power to the grid, that solar power is available to your other loads. Power exported from the gateway is thus available to those loads behind the meter. The flip side is that those loads can and will draw from the grid with no offset from your powerwalls, since the gateway doesn't have a way to measure that the load exists. I.e. excess solar feeds through to power those loads when excess solar is available, but Powerwalls are never going to actively power those main panel loads.

TL;DR: as others have written, you will need a set of CTs on the power in/out of the main panel for your gateway to be able to offset the main panel demand with Powerwalls.

All the best,

BG

 

[Big Earl]

Just to be clear; the Tesla app (and gateway) may not be measuring those loads, but when the gateway sends power to the grid, that solar power is available to your other loads. Power exported from the gateway is thus available to those loads behind the meter. The flip side is that those loads can and will draw from the grid with no offset from your powerwalls, since the gateway doesn't have a way to measure that the load exists. I.e. excess solar feeds through to power those loads when excess solar is available, but Powerwalls are never going to actively power those main panel loads.

TL;DR: as others have written, you will need a set of CTs on the power in/out of the main panel for your gateway to be able to offset the main panel demand with Powerwalls.

All the best,

BG

With that in mind, the best time for OP to run his pool equipment is during the day when solar is producing.

 

[aesculus]

Now I am going to have to open up my main panel and see how it is measured. I only have 1 breaker in there and IIRC the leads from the meter are not really accessible and were too wide for any type of CT, but I didn't look here during the install.

OK. I opened my panels and this is what I discovered in terms of CT placements:

• In the GW panel I have a set of CT's that is going to the backup load panel. So essentially all of loads minus the car charger
• In the main panel I have two breakers. One for the charger and one for the backup panel. The car charger has a set of CTs on it
• My backup panel is basically a load center for a bunch of other panels scattered around my property. One of those panels is a separate building with almost no load (some occasional lighting). That building has a solar roof installed after the PWs were installed and a set of CTs were added on that breaker which are aggregated with the next panels CT's.
• Solar and PW panel. This panel has breakers for the PWs and two additional solar systems and those are measured with an additional set of CT's

So all in all I have 4 sets of external CTs: car charger, backup loads, solar roof, other solar.

 

[aesculus]

I.e. excess solar feeds through to power those loads when excess solar is available, but Powerwalls are never going to actively power those main panel loads.

TL;DR: as others have written, you will need a set of CTs on the power in/out of the main panel for your gateway to be able to offset the main panel demand with Powerwalls.

I guess I need to do a mini experiment here. I need to charge my car for a few minutes during peak and see if the PWs supply that power. Stand by.

 

[jjrandorin]

I guess I need to do a mini experiment here. I need to charge my car for a few minutes during peak and see if the PWs supply that power. Stand by.

They do for me (powerwalls provide power to my Tesla wall connector, that is in the main panel, not the backup loads panel. If I click "start charging" my home load will spike up to exactly what my car charger is requesting, and the energy will come from some combination of Solar (first), Powerwalls (second) Grid (third) because I am in self powered mode and thats how power is allocated.

In My case, my backup loads panel is inside my garage on the same wall and basically same space as my main panel, except my main panel is outside the garage on an exterior wall, and the backup loads panel is inside the garage about 4 feet from that location. Since all my equipment is so close (all on same wall, either inside the garage or outside on the side of the house), it likely made this very easy for them to do for me.

Of course, I believe this is a case by case thing, completely depending on ones own physical setup, CTs etc, so thats why I said "It depends" in the first response.

 

[hobapolis]

I opened my panels and this is what I discovered in terms of CT placements:

How hard is it to identify CT placement?

 

[Vines]

How hard is it to identify CT placement?

CT placement is pretty obvious. Each CT looks like a small plastic donut wrapped around the wire. It will have smaller wires attached to the CT itself, which may either plug into the Gateway or into a Neurio remote meter

If you are comfortable removing the dead fronts, take a picture of the inside of each panel, the CT should be obvious.

 

[hobapolis]

If you are comfortable removing the dead fronts

There's a first time for everything right?

 

[miimura]

How hard is it to identify CT placement?

Easy.

Gateway 1, Original Grid CT Placement, Neurio CT Connection point circled (not my photo or system)

Gateway 1, Grid CT relocated to main panel, solar CTs at bottom (my system)

Main Panel, Grid CT relocated to conductors between main breaker and main panel bus.

 

[Vines]

There's a first time for everything right?

It is unlikely to have anything dangerous, as long as you are careful. Just don't let the deadfront fall into the panel itself. Control it and make sure if it falls, it falls outside not inside the panel.

However, I have seen some crazy stuff behind the deadfront. One time I saw a "line side tap" made by driving a sheetrock screw into the main L2 conductor. Then they wrapped a #12 wire around that screw, and taped the whole thing off with electrical tape.

If a dead font had hit that screw head plus any grounded object it would not have been pretty.

 

[hobapolis]

Here's my main panel:

 

[Vines]

Here's my main panel:

View attachment 757159

If that is a SC3042M200PS then it could have had a 200A 4 pole branch circuit breaker landed on the bus and all loads relocated and backed up (if desired) instead of the 125A conenction.

If it is the panel I suspect, the installer should have installed CT meters in the line side compartment above the main breaker and under that shield. This way, all your home loads would be captured.

 

[hobapolis]

If that is a SC3042M200PS then it could have had a 200A 4 pole branch circuit breaker landed on the bus and all loads relocated and backed up (if desired) instead of the 125A conenction.

If it is the panel I suspect, the installer should have installed CT meters in the line side compartment above the main breaker and under that shield. This way, all your home loads would be captured.

Doesn't sound like there's a safe way to determine that.. i'm not really comfortable unscrewing any shielding i don't think.

 

[Vines]

Doesn't sound like there's a safe way to determine that.. i'm not really comfortable unscrewing any shielding i don't think.

I already know what you would see so there is no need.
Just confirm this panel is the model number I called out. It is found at the top left of the large sticker on the inside of the door.

Regardless, there are no CT under there currently, if there were you would see the small wires going to it from a Neurio meter.