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Recommendation to add EV charger to PV+ESS "whole home" backup

holeydonut

Supporting Member
Jun 27, 2020
1,228
726
East Bay NorCal
I guess I may be one of the few homeowners on this forum that don't actually own an EV. But I went for PV+ESS first due to the urgency (at the time) around the federal investment tax credit.

Now I'm looking forward to trying to get a EV, and more importantly an EV charger in my home. I'm kind of confused where this EV charger would be wired. My debacle PV+ESS project morphed from a partial home backup to a whole home backup.

I have a 200 A service coming into my main panel, and this feeds the Tesla Energy Gateway 2 (TEG2). The optional internal panelboard is used as a generation panel (3 Powerwalls) and is connected the backup side of the TEG2. The other backup lugs are connected to a 200 A sub-panel that ultimately feed and backup all of my home loads.


So for options:

1) The EV charger could be fed from the 200 A sub-panel that serves the rest of my home. But if there is a power outage at night, the EV could take all my battery power and leave my home with nothing. Unless, somehow the EV chargers can be intelligently load-shed or triggered to turn off in the event of a grid power outage. I guess this approach would be cool if ever they allow V2Grid (or V2Home)

2) The EV charger could go on a new non-backup sub panel that feeds off of the left side of the Gateway 2. But I don't know if the TEG2 still has room to access the non-backup lugs when the optional internal panelboard is in place. If I were able to do this approach, would I need to get an authorized Power Ranger back to my house to add CTs and configure the TEG2? Or is the TEG2 already smart enough to sense loads on the non-backup side without adding CTs or doing any admin/setup?

3) The EV charger could be put directly into the 200 A main panel. If allowed, I guess I'd definitely need to get a Power Ranger out here to add the CTs so the PV energy could find its way to the EV charger.


This all made perfect sense to me back when I was doing a partial home backup since there was a sub-panel all raring to go for non-backup loads like an EV charger. I didn't really think about how to add an EV charger to a "whole home" backup until now.
 

Ampster

Active Member
Oct 5, 2012
1,746
466
Sonoma, California
I have a hybrid inverter with 28kWh in LFP batteries and I will give you my charging philosophy of charging my two Teslas. I have two charging receptacles a 50 Amp one connected to my main service panel and a 30 Amp one connected to the load panel which is powered by the hybrid inverter. This panel is often called critical, essential or protected loads panel. Almost all of the time I use the EVSE connected to my main panel. I can reduce the charge rate and do that to just use the available solar energy. That is usually done if i am trying to manage my balance as I near my True Up. The only time I would use the smaller receptacle would be during a power outage and I would probably only do it from solar once my house batteries were charged.
My philosophy is based on the fact that I do not want to cycle my house bank more than necessary. I also have enough Superchargers near me that do not seem to be affected by the same power outages that affect my home. It all depends on where you are standing.
A comment on your option 3), the PV generation will find its way to your main panel and to the grid regardless of whether you have a power ranger.
 

gpez

Member
Apr 25, 2019
651
529
USA
@holeydonut also take care not to exceed your PW's capacity to provide power (3x Powerwalls = 15kW sustained) as you look to add a large load to your panels.

Tesla's new wall chargers can be configured to communicate with the Powerwall to prevent this issue: Tesla Powerwall update makes it smarter during a power outage - Roadshow (cnet.com)

Personally I have my EV charger on the non-backed up loads and similar to @Ampster I can use a lower amp charger if the power is out and manage it manually. But I don't have a Tesla (yet?) :)
 

holeydonut

Supporting Member
Jun 27, 2020
1,228
726
East Bay NorCal
Thanks gpez! Looks like Tesla solved the dilemma with the smart-communication between Gateway and the Tesla Charger. I guess this means I can put the Tesla Charger on the home/backup loads panel since the software will intelligently "shed" that load in the event of a grid failure.

I guess I just need to find an authorized Tesla Charger electrician. I just hope there isn't special configuration/modification on the Powerwall or Gateway software that requires a Power Ranger.
 

miimura

Well-Known Member
Aug 21, 2013
6,155
5,748
Los Altos, CA
Thanks gpez! Looks like Tesla solved the dilemma with the smart-communication between Gateway and the Tesla Charger. I guess this means I can put the Tesla Charger on the home/backup loads panel since the software will intelligently "shed" that load in the event of a grid failure.

I guess I just need to find an authorized Tesla Charger electrician. I just hope there isn't special configuration/modification on the Powerwall or Gateway software that requires a Power Ranger.
It's not actually that direct. The Powerwall and the car are both talking to the cloud and if they're on the same account they can coordinate. It would actually be better if the networked Gen3 Wall Connector was in the loop. That would allow things like controlling a car that belongs to someone else or using a Tesla to J1772 adapter to charge a different brand car. There is still lots of room to improve these features. Even things like charging only with Surplus Solar should be easy for Tesla to implement, but it's not there yet.
 
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gpez

Member
Apr 25, 2019
651
529
USA
It's not actually that direct. The Powerwall and the car are both talking to the cloud and if they're on the same account they can coordinate. It would actually be better if the networked Gen3 Wall Connector was in the loop. That would allow things like controlling a car that belongs to someone else or using a Tesla to J1772 adapter to charge a different brand car. There is still lots of room to improve these features. Even things like charging only with Surplus Solar should be easy for Tesla to implement, but it's not there yet.

It's not supported directly by Tesla but if you're a bit tech savvy you can look at TWCManager. It only supports TWCv2 but does all of this stuff and with a bit of scripting magic you can directly integrate it with the Powerwall local API.
 

holeydonut

Supporting Member
Jun 27, 2020
1,228
726
East Bay NorCal
Hmmm I guess the software behind this smart load shedding is still in the works.

It'll still be good to know if the non-backup lugs are available if the internal panelboard is installed... and whether the Gateway is already smart enough to balance load from PV sources to that circuit when the utility is operating. Does anyone on the Energy Forum have a TEG2 with the optional internal panelboard but their EV being charged on the non-backup side?
 

Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
The non backup lugs are still available when the internal panelboard is connected. You could run them to a small 60A disconnect and then to a HPWC if you choose.

We typically put any other chargers *except Tesla off the backup system, unless the customer requests otherwise. Granted there is some functionality deficiency, the basics are there: the PW batteries will not deplete charging the car during a blackout unless the customer wants that.

Hopefully in the future the Gen. 3 chargers network ability will be more completely working in with the Powerwall ecosystem.
 

CrazyRabbit

Member
Apr 21, 2020
379
115
Fort Worth TX
add the charger to your main panel, add a 30 or 50 amp plug in your garage so you could charge in a blackout if needed. this will also allow you to use excess solar in a blackout, if your home to charge that is...
 

Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
add the charger to your main panel, add a 30 or 50 amp plug in your garage so you could charge in a blackout if needed. this will also allow you to use excess solar in a blackout, if your home to charge that is...

He has a 200A breaker in there and a 225A bus, Per the 2017 NEC 705.12.B.2.3.c only a 25A breaker would be allowed, and this is a valid option if 25A is a fast enough charge.

Practically, using a 60A branch circuit in the MSP, and setting a export limit in the GW2 of 60A along with the required CT and labeling could be set and this would also be a safe installation and 2020 NEC compliant.
 

holeydonut

Supporting Member
Jun 27, 2020
1,228
726
East Bay NorCal
The non backup lugs are still available when the internal panelboard is connected. You could run them to a small 60A disconnect and then to a HPWC if you choose.

We typically put any other chargers *except Tesla off the backup system, unless the customer requests otherwise. Granted there is some functionality deficiency, the basics are there: the PW batteries will not deplete charging the car during a blackout unless the customer wants that.

Hopefully in the future the Gen. 3 chargers network ability will be more completely working in with the Powerwall ecosystem.


Lol I guess all of my threads point back to @Vines. I may not be understanding your reply correctly though... let me try to reiterate what I think you're saying ...

So if I get a Tesla charger, I can include the charger on the backup loads panel since the Tesla charger is smart enough to not deplete the PW's during a blackout. But if I really wanted to charge an EV during a blackout I can override the settings and charge with solar or ESS.

But if I get a non-Tesla charger, I can add it to the non-backup side since the non-backup lugs are still available. This means during a blackout, definitely no energy is making it to the non-Tesla charger. But when the grid is operational, the TEG2 already has internal CTs to help me balance load to the non-backup side. This means some solar or ESS energy could actually make it to the non-Tesla charger when the grid is up.
 
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holeydonut

Supporting Member
Jun 27, 2020
1,228
726
East Bay NorCal
He has a 200A breaker in there and a 225A bus, Per the 2017 NEC 705.12.B.2.3.c only a 25A breaker would be allowed, and this is a valid option if 25A is a fast enough charge.

Practically, using a 60A branch circuit in the MSP, and setting a export limit in the GW2 of 60A along with the required CT and labeling could be set and this would also be a safe installation and 2020 NEC compliant.


Yeah one of the reasons the PG&E T-Man crapped all over my install the first time was my new main service panel wasn't "safe." Sunrun's draw-up had two 125 A breakers going into a new "solar ready" main panel with a 225 A busbar. One end of the busbar had a 125 A going to the non-backup loads. The other end of the busbar had a 125 A going to the TEG2 for home loads/generation/ESS. Among a bunch of other perceived violations, the T-man added the two 125 A's up, and said I was exceeding the 200 A service and 225 A busbar.

The irony in this is that the opposite occurred when I got a PG&E Planner on the phone to right the ship. The planner looked at my old/existing panel and saw I had a 90 A and a 70 A breaker on the same busbar. And, he said only one breaker mattered in this configuration. So he concluded that I "must have 100 A" service since it's incorrect to add the two together.

So which is it PG&E? Add them together? Or you take the greater of the 2?
 
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Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
Lol I guess all of my threads point back to @Vines I may not be understanding your reply correctly though... let me try to reiterate what I think you're saying ...

So if I get a Tesla charger, I can include the charger on the backup loads panel since the Tesla charger is smart enough to not deplete the PW's during a blackout. But if I really wanted to charge an EV during a blackout I can override the settings and charge with solar or ESS.

But if I get a non-Tesla charger, I can add it to the non-backup side since the non-backup lugs are still available. This means during a blackout, definitely no energy is making it to the non-Tesla charger. But when the grid is operational, the TEG2 already has internal CTs to help me balance load to the non-backup side. This means so solar or ESS energy could actually make it to the non-Tesla charger when the grid is up.

You totally 100% got it correctly. The internal 100A lugs of the non backup side are metered, but have no other overcurrent protection. Any device you attach here needs a breaker disconnect such as the QO200TR.
Its actually the car that controls it. The Model 3 can be set to not charge when Powerwalls are in backup mode, though I haven't confirmed they fixed this on the S and X cars. It was labeled as coming soon around January.
 

Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
Yeah one of the reasons the PG&E T-Man crapped all over my install the first time was my new main service panel wasn't "safe." Sunrun's draw-up had two 125 A breakers going into a new "solar ready" main panel with a 225 A busbar. One end of the busbar had a 125 A going to the non-backup loads. The other end of the busbar had a 125 A going to the TEG2 for home loads/generation/ESS. Among a bunch of other perceived violations, the T-man added the two 125 A's up, and said I was exceeding the 200 A service and 225 A busbar.

The irony in this is that the opposite occurred when I got a PG&E Planner on the phone to right the ship. The planner looked at my old/existing panel and saw I had a 90 A and a 70 A breaker on the same busbar. And, he said only one breaker mattered in this configuration. So he concluded that I "must have 100 A" service since it's incorrect to add the two together.

So which is it PG&E? Add them together? Or you take the greater of the 2?

Both interpretations are wrong lol. Service size is determined by the size of the wires, and the main breaker. In a no main breaker (MLO panel) situation where both the 90 and the 70A are on the line side, it is supposed to be load calculations for the structure, and the physical limitations of the panel that ensure safety.

In reality its often the wild west. I remember seeing a picture where someone had a drywall screw into the main conductors as a "Line side Tap" then wrapped the smaller wire around it, and taped up the whole thing.
 

Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
Tesla definitely recommends putting the Tesla chargers on the backup circuit. I assume this is because V2G doesn't work otherwise, and gives customers full flexibility.

Before this functionality, we tended to put Tesla chargers off the backup system but now we try to get them on the backup side.
 

holeydonut

Supporting Member
Jun 27, 2020
1,228
726
East Bay NorCal
Both interpretations are wrong lol. Service size is determined by the size of the wires, and the main breaker. In a no main breaker (MLO panel) situation where both the 90 and the 70A are on the line side, it is supposed to be load calculations for the structure, and the physical limitations of the panel that ensure safety.

In reality its often the wild west. I remember seeing a picture where someone had a drywall screw into the main conductors as a "Line side Tap" then wrapped the smaller wire around it, and taped up the whole thing.


Haha the dream is to be the architect of your own new construction...

BTW, is there a reason why people buy a Tesla but then do not get a Tesla charger? Like I noticed some of my neighbors have a Tesla but they didn't have a Tesla charger because their electrician said the non-Tesla ones were better and installed whatever made sense at the time

And I have not seen seen someone with a non-Tesla get a Tesla charger (The Volt / Volvo XC90 T9 hybrid / Aviator Hybrid owners didn't consider putting a Tesla charger in their house). Aside from the load-shedding during a blackout feature, are they otherwise all the same?
 

Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
In my opinion they are not the same, its about power, cost, and longevity.

I personally prefer the Gen 2 HPWC, which maxes out any Tesla, except an older S with dual chargers, at 48A on a 60A breaker. 48A is good for about 38 mph in model 3 and is plenty. There are currently some issues with the Gen 3 units, though they might be getting resolved, I haven't really checked lately. We also have 2 Juicebox 40A units at work which seem to work fine after a few years. I expect to replace my primary wall charger every 3-5 years.

Most other brand chargers have a 40A or 50A max breaker for a 32 or 40A continuous charge. Some other charger brands are also networked, and have some app functionality. Other brands use the J1772 non locking plug standard

The Tesla ones have a special locking connector that you really want if you have a Tesla imo. The Tesla cars come with the J1772 adaptor, but its clunky as a primary solution and you lose the push button on the charger handle to open the charge port on the car.

I am not sure how many other BEV can even take advantage of 48A worth, so dont care to use a larger charger. Many have such small batteries that might exceed the C rating on the charge side. Only the Taycan can take more than 40A I think. I just looked up the Bolt and I-Pace and neither can take more than 32A.
 

jboy210

Supporting Member
Dec 2, 2016
4,910
3,007
Northern California
Tesla definitely recommends putting the Tesla chargers on the backup circuit. I assume this is because V2G doesn't work otherwise, and gives customers full flexibility.

Before this functionality, we tended to put Tesla chargers off the backup system but now we try to get them on the backup side.

Tesla has V2G?
 

Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
Tesla has V2G?

Not currently, but it is clear this is a possibility in the future.

If the charger circuit is not on the backup side, I assume there will be regulatory pushback.

I don't know what the AHJ will require, but its a good bet some automatic safety disconnect is required, like the TEG.
 

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