Adding a 2nd Tesla home charger and tapping the wires.

[JerseyMike]

Yeah, I think there are two separate issues.
Under NEC:
One can put a 60A breaker on #6 NM-B
One cannot recalculate the load capacity based on the upsized breaker.

So
One cannot run a 48A charger off of #6 NM-B
But
One can put a 60A breaker on #6 and have a Wall Connector set to 40A charging, which is 50A calculated, which is lower than the 55A rating. Not that the extra 10A of breaker has any benefits.

Can also run 60amp breaker with it set to 44amps max with #6.
My point was that the breaker size is not illegal so as to avoid people getting in conflict with installers.

There are ampacity adjustments for the environment (and multiple current carrying conductors in a raceway). Hot attic vs conditioned space, but I think NM-B starts at the 90C value, and gets derated from there. Ideally, the house construction (vented on insulated attic) makes it a non-factor.

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[turns2stone]

This looks like the perfect thread for my question

• In 2020, I got this Gen 2 Wall Connector installed (new panel, too) with a 60A breaker. Has worked perfectly!
• In 2025, I got Tesla Solar + three Powerwall 3s.
• In 2026, I got a Cybertruck, and will be ordering a UWC soon.
• I have 4 EVs, and the current Gen 2 Wall Connector cord is just a bit too short for comfort.

Questions:

1. Can I add a Gen 3/UWC "down stream" from the Gen 2? I suppose the electrician could wire them up in whatever sequence, just using conduit.
2. Can the UWC load balance with the Gen 2?
3. How will (eventual) PowerShare from my Cybertruck work properly with all this?
4. Should I just give up and rip out the Gen 2 and use a single Gen 3/UWC?

 

[BlueLightning]

Another, be careful, my power bill went up $100 in the past 90 days using my one Tesla charger. Maybe more $$ with elevated gas prices $4 gal resulting more EVs and having to burn more coal to make more energy. lol.

 

[pricedm]

This looks like the perfect thread for my question

• In 2020, I got this Gen 2 Wall Connector installed (new panel, too) with a 60A breaker. Has worked perfectly!
• In 2025, I got Tesla Solar + three Powerwall 3s.
• In 2026, I got a Cybertruck, and will be ordering a UWC soon.
• I have 4 EVs, and the current Gen 2 Wall Connector cord is just a bit too short for comfort.

Questions:

1. Can I add a Gen 3/UWC "down stream" from the Gen 2? I suppose the electrician could wire them up in whatever sequence, just using conduit.

>> Gen 2 and Gen 3 can be on one electric panel if they each have independent circuit breaker. So a 60a (or 40a) for each. No mix and match of the different versions.

1. Can the UWC load balance with the Gen 2?

>> No. See above.

1. How will (eventual) PowerShare from my Cybertruck work properly with all this?

>> eventually with Powerwall. But not yet. Lots of threads here

1. Should I just give up and rip out the Gen 2 and use a single Gen 3/UWC?

>> Maybe. I’m in the same situation. I use my Gen 2 and a mobile connector for concurrent charging. I will eventually get either another Gen 2 to support current charging (at 24A per each of my two Teslas) or two Gen 3; one universal (master) and one non-universal (follower).

 

[turns2stone]

1. Can I add a Gen 3/UWC "down stream" from the Gen 2? I suppose the electrician could wire them up in whatever sequence, just using conduit.

>> Gen 2 and Gen 3 can be on one electric panel if they each have independent circuit breaker. So a 60a (or 40a) for each. No mix and match of the different versions.

1. Can the UWC load balance with the Gen 2?

>> No. See above.

1. How will (eventual) PowerShare from my Cybertruck work properly with all this?

>> eventually with Powerwall. But not yet. Lots of threads here

1. Should I just give up and rip out the Gen 2 and use a single Gen 3/UWC?

>> Maybe. I’m in the same situation. I use my Gen 2 and a mobile connector for concurrent charging. I will eventually get either another Gen 2 to support current charging (at 24A per each of my two Teslas) or two Gen 3; one universal (master) and one non-universal (follower).

Thanks for confirming what I was suspecting.

Although I have an empty slot for an additional 60A breaker, I've seen my total grid power draw hit 36.7 kW (153A) and my panel only supports 200A. This is when I have a Tesla charging, the Powerwalls charging, and a heavy load from the house. So, I don't have the headroom to add another wall charger on its own breaker.

Thoughts on getting two UWCs.. put one in the spot where the Gen 2 is today, and add a master/slave to the right in the picture? That would give me the extra cable length I need, and some flexibility to charge a vehicle parked slightly farther away.

 

[mongo]

Thanks for confirming what I was suspecting.

Although I have an empty slot for an additional 60A breaker, I've seen my total grid power draw hit 36.7 kW (153A) and my panel only supports 200A. This is when I have a Tesla charging, the Powerwalls charging, and a heavy load from the house. So, I don't have the headroom to add another wall charger on its own breaker.

Thoughts on getting two UWCs.. put one in the spot where the Gen 2 is today, and add a master/slave to the right in the picture? That would give me the extra cable length I need, and some flexibility to charge a vehicle parked slightly farther away.

Powershare currently doesn't support group power management. Chaining UWCs on one circuit with Powerwall likely will not be supported either due to potential to overfeed the circuit (60A from panel, 48 from truck).

Adding a UWC on a new breaker may be fine because the Gateway should prevent Powerwalls from overloading the electrical service when charging. Three Powerwall 3s (no expansion batteries) have a combined AC charging limit of 15kW.
Could also use dynamic power management to limit the charge rate on one WC.

 

[JerseyMike]

Thanks for confirming what I was suspecting.

Although I have an empty slot for an additional 60A breaker, I've seen my total grid power draw hit 36.7 kW (153A) and my panel only supports 200A. This is when I have a Tesla charging, the Powerwalls charging, and a heavy load from the house. So, I don't have the headroom to add another wall charger on its own breaker.

Thoughts on getting two UWCs.. put one in the spot where the Gen 2 is today, and add a master/slave to the right in the picture? That would give me the extra cable length I need, and some flexibility to charge a vehicle parked slightly farther away.

I would just switch to Gen 3 and add as many as you want and use power management so that max draw for all chargers is 48amps

I have 3 Gen 3 chargers myself so I don’t even have to worry about where I park

The way to do it (and the way I did it) was change the current single wall charger to a small subpanel box fed with a 60amp breaker and then run as many chargers each with 60amp breaker and then use the Tesla software to setup parameters and max total draw, they will adjust to how many vehicles are charging at a given time

 

[turns2stone]

Powershare currently doesn't support group power management. Chaining UWCs on one circuit with Powerwall likely will not be supported either due to potential to overfeed the circuit (60A from panel, 48 from truck).

Adding a UWC on a new breaker may be fine because the Gateway should prevent Powerwalls from overloading the electrical service when charging. Three Powerwall 3s (no expansion batteries) have a combined AC charging limit of 15kW.
Could also use dynamic power management to limit the charge rate on one WC.

Although a have an empty slot to add another 60A breaker, I've already seen my grid draw hit 153A during peaks... I don't think code or any sane electrician would let me put another wall charger on this panel (200A max).

Unless they'll do it, with a hard limit configured on the wall charger?

I would just switch to Gen 3 and add as many as you want and use power management so that max draw for all chargers is 48amps

I have 3 Gen 3 chargers myself so I don’t even have to worry about where I park

The way to do it (and the way I did it) was change the current single wall charger to a small subpanel box fed with a 60amp breaker and then run as many chargers each with 60amp breaker and then use the Tesla software to setup parameters and max total draw, they will adjust to how many vehicles are charging at a given time

I like this idea, but what do you think about the comment above that PowerShare won't support group power management/chaining UWCs?

 

[JerseyMike]

Although a have an empty slot to add another 60A breaker, I've already seen my grid draw hit 153A during peaks... I don't think code or any sane electrician would let me put another wall charger on this panel (200A max).

Unless they'll do it, with a hard limit configured on the wall charger?



I like this idea, but what do you think about the comment above that PowerShare won't support group power management/chaining UWCs?

Good point about PowerShare

I use a manual interlock to power my house from the 50amp plug in the bed, the CT just replaced my gas generator in this regard

The UWC on PowerShare I believe needs its own dedicated setup and would be a bit more complicated as I think the PowerShare box would have to then feed the whole panel

 

[mongo]

Although a have an empty slot to add another 60A breaker, I've already seen my grid draw hit 153A during peaks... I don't think code or any sane electrician would let me put another wall charger on this panel (200A max).

With everything monitored by the Gateway, it would reduce Powerwall charging current to stay under the limit.
15kW PW charging (now) -> 4kW PW + 11kW EV

 

[hemiarch]

Powershare currently doesn't support group power management. Chaining UWCs on one circuit with Powerwall likely will not be supported either due to potential to overfeed the circuit (60A from panel, 48 from truck).

Adding a UWC on a new breaker may be fine because the Gateway should prevent Powerwalls from overloading the electrical service when charging. Three Powerwall 3s (no expansion batteries) have a combined AC charging limit of 15kW.
Could also use dynamic power management to limit the charge rate on one WC.

How do we know this won’t be supported? Has Tesla said something to this effect? Why not just intelligently prohibit the use of the other charger while PowerShare is happening? If push come to shove for me, I’ll just remove the second charger and then worry about running a second wire under ground basically across my entire house and adding a circuit breaker but my setup has a gen 3 daisychained to a UWC with group power management because it’s was simpler to do it this way. We very infrequently use both at the same time anyway.

 

[mongo]

How do we know this won’t be supported? Has Tesla said something to this effect? Why not just intelligently prohibit the use of the other charger while PowerShare is happening? If push come to shove for me, I’ll just remove the second charger and then worry about running a second wire under ground basically across my entire house and adding a circuit breaker but my setup has a gen 3 daisychained to a UWC with group power management because it’s was simpler to do it this way. We very infrequently use both at the same time anyway.

Tesla could add the software to disable the non-PS WC, but that doesn't address a wiring fault that could pull the combined output of the 60A breaker plus Cybertruck output.
One option might be to subpanel just before the WCs (that still requires group power management or careful charging).

 

[mongo]

Tesla could add the software to disable the non-PS WC, but that doesn't address a wiring fault that could pull the combined output of the 60A breaker plus Cybertruck output.
One option might be to subpanel just before the WCs (that still requires group power management or careful charging).

Although, maybe... if the truck was at the end of the chain...

 

[hemiarch]

Tesla could add the software to disable the non-PS WC, but that doesn't address a wiring fault that could pull the combined output of the 60A breaker plus Cybertruck output.
One option might be to subpanel just before the WCs (that still requires group power management or careful charging).

But that’s also true of the setup as it is now. There is only software standing behind both chargers drawing 48 amps and exceeding the 60amp rating. They appear to trust software enough not to require belt AND suspenders hardware safety. That is the whole point of group power management.
Do you think it’s more complicated because electrons are not flowing in the same direction in the PowerShare scenario?
Has anyone read or heard somewhere that group power management will not support PowerShare?
at this point I’ll take any kind of powerwall 3 support for PowerShare but I’m hoping not to have to reinstall something that I installed exactly the way Tesla instructed.

 

[mongo]

But that’s also true of the setup as it is now. There is only software standing behind both chargers drawing 48 amps and exceeding the 60amp rating. They appear to trust software enough not to require belt AND suspenders hardware safety. That is the whole point of group power management.
Do you think it’s more complicated because electrons are not flowing in the same direction in the PowerShare scenario?
Has anyone one read or heard somewhere that group power management will not support PowerShare?
at this point I’ll take any kind of powerwall 3 support for PowerShare but I’m hoping not to have to reinstall something that I installed exactly the way Tesla instructed.

If the chargers pull more than 60A, the breaker trips.
With a 60A breaker and a 48A both feeding the circuit, you need over 108A before anything trips.

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