FAQ: Home Tesla charging infrastructure Q&A

[FlatSix911]

I've perused this thread and a couple of others and haven't seen this situation addressed so I thought I'd post here. Any and all advice is much appreciated. I'm thinking of installing a NEMA 14-50 receptacle now as I've been hemorrhaging cash lately, what with buying the Tesla and all. I would in all likelihood upgrade to a HPWC later this year. As luck would have it, my garage is on the exact opposite side of the house from the service entrance. Running along the exterior of the house would be a little over 100 feet. I believe my 200A service has headroom for 80A charging, but I'll have an electrician do the math.

I understand that to be ready to install the HPWC I should use at least AWG #3 wire for the run. The problem is that the only 14-50 receptacles I've seen are labeled "Wire Size Range AWG #10 - #4". Is there any way to do this? I'd also like to be able to remove the HPWC and replace it with the NEMA 14-50 if I move in the future.

Another cheaper solution: Run AWG #4 for the NEMA 14-50 and just dial down the future HPWC to 64 Amps.

 

[DiamondDave]

Thanks for the responses!

Your #3 (or larger) run can terminate in a sub panel in your garage. Then you can have a breaker for your 14-50 and the appropriate wire and receptacle.

It did occur to me that I could install a subpanel in the garage, but wouldn't that be similarly expensive to just buying the HPWC? I should have mentioned that I'm not concerned about a backup - there is a supercharger under construction 15 minutes from me that will serve as my backup in case of HPWC failure, power outage, etc. In the unlikely event that the wife gets a Tesla one day as well, I could add a second HPWC on the same circuit, right? So there would be no advantage to a subpanel in this case, would there? Or am I missing something?

Another cheaper solution: Run AWG #4 for the NEMA 14-50 and just dial down the future HPWC to 64 Amps.

I guess 64 A is almost as good as 80. I can use AWG #4 (THWN?) for a 100' + exterior run and an 80 amp breaker in the main panel?

Maybe I should just suck it up and buy the HPWC now...

 

[scaesare]

Thanks for the responses!



It did occur to me that I could install a subpanel in the garage, but wouldn't that be similarly expensive to just buying the HPWC? I should have mentioned that I'm not concerned about a backup - there is a supercharger under construction 15 minutes from me that will serve as my backup in case of HPWC failure, power outage, etc. In the unlikely event that the wife gets a Tesla one day as well, I could add a second HPWC on the same circuit, right? So there would be no advantage to a subpanel in this case, would there? Or am I missing something?



I guess 64 A is almost as good as 80. I can use AWG #4 (THWN?) for a 100' + exterior run and an 80 amp breaker in the main panel?

Maybe I should just suck it up and buy the HPWC now...

A quick amazon trip suggests a 100A subpanel with breakers would run you $80 or so...

 

[tga]

It did occur to me that I could install a subpanel in the garage, but wouldn't that be similarly expensive to just buying the HPWC?

NEC 625.23 requires a lockable disconnecting means on an EVSE >60A, so that pretty much means you need a sub panel or switch in the garage, anyway. You don't need a full subpanel; it could be a single box that takes one duplex breaker. Someone here found lightly used disconnects on ebay for dirt cheap; I'm trying to find the post.

The disciples of Chicken Little here will have an embolism over this suggestion, but... If you're looking to save a bunch of money on the install, run the appropriately sized aluminum wire between your breaker and disconnect (1 ga, I think; I don't have the table handy). Make sure the breaker and disconnect are rated for Al wire, and it is installed with lots of no-ox (not really needed with today's wire, IIRC, but it gives everyone a warm fuzzy), and it will be perfectly safe.

Pretty much every home has Al up to the main breaker, and most homes' subpanels are wired with Al. Properly installed, it's perfectly safe. I'm buying a home that has had Al wire to the range for 40 years, and it looks like new - no signs of heating at either end.

In the unlikely event that the wife gets a Tesla one day as well, I could add a second HPWC on the same circuit, right?

Yes, the latest HPWC can share a circuit, if you connect them together via their data terminals (only the data is daisychained; they each need a dedicated power connection). Either 100A breaker to a subpanel in the garage with multiple 100A breakers, of a 100A breaker to a junction box.

 

[tga]

Someone here found lightly used disconnects on ebay for dirt cheap; I'm trying to find the post.

@Solarguy's post is the one I was looking for: Post Pictures of HPWC Installations (Residential and Commercial)

 

[Solarguy]

@Solarguy's post is the one I was looking for: Post Pictures of HPWC Installations (Residential and Commercial)

Here is a link to the current Square D DU323 100amp disconnects on ebay like to ones I used:

square d du323 | eBay

 

[DiamondDave]

Thanks. I read all these threads then forgot about the local disconnect regulation!

$75 for Solarguy's used industrial panel or the Amazon-sourced $80 subpanel + breakers seems like what I'll have to do. I'll look into Al vs Cu wiring.

 

[DiamondDave]

Here is a link to the current Square D DU323 100amp disconnects on ebay like to ones I used:

square d du323 | eBay

I see, it's just a switch, which is all I really need. Solves both local disconnect and wire size problems because I can use AWG #3 in and something smaller out. If the subpanel is about the same price, though, I think I'd lean in that direction. I would be able to use that for a second power source for a second *someday* HPWC.

 

[brucet999]

I've perused this thread and a couple of others and haven't seen this situation addressed so I thought I'd post here. Any and all advice is much appreciated.

I'm thinking of installing a NEMA 14-50 receptacle now as I've been hemorrhaging cash lately, what with buying the Tesla and all. I would in all likelihood upgrade to a HPWC later this year. As luck would have it, my garage is on the exact opposite side of the house from the service entrance. Running along the exterior of the house would be a little over 100 feet. I believe my 200A service has headroom for 80A charging, but I'll have an electrician do the math.

I understand that to be ready to install the HPWC I should use at least AWG #3 wire for the run. The problem is that the only 14-50 receptacles I've seen are labeled "Wire Size Range AWG #10 - #4". Is there any way to do this? I'd also like to be able to remove the HPWC and replace it with the NEMA 14-50 if I move in the future.

PV-EV's answer doesn't solve the problem of connecting your planned HPWC, since the smaller wire from sub panel to 14-50 would be too small. However, if you were to install a junction box close to the HPWC location , you could then run #3 from your panel right through it to the HPWC. When you move, you could simply pull out the short run of #3 and splice a shot run of #6 for a 14-50 in place of the HPWC and replace the 100A breaker with a 50A.

 

[DiamondDave]

The more time I spend on this forum, the littler I seem to know and the less intelligent I feel!

I googled "junction box" but I don't understand the function. Is it just to hide a connection, say from AWG #3 to AWG #4 wire? Would a junction box satisfy the local disconnect requirement? Or would I need a switch as well?

Also, why wouldn't I be able to replace a short run of #3 with #6 and vice versa from a subpanel for adding/removing the HPWC, replacing the breaker as well, of course?

 

[tga]

PV-EV's answer doesn't solve the problem of connecting your planned HPWC, since the smaller wire from sub panel to 14-50 would be too small. However, if you were to install a junction box close to the HPWC location , you could then run #3 from your panel right through it to the HPWC. When you move, you could simply pull out the short run of #3 and splice a shot run of #6 for a 14-50 in place of the HPWC and replace the 100A breaker with a 50A.

I read his reply as "run a 100A circuit to the garage, terminate it at a sub panel, then install a 50A breaker w/ 6ga to the 14-50. Replace with a 100A and run of 3 ga to the HPWC when installed" - you could leave the 14-50 in place as a backup. Breakers likely count as a disconnect, unless your inspector is being excessively picky.

I googled "junction box" but I don't understand the function. Is it just to hide a connection, say from AWG #3 to AWG #4 wire?

Yes. It's a major no-no to have electrical splices buried in walls or sitting out in the open. Must be inside a junction box (and accessible for repairs - can't cover the box with drywall)

Would a junction box satisfy the local disconnect requirement?

No.

Or would I need a switch as well?

Yes (although breakers in a subpanel might count; see above)

Also, why wouldn't I be able to replace a short run of #3 with #6 and vice versa from a subpanel for adding/removing the HPWC, replacing the breaker as well, of course?

Nothing wrong with that. If you have room in the subpanel for another breaker, you can add the HPWC and leave the 14-50. Remove the HPWC if you move

 

[jerry33]

A quick amazon trip suggests a 100A subpanel with breakers would run you $80 or so...

And even if it was the same cost, which it's not, a subpanel gives you flexibility to add a 120V circuit or two.

 

[DiamondDave]

So seems like the best solution for a situation like mine where you have a long run to the garage and want to be able to swap 14-50 receptacle and HPWC for budget/ future move, etc. is:

Run AWG #3 (or better) for the long run from the main panel to a sub-panel in the garage, which can be 100A.. From the sub-panel you can just do short runs for the 14-50, HPWC, or whatever you need. And if you move, uninstalling the HPWC is easy and the new owners still get the benefit of EV charging in the garage.

Elegant solution. Thanks everyone!

 

[MG1234]

Hello all-

Feel I have learned a lot from this thread and similar ones regarding charging installs, though just enough to be dangerous and each specific example seems to sway me back and forth. So first of all: thank you! I am now posting our specific case asking for thoughts.

I understand many feel NEMA 14-50 or HPWC with 50A is more than adequate, however I am past that decision and sticking with full power HPWC. From reading other threads, I already expect some criticism of not sticking with 50A. I would rather go all in now.

Our home is about 3 years old and has 200A service, though much of that is already used. We have two proposals on hand to install, where both include upgrading from 200A to 400A service (JCP&L/FirstEnergy in NJ). The charger will be in a detached garage, about 100 feet run from service meter.

Proposals are from Precision Tech in NJ, who seems to be relatively pricey though after speaking with several other electricians in the area are the only ones who seemed both competent and interested in the service upgrade.

Note that about $4500 of the cost is for the service upgrade from 200A -> 400A (broken down as $1875 for 200A circuit panel, $1500 400A underground meter pan, $975 200A service disconnect).

Proposal #1 $6800 is to add the additional 200A panel near service meter on house then run 90A in a 2 inch conduit (oversized for future) about 100 feet out to garage direct to HPWC for 72A pull (leaving 110A for future use through existing conduit or otherwise).

Proposal #2 $7600 is to run the additional 200A about 100 feet to detached garage on a separate panel there then run 90 A off that to HPWC (leaving 110A for future use in garage).

Note: garage has separate minimal electric there already from house for garage door opener and lights (no panel)

I understood the electrician was to use #4 copper for proposal #1 which I previously thought was appropriate, however info in this thread seemed to suggest #2 copper would be recommended. Given that, I have already reached out to the electrician asking about the gauge/rationale, as well as what would be used in proposal #2.

My wife and I expect our MX 90D in a few weeks. Leaning toward #2 as we also have 2 Model 3 reservations.

---

How (un)reasonable are the quotes given the necessary service upgrade, distance run, and trenching?

What gauge copper is appropriate in each case?

Is running the 200A service to a panel in the garage now preferred over only running 90A to HPWC then 18+ months from now possibly pulling another 90A through the existing conduit?

I separately came across a thread regarding 277V (rather than 240V) being supported with the new HPWC. Given the service upgrade which is being done, is it worth asking for 277V instead?

Thanks again to all. The collective wisdom here is beyond words.

 

[tga]

I would rather go all in now.

If a full power HPWC is driving a service upgrade to 400A, I would certainly call that "going all in."

Our home is about 3 years old and has 200A service, though much of that is already used.

When you say "much of that is already used", what do you mean? A full breaker panel, or individual breakers totaling 200A or more, does not require more than 200A service.

200A is a lot, even with car charging. Unless you have serious loads in the house (electric heat, pool/spa pumps, big A/C loads, a large house with lots of lighting, etc), 400A is probably not necessary. I know several people with 400A service, and for most of them, it's not necessary - it's really just "bragging rights" (a lot of my friends are Tim Allen/"Home Improvement" fans)

The required size for a service is based on a load calculation, which is a (potentially confusing) calculation of a home's peak needs. You shouldn't need an upgrade, unless someone has done a load calculation (and shown/explained it to you) that demonstrates your potential demand exceeds 200A.

Are you asking for a HPWC installation, and being told the service upgrade is required? Or are you asking for the install and service upgrade? Two very different situations.

Proposal #2 $7600 is to run the additional 200A about 100 feet to detached garage on a separate panel there then run 90 A off that to HPWC (leaving 110A for future use in garage).

Again, installing a 90A breaker for the HPWC in a new 200A panel doesn't leave 110A left - it doesn't work that way. You could install 10 100A breakers in a 200A panel. As long as the total draw doesn't exceed 200A, you're fine.

I understood the electrician was to use #4 copper for proposal #1 which I previously thought was appropriate, however info in this thread seemed to suggest #2 copper would be recommended. Given that, I have already reached out to the electrician asking about the gauge/rationale, as well as what would be used in proposal #2.

It sounds like your electrician isn't well versed in car charging requirements. #4 is undersized for charging at 72A. If charging at 72A, National Electric Code requires you upsize the circuit by 125%, and install wire/breaker for 90A min (circuits are rated for intermittent loads; the NEC considers car charging a continuous load and requires the 125% safety factor). This would require minimum #3 copper or #1 aluminum. #2 copper is often recommended, since #3 copper isn't often used and is harder to find. Bear in mind this wire is also good for a 100A breaker/80A charging - I would install a 100A breaker and set the HPWC to 80A for future expandability, vs unnecessarily limiting it.

My wife and I expect our MX 90D in a few weeks. Leaning toward #2 as we also have 2 Model 3 reservations.

---

How (un)reasonable are the quotes given the necessary service upgrade, distance run, and trenching?

What gauge copper is appropriate in each case?

I can't speak to costs in your area. A 100A circuit is #3 copper/#1 aluminum minimum

Is running the 200A service to a panel in the garage now preferred over only running 90A to HPWC then 18+ months from now possibly pulling another 90A through the existing conduit?

You can't run multiple circuits from the home to a detached outbuilding - NEC requires a single feed with a subpanel in the outbuilding. Even if you could, you'd need to plan ahead an install a larger conduit. Plus, pulling cables through a conduit that isn't empty can be tricky - you would probably want to install a second conduit in the trench for future use.

I separately came across a thread regarding 277V (rather than 240V) being supported with the new HPWC. Given the service upgrade which is being done, is it worth asking for 277V instead?

277V is the nominal line-to-neutral voltage of a 277/480 three phase system. This is heavy-duty commercial/industrial power. It's unlikely that you'd get permits to install this in a residence or that the power company would offer it. You'd probably be looking at 10's of thousands to install, even if you could.

In summary, here's what I would do -

Install a 100A subpanel in the garage, fed with #1 aluminum off a 100A breaker in the main panel. Install a 100A (or 90, but why not 100?) breaker in the subpanel to feed the HPWC. Feed the HPWC with #2 or #3 copper from its subpanel breaker (this is a short run, so cost is less of an issue, and I don't believe the HPWC is rated for Al). When the Model 3's arrive, you can add breakers to the subpanel and add more HPWC's. The newest HPWC can be tied together to share the available charging current.

Only do the service upgrade if a load calculation shows it is needed and the inspector requires it.

Al wire to the subpanel, properly installed and sized, is just as safe as copper, and will save you at least $1000 on a 100 foot run (yes, copper is that expensive).

EDIT: Also, if the load calculations show a service upgrade is needed, consider replacing some heavy electric appliances with gas ones - that will free up some headroom in the calculation, and may be cheaper than a service upgrade.

 

[uidzer0]

Can anyone recommend an alternative to evseadapters.com for a NEMA 6-20P - 5-15R adapter? Had one in my shopping cart from that site for a while, but was waiting on my MX delivery to get scheduled. Now I know the car is in route, but the evseadapters.com site has been down for days.

 

[FlatSix911]

NEMA Plug Adapters, Twist Lock, Locking, Straight Blade, 15A, 20A, 30A

Adapters

 

[TexasEV]

No, neither of those places would have what uidzer0 is asking for. I believe he means the 6-20P to 5-20R adapter that EVSEadapters.com made specifically for Teslas. It's purpose is to use the UMC 5-20 adapter to get 16A charging from a 6-20 outlet and not have to manually turn down the amps as you would with another adapter such as 6-20 to 14-50. Neither of the two vendors listed above makes such a product, and I actually had discussed it with Corddepot who refused to offer one because it's unsafe if it's used for something other than Tesla charging. That's when EVSEadapters.com agreed to start making it with Tesla only labeling.

 

[uidzer0]

Thanks @TexasEV, that's a correct assessment of what I was going for. Thank you @FlatSix911

If EVSEAdaptors.com doesn't com back online in the next week or two, I'm thinking of the following config instead for my NEMA 6-20 outlet:

UMC w/ Tesla's NEMA 5-20 Adapter ==> customavrack.com's L5-20R-L14-20P adapter ==> customavrack.com's L14-20R-NEMA 6-20P ==> wall/outlet

I realize the UMC 5-20 adapter is for 110/120 volt, but it's the amperage I'm trying to address. From what I've read on the forums, voltage doesn't matter with the Tesla 5-x adapters and with the configuration above, I would not have to dial down the charging amperage every time I plugged in the UMC in my garage.

Would appreciate responses from anyone that's done something similar and had safe, successful charging.

 

[Frankman60]

Thanks @TexasEV, that's a correct assessment of what I was going for. Thank you @FlatSix911

If EVSEAdaptors.com doesn't com back online in the next week or two, I'm thinking of the following config instead for my NEMA 6-20 outlet:

UMC w/ Tesla's NEMA 5-20 Adapter ==> customavrack.com's L5-20R-L14-20P adapter ==> customavrack.com's L14-20R-NEMA 6-20P ==> wall/outlet

I realize the UMC 5-20 adapter is for 110/120 volt, but it's the amperage I'm trying to address. From what I've read on the forums, voltage doesn't matter with the Tesla 5-x adapters and with the configuration above, I would not have to dial down the charging amperage every time I plugged in the UMC in my garage.

Would appreciate responses from anyone that's done something similar and had safe, successful charging.

I think EVSEadapters.com is done. Their site has been down for weeks, and no one answers their phone. All calls go to voice mail and I left them many voicemail messages and they have not called me back. I placed an order online with them right before their website went dark and they promptly charged my credit card, and didn't ship the adapter. The other weird thing is that the phone number on their sales invoice is a Utah number, and their business is in California. I guess that might not be completely wacky, but it is worth noting.