Question for home charging install - wire size

[acarney]

New house is being built. They only had one option for an EV pre-wire. It's 100 amp service to a 4 gang box.

I'm planning to install a wall connector as soon as the house is done and I move in. My builder doesn't want to install anything user supplied, I guess they're worried about liability and probably quality/timeline issues. At my meeting on site today they weren't able to provide me with an answer on what wire gauge the 100 amp service would have. I asked to be included in the walkthrough they have with the electrician (next Tue or Thur I think) so hopefully I can ask direct questions to them... but I wanted to get some advice from some people here that have installed them (or maybe are electrical workers!) so I can be as prepared as possible.

What if any problems does anyone foresee? Ideally I would like this all in the wall (since it's brand new construction) and just install the wall connector over the top of the gang box.


Edit: The terminus point for the EV wall connector is about 15 to 20 feet away from my panel and maybe 40 feet from the point where the service enters the house from the utility.

 

[Eric33432]

If it is really a 100 amp circuit, the wire will be either #3 copper or #1/0 aluminum which are both too large to fit in the Tesla Wall Connector terminals. Also if it is aluminum wire, you cannot connect that directly to your TWC. But don't worry if they install AL wire, it is fine for such circuits.

If they use smaller wire, then the circuit will not be good for 100 amps.

The easiest thing to do, and not that expensive, would be to install a small sub panel where the wire is installed to, and then run a 50 or 60 amp circuit to the TWC using a short run of conduit from the sub panel and #8 (50 amp) or #6 (60 amp) THHN/THWN copper wire. You could install a surface mount box right over the box to which this circuit is run to. That circuit would be called a "feeder" not a branch circuit or "service".

Installing a sub panel requires 4 wires: the two 240 volt hot wires, neutral, and ground. If they only run 3 wires, you cannot install a sub panel. Note that the TWC only requires 3 wires, the two 240 volt hot wires and a ground.

Later you might be able to run a second circuit to another TWC, another kind of EVSE, or a NEMA outlet. That would depend on the capacity of your main electric service.

 

[acarney]

Ugh. This is becoming far more stressful than it should. I was as low profile, professional, and clean looking as possible. I also was trying to avoid ripping into walls that were literally days old. They only had one option an “EV Pre-wire” and their management/sales people were… less than familiar with exactly what that option was.

I’m asking to be included during the walk through with their electrician subcontractor “just in case” there were questions with my additions. But really I want to drill down into these questions and see if they can size the wire correctly. I don’t NEED 100 amp. I don’t care if they don’t cut me a discount or anything, I would be fine with 4 AWG run with an appropriate sized breaker.

 

[Eric33432]

Don't stress, it should be OK.

Here is some information that will educate you so you can have a meaningful conversation.:

If they really do install a 100 amp EVSE circuit, the wire will be too large for making connection to the Tesla Wall Connector. Likewise, if it is AL wire, it cannot be directly connected to the TWC.

If you want to keep it simple and not install a sub panel, and the wire is too large, or AL, all that is needed is to connect some short #6 CU wire "pigtails" to whatever wire is installed into the 4 gang box with some polaris connectors. I will give you a link for these. Then just connect these #6 CU wires to the TWC. Be sure to change the circuit breaker to a 60 amp breaker.

In the event the wire they install is not really a 100 amp circuit, here is some info so you know what you are getting. Use the 60˚C column for NM-B (Romex) and the 75˚C column for wire that is run in conduit or MC (metal clad) cable.

And note that even if the wire is not good for 100 amps, as long as it is good for 48 amps (after derating for continuous loads) you can use the TWC for 48 amp charging. If it is smaller than that, then you would have to configure the TWC for whatever wire you do have, and be sure to install the appropriate circuit breaker for that size wire.

All these ratings need to be multiplied by 0.8 when used for continuous loads. For example, a #6 Romex cable needs to be derated from 55 amps to 44 amps, and is therefore not good for a 60 amp circuit breaker and 48 amp charging, whereas #6 THHN wire run in conduit when derated from 65 amps is good for 52 amps continuous, and therefore when derated is fine for a 60 amp breaker and 48 amp charging.

Cerrowire Resources - Ampacity Charts

Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Cerrowire's ampacity chart helps calculate the load requirement for a circuit.

www.cerrowire.com

This connector is a Polaris style connector that can be used to connect larger cable to #6 CU or AL wire to the #6 CU you need to connect to the TWC.

Amazon.com

But, if I really had a 100 amp circuit run to my garage I would install a small sub panel to future proof. That's what I would do, but you do not have to do that. Anyone can come back and do that later, so don't stress out over it!

Good luck and ask any further questions you have.

 

[davewill]

If it is really a 100 amp circuit, the wire will be either #3 copper or #1/0 aluminum which are both too large to fit in the Tesla Wall Connector terminals. Also if it is aluminum wire, you cannot connect that directly to your TWC. But don't worry if they install AL wire, it is fine for such circuits.

If they use smaller wire, then the circuit will not be good for 100 amps.

The easiest thing to do, and not that expensive, would be to install a small sub panel where the wire is installed to, and then run a 50 or 60 amp circuit to the TWC using a short run of conduit from the sub panel and #8 (50 amp) or #6 (60 amp) THHN/THWN copper wire. You could install a surface mount box right over the box to which this circuit is run to. That circuit would be called a "feeder" not a branch circuit or "service".

Installing a sub panel requires 4 wires: the two 240 volt hot wires, neutral, and ground. If they only run 3 wires, you cannot install a sub panel. Note that the TWC only requires 3 wires, the two 240 volt hot wires and a ground.

Later you might be able to run a second circuit to another TWC, another kind of EVSE, or a NEMA outlet. That would depend on the capacity of your main electric service.

You don't think it might turn out to be NM-B 2/3? With an in-wall install, I find it unlikely they are going to run conduit.

OP, it was a smart idea to meet with the electrician. I would not be surprised if he's willing to be more flexible simply because he understands the details better.

If it were me, I'd let them install the 100a circuit, then use a small load center, with a flexible pigtail to the wall connector. Once you have a wall connector and a long cable hanging on the wall, the pigtail just isn't going to be significant....beside it's a garage, not a formal dining room. I can tell you that it's nice to be able to disconnect the EVSE from power without having to go to the main panel. I'd also consider using the rest of the 100a for a 14-50 receptacle, even if you have to use a 40a breaker. It can be handy to be able to plug in a mobile connector if the wall connector breaks for some reason. You could also use it for an RV, welder, etc...

 

[Eric33432]

You don't think it might turn out to be NM-B 2/3? With an in-wall install, I find it unlikely they are going to run conduit.

OP, it was a smart idea to meet with the electrician. I would not be surprised if he's willing to be more flexible simply because he understands the details better.

If it were me, I'd let them install the 100a circuit, then use a small load center, with a flexible pigtail to the wall connector. Once you have a wall connector and a long cable hanging on the wall, the pigtail just isn't going to be significant....beside it's a garage, not formal dining room. I can tell you that it's nice to be able to disconnect the EVSE from power without having to go to the main panel. I'd also consider using the rest of the 100a for a 14-50 receptacle, even if you have to use a 40a breaker. It can be handy to be able to plug in a mobile connector if the wall connector breaks for some reason. You could also use it for an RV, welder, etc...

Yes, of course, 2/3 might very well what is used if it is really a 100 amp circuit. OP seems to have some doubts though. Still too large for the TWC. Sounds like everything is already installed in the wall, so what you say is exactly what I would do, install a surface mount load center then a very short run of conduit with THHN/THWN2 wire to the wall connector, sort of like is shown in this photo, although the box is a Generac load shed device for my generator. But this is kind of what it would look like:

But Op seems to not want to fool with all that, so I tried to give him some ideas on how to just use the circuit for the TWC without anything else.

 

[davewill]

Yes, of course, 2/3 might very well what is used if it is really a 100 amp circuit. OP seems to have some doubts though. Still too large for the TWC. Sounds like everything is already installed in the wall, so what you say is exactly what I would do, install a surface mount load center then a very short run of conduit with THHN/THWN2 wire to the wall connector, sort of like is shown in this photo, although the box is a Generac load shed device for my generator. But this is kind of what it would look like:

View attachment 992990

But Op seems to not want to fool with all that, so I tried to give him some ideas on how to just use the circuit for the TWC without anything else.

It sounds to me like the house is framed, but walls are open, and this circuit is not run, yet. I was picturing an install like this:

Simple and neat without lots of extra conduit.

 

[Eric33432]

It sounds to me like the house is framed, but walls are open, and this circuit is not run, yet. I was picturing an install like this:

Simple and neat without lots of extra conduit.

Now that I read OP again, sounds like the walls are installed ("days old") but the wire is not yet run. If that is the case, he should be able to get any reasonable electrician to run a 4/3 NM-B (they don't make 4/2 NM-B cable) or 6/2 MC branch circuit to the location, but it will either be exposed or they will have to tear into the "days old" walls. If it is run exposed, conduit would look a lot better.

I ran 6/2 MC cable to my other TWC because the run had to go over the garage doors and around the springs and brackets of the doors, which would have been difficult to do with conduit, and unfortunately there is a finished room above the garage so no attic space to run the circuit in. I thought about running the MC to a box near the ceiling, and then conduit down the wall, but in the end just ran the MC all the way since as you say it is a garage not a formal room. That is another Generac load shed device, and then conduit out of the Generac box into the TWC. It just has a large 100 amp rated contactor in the box and some electronics that somehow knows if the generator is overloaded and will shut off in that event.

 

[ATPMSD]

Running 100A wire is gross overkill for a wall connector, however, it is great if you terminate at a sub-panel, as has been suggested. If you have the builder do that you can add a 60A circuit for your wall connector, plus another one later on (using built in power sharing), and still be able to have multiple 120v circuits. Running a circuit from a sub-panel to a wall connector is often an easy DIY project.

 

[acarney]

Framing and roof are complete. Walls are still open. Problem is, it's not a fully custom build, it's from a large regional builder that just has some options that the buyers can select from. They won't let me bring in my own electrician or supply my own equipment. I current don't own "anything" yet since the house and land is still technically owned by them until we close. So... they have these "cookie cutter" options, and appear to be customer focused on allowing flexibility in additions of outlets and locations of them, but if it's outside their options they'll tell me no. (For example, their low volt guy wouldn't fun fiber optic in the wall but will run CAT5/6.)

I'm hoping their electrician will bend a little and understand what my end goal is and adjust what type of wire he uses or how it terminates at the wall point. BUT, that also assumes he has access to the correct wire. They're building six houses in that area right now so I imagine they're on a fairly tight schedule and I doubt the construction manager would be happy if the guy has to come back to my house an additional time because he had to source 4 AWG wire or something. This also all assumes I actually get invited to the walk through with the electrician. Normally that isn't something the customer is invited to. They do a walk through with the construction manager and the low voltage guy and the customer, and then the construction manager does a walk through with any subs that come in for some of the more specialized work if there have been a lot of customer added changes (locations of outlets, requests, etc).

I also ordered a wall connector that hopefully will be here Monday so maybe I can make a copy of the mounting template and leave it stapled in the garage or something so even if they won't install it, they'll know ultimately what I'm installing and that I don't need a large opening in the wall for a sub panel or box, etc.

While the other options WOULD work for me, it'll bug me since I have a chance for it to be "perfect" and new... and after $450k for the house I'll always be annoyed that the garage looks like they just slapped a wall connector on after the fact. (For reference, I plan to paint the garage Tesla red and silver and maybe add a Tesla logo and stuff)

Also, this is way more expensive than I could have made it if I went with an electrician after the fact, and I sucked it up and went with the $2,800 cost for that super nice integrated in the wall look. (It was so expensive because even though the run from the main panel is only 30 feet or less, they had to upgrade the main panel to 320 amp since this is a 100 amp EV Pre wire... again, cookie cutter option, they clearly just think 100 amp should cover ANY and all EVs, and they're not wrong). If I went after the fact and didn't mind if there was metal conduit on the wall or pulled in the wall and then a sub panel and stuff it probably would have been ~$500 to $800 and likely a 200 amp service would have been able to accommodate a 60 amp service for 48 amp charging. So aesthetics do play into my craziness some.. and yes I've already been "lectured" (informed) I'm insane if I go with the 320 amp option since I don't need that just for one EV... it also future proofs the home for high draw devices/toys.

 

[Mrbrock]

Framing and roof are complete. Walls are still open. Problem is, it's not a fully custom build, it's from a large regional builder that just has some options that the buyers can select from. They won't let me bring in my own electrician or supply my own equipment. I current don't own "anything" yet since the house and land is still technically owned by them until we close. So... they have these "cookie cutter" options, and appear to be customer focused on allowing flexibility in additions of outlets and locations of them, but if it's outside their options they'll tell me no. (For example, their low volt guy wouldn't fun fiber optic in the wall but will run CAT5/6.)

I'm hoping their electrician will bend a little and understand what my end goal is and adjust what type of wire he uses or how it terminates at the wall point. BUT, that also assumes he has access to the correct wire. They're building six houses in that area right now so I imagine they're on a fairly tight schedule and I doubt the construction manager would be happy if the guy has to come back to my house an additional time because he had to source 4 AWG wire or something. This also all assumes I actually get invited to the walk through with the electrician. Normally that isn't something the customer is invited to. They do a walk through with the construction manager and the low voltage guy and the customer, and then the construction manager does a walk through with any subs that come in for some of the more specialized work if there have been a lot of customer added changes (locations of outlets, requests, etc).

I also ordered a wall connector that hopefully will be here Monday so maybe I can make a copy of the mounting template and leave it stapled in the garage or something so even if they won't install it, they'll know ultimately what I'm installing and that I don't need a large opening in the wall for a sub panel or box, etc.

While the other options WOULD work for me, it'll bug me since I have a chance for it to be "perfect" and new... and after $450k for the house I'll always be annoyed that the garage looks like they just slapped a wall connector on after the fact. (For reference, I plan to paint the garage Tesla red and silver and maybe add a Tesla logo and stuff)

Also, this is way more expensive than I could have made it if I went with an electrician after the fact, and I sucked it up and went with the $2,800 cost for that super nice integrated in the wall look. (It was so expensive because even though the run from the main panel is only 30 feet or less, they had to upgrade the main panel to 320 amp since this is a 100 amp EV Pre wire... again, cookie cutter option, they clearly just think 100 amp should cover ANY and all EVs, and they're not wrong). If I went after the fact and didn't mind if there was metal conduit on the wall or pulled in the wall and then a sub panel and stuff it probably would have been ~$500 to $800 and likely a 200 amp service would have been able to accommodate a 60 amp service for 48 amp charging. So aesthetics do play into my craziness some.. and yes I've already been "lectured" (informed) I'm insane if I go with the 320 amp option since I don't need that just for one EV... it also future proofs the home for high draw devices/toys.

Another option would be to return the new HPWC you ordered and find a new/used Gen 2 on eBay (or on here). It will handle the wire as long as it is copper. You won't be able to use the full range of amps available but it would solve your problem of being as flush as possible (as long as they don't use aluminum).

 

[brkaus]

If it’s really 100a, I’d do something like post #7 above, but with a small sub-panel.

Square D QO 100 Amp 8-Space 16-Circuit Indoor Flush Mount Main Lug Load Center with Cover, Door QO816L100DF - The Home Depot

The Square D QO 100 Amp 8-Space 16-Circuit Fixed Main Lugs Indoor Load Center is UL listed for residential, commercial and industrial power distribution. This load center is built with a rugged themoplastic

www.homedepot.com

Amy electrician should be able to easily come in a flush mount a box where the wire terminates.

I’d gladly pay extra for 320a service! Even if I had to have someone in to finish it. My house is so underpowered.

 

[Eric33432]

Framing and roof are complete. Walls are still open. Problem is, it's not a fully custom build, it's from a large regional builder that just has some options that the buyers can select from. They won't let me bring in my own electrician or supply my own equipment. I current don't own "anything" yet since the house and land is still technically owned by them until we close. So... they have these "cookie cutter" options, and appear to be customer focused on allowing flexibility in additions of outlets and locations of them, but if it's outside their options they'll tell me no. (For example, their low volt guy wouldn't fun fiber optic in the wall but will run CAT5/6.)

I'm hoping their electrician will bend a little and understand what my end goal is and adjust what type of wire he uses or how it terminates at the wall point. BUT, that also assumes he has access to the correct wire. They're building six houses in that area right now so I imagine they're on a fairly tight schedule and I doubt the construction manager would be happy if the guy has to come back to my house an additional time because he had to source 4 AWG wire or something. This also all assumes I actually get invited to the walk through with the electrician. Normally that isn't something the customer is invited to. They do a walk through with the construction manager and the low voltage guy and the customer, and then the construction manager does a walk through with any subs that come in for some of the more specialized work if there have been a lot of customer added changes (locations of outlets, requests, etc).

I also ordered a wall connector that hopefully will be here Monday so maybe I can make a copy of the mounting template and leave it stapled in the garage or something so even if they won't install it, they'll know ultimately what I'm installing and that I don't need a large opening in the wall for a sub panel or box, etc.

While the other options WOULD work for me, it'll bug me since I have a chance for it to be "perfect" and new... and after $450k for the house I'll always be annoyed that the garage looks like they just slapped a wall connector on after the fact. (For reference, I plan to paint the garage Tesla red and silver and maybe add a Tesla logo and stuff)

Also, this is way more expensive than I could have made it if I went with an electrician after the fact, and I sucked it up and went with the $2,800 cost for that super nice integrated in the wall look. (It was so expensive because even though the run from the main panel is only 30 feet or less, they had to upgrade the main panel to 320 amp since this is a 100 amp EV Pre wire... again, cookie cutter option, they clearly just think 100 amp should cover ANY and all EVs, and they're not wrong). If I went after the fact and didn't mind if there was metal conduit on the wall or pulled in the wall and then a sub panel and stuff it probably would have been ~$500 to $800 and likely a 200 amp service would have been able to accommodate a 60 amp service for 48 amp charging. So aesthetics do play into my craziness some.. and yes I've already been "lectured" (informed) I'm insane if I go with the 320 amp option since I don't need that just for one EV... it also future proofs the home for high draw devices/toys.

I understand you are concerned with aesthetics, and don't want anything complicated.

Since they are upgrading you to 400/320 amp service, I say let them install the 100 amp circuit to the garage. You are paying for that, and you might as well get what you will pay for. 5 or 10 or 20 years from now, you (or someone) might really appreciate that you have that 400/320 amp service and 100 amp circuit in the garage. And $2,800 for that now is a good deal and everything will be concealed in the wall.

For now just have an electrician attach some #6 pigtails to that 100 amp circuit to connect it to the wall connector, and replace the circuit breaker with a 60 amp standard breaker and be done with it.

It will sit like that, or some day you (or someone) can use it for a sub panel when ICE cars are a thing of the past and you need additional capacity for two or more cars.

Just be sure the wire they install has 4 wires, two hot, one neutral, and one ground. You will not use the neutral for the wall connector, but you will need it for a sub panel.

Good luck, let us know how it goes.

 

[acarney]

I understand you are concerned with aesthetics, and don't want anything complicated.

Since they are upgrading you to 400/320 amp service, I say let them install the 100 amp circuit to the garage. You are paying for that, and you might as well get what you will pay for. 5 or 10 or 20 years from now, you (or someone) might really appreciate that you have that 400/320 amp service and 100 amp circuit in the garage. And $2,800 for that now is a good deal and everything will be concealed in the wall.

For now just have an electrician attach some #6 pigtails to that 100 amp circuit to connect it to the wall connector, and replace the circuit breaker with a 60 amp standard breaker and be done with it.

It will sit like that, or some day you (or someone) can use it for a sub panel when ICE cars are a thing of the past and you need additional capacity for two or more cars.

Just be sure the wire they install has 4 wires, two hot, one neutral, and one ground. You will not use the neutral for the wall connector, but you will need it for a sub panel.

Good luck, let us know how it goes.

Is attaching pigtails up to code and everything? That is something official and not just a work around home owners take because it's cheap?

I'm leaning towards this being the most elegant solution. I have the future capacity in the wall if I need (even though the main panel is in the garage too, lol) but also have a very nice clean install of the wall connector, like you see in promo pictures and stuff

 

[brkaus]

Yes. Pigtails is fine, as long as a properly rated connection is used (once you know the wire you have). Some were mentioned up-thread.

 

[acarney]

Yes. Pigtails is fine, as long as a properly rated connection is used (once you know the wire you have). Some were mentioned up-thread.

What about if they use aluminum wire? Would I then be able to have an electrician use a pigtail to step down to a smaller AWG and copper?

Also, does everyone think there will be enough space behind the wall connector for all this? Ideally I want to slap the wall connector up right over whatever electric box they leave the cable in so it looks as clean as possible...

https://www.smarthomecharge.co.uk/site/assets/files/2207/tesla_charger_installed_1.png <--- That is ideally what I'm going for (though it'll be in a fully enclosed garage).

I'm really hoping I'll be able to show up and chat with their electrician sub before he starts the work and explain to them. I figure this all should be really pretty easy and something they could accommodate, but it's hard when trying to explain to a construction manager that will later try to explain to the subcontractor and doing it all without physically leaving the device with them to just mount up. I really wish they would just let me supply my own device as long as I have it before electrical is scheduled (so I don't hold up schedules) and sign a disclosure saying that they only warranty that the device is wired correctly, not if it is working etc.

 

[brkaus]

Yes, there are connections, like the Polaris multi tap connectors, that are related for aluminum if they go that route.

 

[Eric33432]

What about if they use aluminum wire? Would I then be able to have an electrician use a pigtail to step down to a smaller AWG and copper?

Also, does everyone think there will be enough space behind the wall connector for all this? Ideally I want to slap the wall connector up right over whatever electric box they leave the cable in so it looks as clean as possible...

https://www.smarthomecharge.co.uk/site/assets/files/2207/tesla_charger_installed_1.png <--- That is ideally what I'm going for (though it'll be in a fully enclosed garage).

I'm really hoping I'll be able to show up and chat with their electrician sub before he starts the work and explain to them. I figure this all should be really pretty easy and something they could accommodate, but it's hard when trying to explain to a construction manager that will later try to explain to the subcontractor and doing it all without physically leaving the device with them to just mount up. I really wish they would just let me supply my own device as long as I have it before electrical is scheduled (so I don't hold up schedules) and sign a disclosure saying that they only warranty that the device is wired correctly, not if it is working etc.

As others have said, pigtails are fine.

I think you mentioned the cable would be run to a 4 gang electrical box. This cable will likely come from the meter not your breaker panel, since you said they are upgrading to 320 amp service.

The 4 gang box will be wider than the Tesla Wall Connector, which has been reported to be able to fit over a two gang box in another post I have seen.

You can splice the pigtails in that box, cover that box with a blank cover, and install the TWC right next to it and just connect the pigtails from that junction box into the TWC, running them inside the wall.

There are other ways to do it also; your electrician will have no problem figuring out what is the best way to do it. But don't be surprised if he or she suggests to install a small sub panel.

 

[Mrbrock]

What about if they use aluminum wire? Would I then be able to have an electrician use a pigtail to step down to a smaller AWG and copper?

Also, does everyone think there will be enough space behind the wall connector for all this? Ideally I want to slap the wall connector up right over whatever electric box they leave the cable in so it looks as clean as possible...

https://www.smarthomecharge.co.uk/site/assets/files/2207/tesla_charger_installed_1.png <--- That is ideally what I'm going for (though it'll be in a fully enclosed garage).

I'm really hoping I'll be able to show up and chat with their electrician sub before he starts the work and explain to them. I figure this all should be really pretty easy and something they could accommodate, but it's hard when trying to explain to a construction manager that will later try to explain to the subcontractor and doing it all without physically leaving the device with them to just mount up. I really wish they would just let me supply my own device as long as I have it before electrical is scheduled (so I don't hold up schedules) and sign a disclosure saying that they only warranty that the device is wired correctly, not if it is working etc.

As far as I can find, aluminum Romex tops out at 2ga which is below 100A when rated for in wall use. This means they will likely use copper since anything else is going to require conduit or running MC or other protected cable through the studs. Romex is by far the easiest solution, especially if studs are already in.

Also, check your PM inbox.

 

[Eric33432]

As far as I can find, aluminum Romex tops out at 2ga which is below 100A when rated for in wall use. This means they will likely use copper since anything else is going to require conduit or running MC or other protected cable through the studs. Romex is by far the easiest solution, especially if studs are already in.

Also, check your PM inbox.

But they could run 1-1-1-3 AL SE cable for a 100 amp branch circuit or feeder to a sub panel. SE is rated for 75˚C starting in the 2017 NEC.

Amazon.com

AL is fine if it is connected to CU pigtails with split bolts or Polaris connectors that are designed for AL / CU wire.

If they are installing 320 amp service, it is very likely the 100 amp circuit for the EVSE will not be run to your main load center. The whole idea of the 320 service is to give you more than 200 amps. Very likely, there will be a "meter-main" installed, and from that they will run a 200 amp feeder to your main panel that you said is in the garage, and a separate 100 amp circuit/feeder for the EVSE. It will be a "branch circuit" if it terminates directly into the EVSE and it will be a "feeder" if it terminates into a sub panel. This will be superior to just having 200 amp service, and you should let them do it, and the price you discussed is very good. It is always easiest to do these kinds of things when the house is being built.