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Questions to ask electrician before ordering

SkyDog

Member
Aug 24, 2021
34
23
New Jersey
I'm considering getting a Model Y LR. I'd be charging it outdoors next to a garage that's about 60' from my house, maybe close to 100' or wiring from the house electric panel to where I would charge the EV. It's and old house & garage. The wiring up to and including the panel is new, but past that it's questionable. The panel is 200 amps (I think).

I'm looking for advice on what I should be asking an electrician who is coming out to give me some estimates. The things I can think of are:
  1. Is the current 120V wiring to the garage good enough for charging an EV or will I start a fire?
  2. can the current 120V / 15 amp line be changed to 120v / 20 amp? (which might be all I really need)
  3. what would it cost to run 240volts out to the garage and what's the most amps that circuit could handle, considering everything else in my house
  4. assuming my wiring isn't useful as it currently is (old, maybe not up to code), I think I'd need estimates for:
    1. running a 120v / 20 amp circuit out there - NEMA 5-20
    2. running 240v / 50 amp (or less amperage if I can't do 50) - NEMA 14-50 or NEMA 6-50
    3. running 240v / highest amperage and hard-wiring a Tesla wall connector

Does the above make sense and is there anything else I should ask?
 
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brkaus

Well-Known Member
Jul 8, 2014
8,079
6,644
Austin, TX
Unless they oversized it, you cannot convert the 120v 15a to 20a safely.

the car should charge on it the 120v 15a and set itself to a safe current draw. If the wiring is old, might have it inspected. It will be slow, but depending on how many miles you drive it may be ok.

it should cost roughly the same cost to install 120v 20a as it would to install 240v 20a. It would use the same wire, just different breakers and outlet.

Prices will vary greatly by job and location, best to get 2-3 quotes. For example, are you trenching through rock, reusing an existing conduit, or an aerial feed.

you are definitely on the right track to consider your driving habits and price out options from big to small and pick.
 
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glide

Active Member
Jun 6, 2018
3,779
5,301
USA
I'm considering getting a Model Y LR. I'd be charging it outdoors next to a garage that's about 60' from my house, maybe close to 100' or wiring from the house electric panel to where I would charge the EV. It's and old house & garage. The wiring up to and including the panel is new, but past that it's questionable. The panel is 200 amps (I think).

I'm looking for advice on what I should be asking an electrician who is coming out to give me some estimates. The things I can think of are:
  1. Is the current 120V wiring to the garage good enough for charging an EV or will I start a fire?
  2. can the current 120V / 15 amp line be changed to 120v / 20 amp? (which might be all I really need)
  3. what would it cost to run 240volts out to the garage and what's the most amps that circuit could handle, considering everything else in my house
  4. assuming my wiring isn't useful as it currently is (old, maybe not up to code), I think I'd need estimates for:
    1. running a 120v / 20 amp circuit out there - NEMA 5-20
    2. running 240v / 50 amp (or less amperage if I can't do 50) - NEMA 14-50 or NEMA 6-50
    3. running 240v / highest amperage and hard-wiring a Tesla wall connector

Does the above make sense and is there anything else I should ask?
Here’s one thing you shouldn’t bring up; don’t tell them you are using the outlet for a Tesla.
 
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jcanoe

Active Member
Oct 2, 2020
3,418
3,467
Maryland
Since you state you would be charging outdoors the best option would be to install a hard wired charging station, i.e a Tesla Wall Connector on the side of the garage. Anytime you have an outdoor receptacle and plug arrangement it is less than ideal as water can get into the connection and cause corrosion over time. The Tesla Wall Connector is designed for outdoor installation where it can get wet in the rain, snow etc.

You could ask for a sub panel to be installed in the garage. This could be as little as 50A or as much as 100A depending on your needs. When installing a sub panel an electrician can use aluminum wire which costs much less per foot than copper wire. (In most cases you can't use aluminum wire to wire a receptacle but you can use aluminum wire for a sub panel.) When dealing with 100 ft run this could save you quite a bit.

The Tesla Wall Connector can be installed, configured on any circuit rated between 15A and 60A so you can match the circuit to your home's additional capacity and your daily charging needs.

Expect this installation to be expensive because it is likely that a trench will have to be dug and a conduit buried for the wire run between the house and the garage.
 

SkyDog

Member
Aug 24, 2021
34
23
New Jersey
the car should charge on it the 120v 15a and set itself to a safe current draw. If the wiring is old, might have it inspected. It will be slow, but depending on how many miles you drive it may be ok.

it should cost roughly the same cost to install 120v 20a as it would to install 240v 20a. It would use the same wire, just different breakers and outlet.

Prices will vary greatly by job and location, best to get 2-3 quotes. For example, are you trenching through rock, reusing an existing conduit, or an aerial feed.

Typical car usage for me is 30-50 miles a few times per week. Maybe a 100-120 mile trip a few times per month. I think 120v charging would work for me, but I'd go with 240v if my current wiring isn't good enough.
Current wiring is an underground conduit - based on other experiences with my old house, it's probably not up to code and a new trench will probably need to be dug.

Here’s one thing you shouldn’t bring up; don’t tell them you are using the outlet for a Tesla.

Was planning to say there's an EV in my future but I haven't decided which - which is actually true.
I want to price a NEMA 14-50 outlet because that should(?) give me the most flexibility for charging any EV.

Since you state you would be charging outdoors the best option would be to install a hard wired charging station, i.e a Tesla Wall Connector on the side of the garage. Anytime you have an outdoor receptacle and plug arrangement it is less than ideal as water can get into the connection and cause corrosion over time. The Tesla Wall Connector is designed for outdoor installation where it can get wet in the rain, snow etc.

You could ask for a sub panel to be installed in the garage. This could be as little as 50A or as much as 100A depending on your needs. When installing a sub panel an electrician can use aluminum wire which costs much less per foot than copper wire. (In most cases you can't use aluminum wire to wire a receptacle but you can use aluminum wire for a sub panel.) When dealing with 100 ft run this could save you quite a bit.

The Tesla Wall Connector can be installed, configured on any circuit rated between 15A and 60A so you can match the circuit to your home's additional capacity and your daily charging needs.

Expect this installation to be expensive because it is likely that a trench will have to be dug and a conduit buried for the wire run between the house and the garage.

Thank you, the information about sub panels and aluminum wiring is very useful. I don't know much about this stuff.

If I do get the Model Y, I'm leaning towards getting the Tesla Wall Connector - it can go under a big roof overhang, and I can even add another small roof if that overhang doesn't turn out to be enough. If I went with a NEMA 14-50 outlet instead, or even just a 120v outlet, I'd put that inside the garage and run the cord out a window, which should be safe, but a little kludgy.
 

jcanoe

Active Member
Oct 2, 2020
3,418
3,467
Maryland
Typical car usage for me is 30-50 miles a few times per week. Maybe a 100-120 mile trip a few times per month. I think 120v charging would work for me, but I'd go with 240v if my current wiring isn't good enough.
Current wiring is an underground conduit - based on other experiences with my old house, it's probably not up to code and a new trench will probably need to be dug.



Was planning to say there's an EV in my future but I haven't decided which - which is actually true.
I want to price a NEMA 14-50 outlet because that should(?) give me the most flexibility for charging any EV.



Thank you, the information about sub panels and aluminum wiring is very useful. I don't know much about this stuff.

If I do get the Model Y, I'm leaning towards getting the Tesla Wall Connector - it can go under a big roof overhang, and I can even add another small roof if that overhang doesn't turn out to be enough. If I went with a NEMA 14-50 outlet instead, or even just a 120v outlet, I'd put that inside the garage and run the cord out a window, which should be safe, but a little kludgy.
I charged my Chevy Volt using 120V, 8 amp and 120V, 12 amp charging. After a few months I was able to install a 240V circuit and never looked back.

120V/8A (this was the Volt's default 120V charging setting) was adequate if I drove ~30 miles per day using the Volt's battery and the rest on gas. I was able to charge at 120V and 12A by using a 20A circuit. This was fine for ~44 miles per day which actually met my daily EV driving need at the time. More driving than 40 something miles of EV driving and 240V charging is the better option.

I don't think you will find running the charging cable through a window to be satisfactory at night and in the rain and snow. Also, since the charging cable is basically an extension cord passing the charging cable through a wall penetration such as a window is probably not allowed by code (people do all sorts of things that are not to code.)

A 14-50 receptacle would certainly meet your charging needs but don't overlook the potential for installing a 14-30 (240V and 30 amp circuit) instead.

Since you have not decided on whether the Tesla Model Y will be your choice in an EV, some of the other brands come with 240V charging equipment (sometimes hard wired installation is included.)

If you want to see what is probably the widest selection of residential and commercial electric vehicle service equipment see ClipperCreek: ClipperCreek, America's Most Popular EV Charging Station
 
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SkyDog

Member
Aug 24, 2021
34
23
New Jersey
A 14-50 receptacle would certainly meet your charging needs but don't overlook the potential for installing a 14-30 (240V and 30 amp circuit) instead.

I'm sure a 14-30 or even less would be sufficient for my current needs. But if my electric panel could accommodate 14-50, I was thinking I should do that for better future-proofing. Or would a 14-30 cost significantly less than a 14-50?

Since you have not decided on whether the Tesla Model Y will be your choice in an EV, some of the other brands come with 240V charging equipment (sometimes hard wired installation is included.)

If you want to see what is probably the widest selection of residential and commercial electric vehicle service equipment see ClipperCreek: ClipperCreek, America's Most Popular EV Charging Station

Thanks for that link, I had not come across that one yet.
When I talk to the electrician, I won't mention Tesla, I'll just say I want a quote for hard-wiring some generic charging station.

If you have conduit, do you know the size?

I just measured it where it comes out of the ground in the garage - it's a heavy black plastic, 1.25" outside diameter.
 

SkyDog

Member
Aug 24, 2021
34
23
New Jersey
I charged my Chevy Volt using 120V, 8 amp and 120V, 12 amp charging.

A 120v might be fine for most of my daily driving, but from what I understand, it might not be enough in winter. I'm in New Jersey and sometimes get some very cold days in winter. I've read that in very cold weather, a 120v line might just be keeping the battery warm and not adding much to the battery recharge. So I think I'll need 240v / higher amperage. Please correct me if I'm wrong.
 

brkaus

Well-Known Member
Jul 8, 2014
8,079
6,644
Austin, TX
@SkyDog Winter will definitely require more charging. Perhaps 2x of summer. I would put in 240v if at all possible. In general, 120v could do OK charging when cold if you start charging when you return and the battery is warm. If you just plug it in after cold soaking for a while... well...

Yes, I would go with 14-50 (and even pull proper wire to support 60a in the future) if the cost difference isn't that much. I would definitely look to future proof if you have to "dig in" and do something.
 

jcanoe

Active Member
Oct 2, 2020
3,418
3,467
Maryland
A 120v might be fine for most of my daily driving, but from what I understand, it might not be enough in winter. I'm in New Jersey and sometimes get some very cold days in winter. I've read that in very cold weather, a 120v line might just be keeping the battery warm and not adding much to the battery recharge. So I think I'll need 240v / higher amperage. Please correct me if I'm wrong.
Re conduit; depending on how full the conduit is with the current wires you may be able to pull new wire for the charging circuit or else use the existing wire to pull through new wire for a sub panel that would provide 120V and 240V for the charging circuit.

The minimum wire gauge for a 30A circuit such as the 14-30 dryer receptacle is 12 gauge which might be able to be run in the existing conduit. Due to the length the electrician might recommend 10 gauge wire. If you want to install the 14-50 receptacle know that it can be used on both a 50A circuit and a 40A circuit (the 40A option exists if there is not sufficient capacity available for adding a 50A circuit.) The minimum gauge for a 50A circuit is 8 gauge and for a 40A circuit it is 10 gauge. (Note: These wire gauges assume THHN type 90C rated wire not NM-B Romex type wire as you can't bury Romex wire underground in a conduit.)

Here is the reference chart. Do not use the first column as that is for NM-B (Romex). Use the 3rd column for THHN 90C wire.:
Cerrowire Resources - Ampacity Charts

If you are charging on a 120V circuit the maximum available power at 12 amps is 1.44kW, only 960W at 8 amps. When charging using 120V in cold temperatures heating the battery will limit charging and the time to charge at 120V could be extended. If the battery is cold the Tesla vehicle will warm the battery pack to 10C (50F) before charging.

In winter you can help ensure that the battery is warm by starting to charge as soon as you arrive home so that the battery is already warm from driving (although if you have an off-peak rate period that does not start until later in the evening you would be charging during a more expensive rate period.) During the charging session if it is cold enough the Tesla may have to heat the battery while charging.
 
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minnesnowta

Member
Aug 15, 2021
56
90
Minnesota
I want to price a NEMA 14-50 outlet because that should(?) give me the most flexibility for charging any EV.
This is a good idea. The NEMA 14-50 requires a 4-wire cord (6/3 w/ ground) while some hardwired chargers only require 3 wires. One issue with a NEMA 14-50 is that I'm pretty sure code requires the use of a GFCI breaker, while Tesla says to NOT use a GFCI breaker since their chargers have a built-in GFCI. Shouldn't be too big of a deal down the road to swap out the GFCI breaker for a non-GFCI one if you decide to swap out the NEMA 14-50 for a hardwired charger.
 

GRRRR

Member
Apr 25, 2021
9
6
Los Angeles
Tesla provides a list of recommended electricians. ( Find an Electrician ) I used one here in Los Angeles. They were very professional and their price was reasonable. We have a separate garage which required them to run the cable from our main panel under the house( about 100 ft. ) then dig a trench under a small area and then up the garage wall. We have the Tesla wall charger gen 3. The cost was $1500 which included having one of their electricians present when the installation was inspected for permitting which it received.
 
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DayTrippin

Member
Apr 30, 2021
723
709
Jax
The Tesla list is a good place to start. In my situation though they were the high water mark for pricing. So most likely anyone else will come in under their quotes. In my situation, it cost me about half of what one of the Tesla suggested installers quoted. YMMV of course.

As mentioned, don't say the word Tesla when talking to any electricians when getting the quote. This clearly an area where there is a Tesla tax.
 

Sacramento

2021 Tesla Model Y LR AWD
Mar 13, 2021
52
76
Sacramento, CA
Something to keep in mind if you need to run conduit underground– NEC requires the top of PVC conduit to be 18" below the surface of the surrounding ground. Depending on your soil conditions, this might be easy. In my case, it wasn't.

NEC allows the top of PVC conduit to be just 4" below the surface IF YOU COVER IT WITH CONCRETE. I covered about 30' of PVC conduit with about six 60 lb. bags of Quikrete, costing about $4 per sack. So much easier than digging! The building inspector loved it.
 

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number23

New Member
Aug 30, 2021
3
0
Shoreline, WA
The Tesla list is a good place to start. In my situation though they were the high water mark for pricing. So most likely anyone else will come in under their quotes. In my situation, it cost me about half of what one of the Tesla suggested installers quoted. YMMV of course.

As mentioned, don't say the word Tesla when talking to any electricians when getting the quote. This clearly an area where there is a Tesla tax.
I live in a townhouse and the circuit breaker is in the garage. I think I am just fine with getting the NEMA 14-50 and how do I not mention the word Tesla when talking to any electricians? What other "excuse" I can use when installing the NEMA 14-50?
 

jcanoe

Active Member
Oct 2, 2020
3,418
3,467
Maryland
I live in a townhouse and the circuit breaker is in the garage. I think I am just fine with getting the NEMA 14-50 and how do I not mention the word Tesla when talking to any electricians? What other "excuse" I can use when installing the NEMA 14-50?
You should do a load calculation to be sure that there is sufficient capacity for an additional 50A circuit.

The 14-50 receptacle is commonly used with larger RV motor homes.
 

MG535

3SR+ ordered 7/22 (blue/black/19s). EDD 9/10-16
Jul 22, 2021
137
103
NJ USA
I live in a townhouse and the circuit breaker is in the garage. I think I am just fine with getting the NEMA 14-50 and how do I not mention the word Tesla when talking to any electricians? What other "excuse" I can use when installing the NEMA 14-50?
Maybe say you’re getting a Leaf or some other EV?
 

DayTrippin

Member
Apr 30, 2021
723
709
Jax
I just said my son plans to park his RV for a while at my house and needed the NEMA 14-50 for it. Saved me a ton by not saying Tesla anywhere in the quoting process.
 

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