Wiring for an EV charger - advice needed

[DayDreaming]

I'm looking for opinions / advice on getting ready for my first EV - a Tesla Model Y LR. I need to get some electrical work done for recharging the EV, and estimates I've gotten were a lot more than I expected.

Currently: old house with fairly new 100 amp main panel in the unfinished basement. There is room in the panel to add a 50 amp breaker. I'd be charging the car outside of a small detached garage, about 70' from the house, currently has 2 120v 15 amp lines running to it. The 120v lines run underground but they were run through well piping, not electrical conduit, so definitely not up to code. I don't have a big electric load in the house so I've been told that a 50amp circuit for the EV would not be a problem.

What I want: the garage if more like a small old barn, too small to easily park a car inside. So I'd be charging the car outside. I'm thinking I should get a Tesla Wall Connector mounted on the outside of the garage. There's a big roof overhang on one side, so I could park under there to be out of the weather and have the Connector mounted there. I know that some people charge their EVs on 120v but my understanding is that that is really slow and almost unworkable on really cold days, so I definitely need a 240v line and that's where the big expense comes in.

I've had a few electricians out, and 2 of the quotes are around $5k which includes

• 70' trenching and wiring from house to garage
• add 50 amp sub panel to garage with 30 (or 40?) amp circuit for charging
• wire the Tesla Wall Connector (which I purchase)
• permits and fees

Lowest estimate is around $3,600 which includes trenching and wiring the Connector directly to a 50 amp dedicated circuit - no sub panel in the garage. In this estimate, the trenching alone is $1800 and he said if I do that myself, the electric work would be only $1800.

On thing I'd like opinions on is having the Tesla wall connector direct wired on it's own circuit from the main panel vs adding a sub panel to the garage had running it off that. There are 2 exiting 120v lines to the garage, but one is for an outside light that's on a 2-way switch so I can turn it on from inside the house. The other 120v 15 amp line powers a few outlets and lights. 2 electricians said the sub panel gives me more flexibility for future needs, the other guy said I really should charge an EV on it's own dedicated circuit.

Also wondering if anyone has dug their own trench for electric conduit. If I let the electricians do this, then it's their job to fix anything else they might break - like damaging the exiting 120v lines, or the septic line. If I dig the trench, then that's my problem. My soil is clay with big rocks so I know it won't be easy, so I'm not sure if it's worth the $1800 savings.

Anything else I should be considering?

 

[MRG]

You definitely need a 240 connection to charge your Tesla. Yeah 120v works in an emergency but you'll only add 3-4 miles of range per hour of charging. A NEMA 14-50 would work but it's a only a small amount of your cost. I'd just let the electrician trench and run the sub. Is there still a federal tax rebate for a charging station this year? Your Tesla wall charger needs Wi-Fi do you have good signal for it?

 

[folivier]

One possibility is to utilize the 2 existing 15 amp 120 volt lines but make sure they are on separate legs at your breaker box. Not difficult to do that, just move the breaker so that it grabs the other leg. Then at the shed add a subpanel for those 2 wires. That would give you 240 volts at 15 amps for your receptacle.

 

[zinger1457]

Being the DYI type I would look at hiring someone to dig a new trench (to code) and I would run new cabling (to code) for both the old 120V lines and the new 240V lines. The old 120V lines could be a problem if you ever sold the house, good time to correct that. Check local code but usually as long as the trench is deep enough it doesn't need to be in conduit. Then hire an electrician to make the connections at both ends and verify everything is correct.

 

[TriumphTR3fan]

I'm looking for opinions / advice on getting ready for my first EV - a Tesla Model Y LR. I need to get some electrical work done for recharging the EV, and estimates I've gotten were a lot more than I expected.

Currently: old house with fairly new 100 amp main panel in the unfinished basement. There is room in the panel to add a 50 amp breaker. I'd be charging the car outside of a small detached garage, about 70' from the house, currently has 2 120v 15 amp lines running to it. The 120v lines run underground but they were run through well piping, not electrical conduit, so definitely not up to code. I don't have a big electric load in the house so I've been told that a 50amp circuit for the EV would not be a problem.

What I want: the garage if more like a small old barn, too small to easily park a car inside. So I'd be charging the car outside. I'm thinking I should get a Tesla Wall Connector mounted on the outside of the garage. There's a big roof overhang on one side, so I could park under there to be out of the weather and have the Connector mounted there. I know that some people charge their EVs on 120v but my understanding is that that is really slow and almost unworkable on really cold days, so I definitely need a 240v line and that's where the big expense comes in.

I've had a few electricians out, and 2 of the quotes are around $5k which includes

• 70' trenching and wiring from house to garage
• add 50 amp sub panel to garage with 30 (or 40?) amp circuit for charging
• wire the Tesla Wall Connector (which I purchase)
• permits and fees

Lowest estimate is around $3,600 which includes trenching and wiring the Connector directly to a 50 amp dedicated circuit - no sub panel in the garage. In this estimate, the trenching alone is $1800 and he said if I do that myself, the electric work would be only $1800.

On thing I'd like opinions on is having the Tesla wall connector direct wired on it's own circuit from the main panel vs adding a sub panel to the garage had running it off that. There are 2 exiting 120v lines to the garage, but one is for an outside light that's on a 2-way switch so I can turn it on from inside the house. The other 120v 15 amp line powers a few outlets and lights. 2 electricians said the sub panel gives me more flexibility for future needs, the other guy said I really should charge an EV on it's own dedicated circuit.

Also wondering if anyone has dug their own trench for electric conduit. If I let the electricians do this, then it's their job to fix anything else they might break - like damaging the exiting 120v lines, or the septic line. If I dig the trench, then that's my problem. My soil is clay with big rocks so I know it won't be easy, so I'm not sure if it's worth the $1800 savings.

Anything else I should be considering?

Congratulations on joining the transition to EV transportation. Once you get past this project your costs at home will be minimal.
We bought our EV just before the pandemic & installed 220 volt outlets inside & outside our garage which is also where our electric panel is located.
Most homes today are built with 200 amp service. 100 amps seems small so you may want a sub panel. 50 amps for your EV should be sufficient unless you plan to charge two or more vehicles. What you need are outlets that will support 220 volt electric supply. NEMA 14-50 is considered the standard. This will allow you to charge at a rate of around 29 miles per hour. You don’t need the Tesla wall connector unless you want to charge at a somewhat higher rate of about 44 miles per hour. The car actually has the charger internally. The wall connector is actually electric vehicle supply equipment ( EVSE ). Not getting the wall connector will save over $500.00 with not much reduction in charge speed. Even a completely discharged battery (which has never happened with us) will charge overnight.
When we decided to buy our Tesla the sales advisor told us we probably wouldn’t need it. Most owners charge overnight & the extra speed isn’t necessary.
The car comes with a universal mobile connector (UMC) that uses several different interchangeable AC plugs. However, it is only delivered with the 120 volt plug. Go to the Tesla website and order the 220 plug. It cost us about $35.00, a minimal expense for the increase in speed.
120 volts will work but it is sloooow. It will charge your car at about 4 mph. The only time we use it is when we stay at a relatives house when we are on a vacation & don’t use the car often.
Others can comment better about running the line to your garage but I think that code requires that the line be dedicated for a single outlet.
You can find more information on the Tesla Motors Club forum about EVSE installation.
Enjoy your new ride!
P.S. There’s an EV charging expert in your state that has many useful videos about EVSE on YouTube. His name is Tom Moloughney & his channel is “ A State Of Charge “. You may want to watch & contact him.

 

[DayDreaming]

... Is there still a federal tax rebate for a charging station this year? Your Tesla wall charger needs Wi-Fi do you have good signal for it?

Yes - federal tax credit for 30% the cost of a home charging station, up to $1000.
My phone picks up home wi-fi by the garage, not a strong signal but works for the phone.

One possibility is to utilize the 2 existing 15 amp 120 volt lines but make sure they are on separate legs at your breaker box. Not difficult to do that, just move the breaker so that it grabs the other leg. Then at the shed add a subpanel for those 2 wires. That would give you 240 volts at 15 amps for your receptacle.

I can't really do that because 1 of the 120v lines is wired for a 2-way switch so I can turn on an outside light on the garage from my house. I'd rather leave that as is.

Being the DYI type I would look at hiring someone to dig a new trench (to code) and I would run new cabling (to code) for both the old 120V lines and the new 240V lines. The old 120V lines could be a problem if you ever sold the house, good time to correct that. Check local code but usually as long as the trench is deep enough it doesn't need to be in conduit. Then hire an electrician to make the connections at both ends and verify everything is correct.

I might be able to hire a neighbor to help with the trench, I still worry about hitting any existing wires.

...You don’t need the Tesla wall connector unless you want to charge at a somewhat higher rate of about 44 miles per hour. ...
P.S. There’s an EV charging expert in your state that has many useful videos about EVSE on YouTube. His name is Tom Moloughney & his channel is “ A State Of Charge “. You may want to watch & contact him.

I wanted the Tesla Wall Connector instead of an outside plug because it's weather proof. I know that people use outdoor receptacles with weatherproof covers but I feel more comfortable with the wall charger and it's a small part of the cost of this project. Thanks for the tip on the Youtube channel, somehow I didn't come across that one yet!

 

[Scrapr]

I might be able to hire a neighbor to help with the trench, I still worry about hitting any existing wires.

you can hire a Locate service to find underground wires & supply lines. Typically (here) they are free. That may only be in right of ways and not private property. Your electrician will hire one before he hires out trenching. I'd do it myself with a rental trencher delivered to my job

 

[ERD50]

One possibility is to utilize the 2 existing 15 amp 120 volt lines but make sure they are on separate legs at your breaker box. Not difficult to do that, just move the breaker so that it grabs the other leg. Then at the shed add a subpanel for those 2 wires. That would give you 240 volts at 15 amps for your receptacle.

I was also thinking about this. OP said one is wired to a light switch, but that could be bypassed and use some kind of wireless switch for the lights.

Question for the EV owners: Can the Tesla be programmed to draw only X amps (I think so?)?

First, circuits are only rated for 80% for a continuous load (anything over 3 hours), so that's 12A for a 15A circuit. At 230V and 12A, that's ~ 2.7 kW, so rough number of charging from say 20% to 80% on 100 kWh pack would be 60 kWh/2.7kW = 22 hours. Not great, but workable for charging most nights since your daily driving would not normally be taking you down that far (I assume).

As mentioned earlier, these would need to be on separate phases, I don't think the Tesla can work with two 120V sources paralleled. On separate phases, the voltages add to ~ 230V.

Second, with 100A service, tapping 30, 40, or 50A for the car alone sure seems iffy to me.

But I'd also be thinking about bringing everything up to code. That old non-code wiring will be seeing a lot of continuous use. I'd feel a little shaky relying on it.

-ERD50

 

[OldShooter]

Being the DYI type I would look at hiring someone to dig a new trench (to code) and I would run new cabling (to code) for both the old 120V lines and the new 240V lines. The old 120V lines could be a problem if you ever sold the house, good time to correct that. Check local code but usually as long as the trench is deep enough it doesn't need to be in conduit. Then hire an electrician to make the connections at both ends and verify everything is correct.

I agree with this and would add the suggestion that you go as heavy on the run as is feasible, maybe 60 amps. When we gutted and remodeled I put a 60 amp sub-panel in the attached garage, primarily for a welder. It has slowly accreted additional breakers and circuits. Going without a sub-panel is something you will regret, IMO.

...I might be able to hire a neighbor to help with the trench, I still worry about hitting any existing wires. ...

Do NOT dig without calling the locating service. In our state it's free, too. It's not only wires you might hit. Water and gas are under there somewhere. Possibly telephone too. The locating service will put color-coded flags on everything. If you are anywhere a flagged route, hand dig and very carefully -- like porcupines make love.

 

[pb4uski]

Is there enough room in the existing underground conduit (the well piping) to accomodate a wire for your lights and a new wire for the EV charger? If so, I would use one of those wires to pull through a larger wire for the EV charger and declare victory.

Or substitute one wire for the two and add a subpanel at the garage to split the circuit to your light and the EV charger.

Idea is that since so much of the cost is trenching to try as best as possible to repurpose the existing conduit even though it isn't up to today's codes.

 

[DayDreaming]

you can hire a Locate service to find underground wires & supply lines. Typically (here) they are free. That may only be in right of ways and not private property. Your electrician will hire one before he hires out trenching. I'd do it myself with a rental trencher delivered to my job

I will definitely do that if I dig the trench myself. I've been looking at https://call811.com/ for this. It's very very unlikely that there are any public utilities underground on my property - there aren't any underground utilities around here at all. I'm more worried about my own underground electric, septic and well - it's not clear to me if the 811 service would identify these.

Question for the EV owners: Can the Tesla be programmed to draw only X amps (I think so?)?

First, circuits are only rated for 80% for a continuous load (anything over 3 hours), so that's 12A for a 15A circuit. At 230V and 12A, that's ~ 2.7 kW, so rough number of charging from say 20% to 80% on 100 kWh pack would be 60 kWh/2.7kW = 22 hours. Not great, but workable for charging most nights since your daily driving would not normally be taking you down that far (I assume).

As mentioned earlier, these would need to be on separate phases, I don't think the Tesla can work with two 120V sources paralleled. On separate phases, the voltages add to ~ 230V.

Second, with 100A service, tapping 30, 40, or 50A for the car alone sure seems iffy to me.

But I'd also be thinking about bringing everything up to code. That old non-code wiring will be seeing a lot of continuous use. I'd feel a little shaky relying on it.
-ERD50

I'm not a Tesla owner until I actually get the car but I've been reading a lot. Yes, you can set the car to limit how many amps it uses in recharging. And it would further limit the amount of current it draws if it detects problems with the power coming in.

In the Tesla forums, I've seen recommendations against trying to combine 2 120v lines into 1 so I'm not even going to considering that. I want to get a proper 240v line out to the garage.

I was worried about this at first, but 3 electricians have told me that there's no problem putting a 50 amp sub panel in the garage even tough I only have 100 amps on the main panel. Of course I can't run everything at once or else I'd trip a breaker, but that shouldn't be a problem - my current electric usage is pretty low. Maybe using my electric oven while charging the car would be a problem, but I'll probably set the car to only charge at night when the only thing running might be the fridge.

I agree with this and would add the suggestion that you go as heavy on the run as is feasible, maybe 60 amps. When we gutted and remodeled I put a 60 amp sub-panel in the attached garage, primarily for a welder. It has slowly accreted additional breakers and circuits. Going without a sub-panel is something you will regret, IMO.

Do NOT dig without calling the locating service. In our state it's free, too. It's not only wires you might hit. Water and gas are under there somewhere. Possibly telephone too. The locating service will put color-coded flags on everything. If you are anywhere a flagged route, hand dig and very carefully -- like porcupines make love.

I think I'm leaning towards going with a sub panel. Even if I don't need it now, it's better for future expansion, and I intend to live here for a long time so the extra $$ would well spent I think. Definitely agree on the 811 locating service, I just need to find out if they'll mark my own underground electric, well and septic. My septic pipes run to a different corner of the yard so should not be a problem, but the well and existing 120v underground lines - who knows.

 

[DayDreaming]

Is there enough room in the existing underground conduit (the well piping) to accomodate a wire for your lights and a new wire for the EV charger? If so, I would use one of those wires to pull through a larger wire for the EV charger and declare victory.

Or substitute one wire for the two and add a subpanel at the garage to split the circuit to your light and the EV charger.

Idea is that since so much of the cost is trenching to try as best as possible to repurpose the existing conduit even though it isn't up to today's codes.

I'll be getting a permit for this work and I really don't think this would be approved!

 

[ERD50]

...

In the Tesla forums, I've seen recommendations against trying to combine 2 120v lines into 1 so I'm not even going to considering that. I want to get a proper 240v line out to the garage.
....

Just to clarify, I'm not suggesting that you plug into two 120V circuits to charge the Tesla.

But.... a "proper 240V line" is two 120V circuits. That's how you get 240V, you use two 120V circuits that are on different phases (residential US circuits are two phases).

What that means is an electrician can take your two 120V lines (if they are on separate phases which they probably are, or swap one of them at the panel so they are on separate phases), and wire them to a single 240V 15A outlet. With a sub panel, you could also have some 120 V 15 A outlets. That is how all 240V circuits in the US are done.

But that's different than those pigtail type things with two 120V plugs on them - those can be problematic. For one thing, if one circuit breaker blows, the other may still on and the circuit is half-energized. Not safe. A 240V breaker in the panel is wired to open both sides (notice how a physical bar connects the two sides on those 240V double breakers). Some of those adapters may have some safety circuits built in to prevent those problems, but it's probably best to not rely on them for every day use.

-ERD50

 

[pb4uski]

I'll be getting a permit for this work and I really don't think this would be approved!

From what I read, well piping is sturdier since it needs to hold up to water pressure, and it is obviously waterproof, so since it is already there it might be accepted... but you won't know until you ask.

I guess the way I was thinking about it is that if there were room for the wires that you need then I would ask as if they were already in place.... "I already have (description of wire you will need) running to the out building but it is in (dimension) well piping... can I just use that wire?"

If the answer is yes, then pull the new wire yourself... this assumes that you have good access... I know that I do for the conduit for the electrical service between my house and garage... if I needed more or bigger wire for a EV charge in the garage it would be relatively easy to pull more wire through.

When they did my well electrical the contractor did a facinating thing. My well is ~300' from the house (long story). They laid the conduit from the well to the house. Then they had a large ball of heavy kite string up at the well that they tied to a crumpled up piece of newspaper that was much smaller than the conduit diameter and pushed the ball into the conduit. Down that the house, they attached a shop vac to the end of the conduit, turned it on and it only took a few seconds for the string to travel the ~300' through the conduit to the house... in a flash! They then tied the end of the wire to the string and pulled the wire through to the wellhead.

 

[tb001]

Fwiw, the 811 service told us they only marked public utilities, even though their equipment can detect other lines. We learned this after the fact, after hitting a gas line we assumed would have been marked.

It may vary by region, but I’m not sure they would want to take on liability for finding every random line someone may have installed.

 

[tb001]

From what I read, well piping is sturdier since it needs to hold up to water pressure, and it is obviously waterproof, so since it is already there it might be accepted... but you won't know until you ask.

I guess the way I was thinking about it is that if there were room for the wires that you need then I would ask as if they were already in place.... "I already have (description of wire you will need) running to the out building but it is in (dimension) well piping... can I just use that wire?"

If the answer is yes, then pull the new wire yourself... this assumes that you have good access... I know that I do for the conduit for the electrical service between my house and garage... if I needed more or bigger wire for a EV charge in the garage it would be relatively easy to pull more wire through.

When they did my well electrical the contractor did a facinating thing. My well is ~300' from the house (long story). They laid the conduit from the well to the house. Then they had a large ball of heavy kite string up at the well that they tied to a crumpled up piece of newspaper that was much smaller than the conduit diameter and pushed the ball into the conduit. Down that the house, they attached a shop vac to the end of the conduit, turned it on and it only took a few seconds for the string to travel the ~300' through the conduit to the house... in a flash! They then tied the end of the wire to the string and pulled the wire through to the wellhead.

That is so cool!

And I agree, I would do everything possible to use the well conduit if there’s room.

 

[travelover]

Re locating electrical wires already in place, I had to locate wires from my house to the barn to support some digging between the buildings. I rented a device from a local rental shop that worked like crazy and allowed me to pinpoint the exact path. Power needed to be flowing to make it detect the wire.

Re locating septic pipes, when I had my septic field inspected, the guys just use 4 foot metal rods sharpened slightly with a T handle and quickly mapped it out.

I'd also recommend a subpanel be installed if you plan to live there. It makes tapping the power supply so much easier in the future.

 

[DayDreaming]

Re locating electrical wires already in place, I had to locate wires from my house to the barn to support some digging between the buildings. I rented a device from a local rental shop that worked like crazy and allowed me to pinpoint the exact path. Power needed to be flowing to make it detect the wire.

Thanks, I will definitely look into that!

For using the existing well pipe for new wires, the electricians I had out looked at it and immediately said no. Maybe they know it won't pass inspection around here, but I will ask again - that would save quite a bit on this project.

 

[HarveyS]

I'd hire the entire job out. Stones, roots, etc will make trenching a tough job if you've never done it before. And, the electrician will get exactly what he/she wants if they do it themselves.

I'd also consider upgrading the house to 200A. Someday soon you may add A/C to the home and need the service. Also, I'd consider doing whatever electrical work that is required to be able to charge two EV's at the garage at the same time. You may fall in love with EV and buy another! Finally, maybe even run a wire for another wifi router in the garage if the signal needs to be stronger for the charger.

This will all add to resale value of the home.

 

[someguy]

Lots of good discussion here. One option I didn't see mentioned is to use Zigbee or Insteon or another similar system for the "remote" light on the detached building. That would allow you to not require direct wiring for the garage light from the house.

 

[ERD50]

Lots of good discussion here. One option I didn't see mentioned is to use Zigbee or Insteon or another similar system for the "remote" light on the detached building. That would allow you to not require direct wiring for the garage light from the house.

It was mentioned.

I was also thinking about this. OP said one is wired to a light switch, but that could be bypassed and use some kind of wireless switch for the lights.
....

-ERD50

 

[DayDreaming]

I'd hire the entire job out. Stones, roots, etc will make trenching a tough job if you've never done it before. And, the electrician will get exactly what he/she wants if they do it themselves.

I'd also consider upgrading the house to 200A. Someday soon you may add A/C to the home and need the service. Also, I'd consider doing whatever electrical work that is required to be able to charge two EV's at the garage at the same time. You may fall in love with EV and buy another! Finally, maybe even run a wire for another wifi router in the garage if the signal needs to be stronger for the charger.

This will all add to resale value of the home.

Good point on hiring it out. I was thinking it might take me a week to dig and it would be great exercise, but paying to have the trench dug is probably money well spent. I could rent a trenching machine, but if I damage something, then that's on me.

I really don't need more than 100A in the house now, even with adding the EV charger. But I should talk to the electrician about putting in a big (terminology?) line to the garage now, even if I can't currently use it. Then I'll be ready if I ever do get more than 100A to the house. It would make sense to do it now, as long as I don't go too overboard on costs.

For Wi-Fi I was thinking I might need a range extender. I had not considered running another wire to the garage for Wi-Fi - do you think that would be better than a range extender (which I've never had, so no experience there).

 

[DayDreaming]

Lots of good discussion here. One option I didn't see mentioned is to use Zigbee or Insteon or another similar system for the "remote" light on the detached building. That would allow you to not require direct wiring for the garage light from the house.

2 electricians felt that if the 2-way switch on the outdoor light is working (it is), then just leave it alone. Add the new wiring and don't touch the wiring for that switch. But I had been thinking about something more up-to-date like you said. I currently use Amazon Alexa for some home automation and it might be nice to control the outside light with that. I could even get Alexa Echo Auto so when I come home at night I could turn those lights on from in the car. Something to think about, thanks.

 

[someguy]

In terms of extending WiFi range reliably I would rank:

1) Wired to a second access point
2) Mesh network (eg, Netgear Orbi or Eero)
3) Repeater

With #3 being a hugely distant third. Typical WiFi repeaters are garbage, IMO.

I really don't need more than 100A in the house now, even with adding the EV charger. But I should talk to the electrician about putting in a big (terminology?) line to the garage now, even if I can't currently use it. Then I'll be ready if I ever do get more than 100A to the house. It would make sense to do it now, as long as I don't go too overboard on costs.

For Wi-Fi I was thinking I might need a range extender. I had not considered running another wire to the garage for Wi-Fi - do you think that would be better than a range extender (which I've never had, so no experience there).

 

[OldShooter]

... For Wi-Fi I was thinking I might need a range extender. I had not considered running another wire to the garage for Wi-Fi - do you think that would be better than a range extender (which I've never had, so no experience there).

Getting wifi out there depends on a lot of things. Best odds would probably be one of the new "mesh" type routers and extenders. That would probably mean upgrading your router, then an experiment with a mesh extender. There are also many wifi antennas; a directional antenna (usually "yagi" type) hooked to your house system and pointing at the garage might be an option too.

2 electricians felt that if the 2-way switch on the outdoor light is working (it is), then just leave it alone. Add the new wiring and don't touch the wiring for that switch. But I had been thinking about something more up-to-date like you said. I currently use Amazon Alexa for some home automation and it might be nice to control the outside light with that. I could even get Alexa Echo Auto so when I come home at night I could turn those lights on from in the car. Something to think about, thanks.

You can have your cake and eat it too. Leave the existing light alone and just add a controlled light, probably an LED floodlight. Or do what we do and use motion activated LED lights. No need to fiddle with a phone as you are driving up. We have several of these and they work great: https://www.homedepot.com/p/Defiant...-Outdoor-Security-Light-DFI-5982-WH/205937592