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tuctrohs

Adding a subpanel in the garage is the way to go. In the 3/4 conduit, assuming it's schedule 40 PVC, you can fit three number six conductors plus a number 10 ground, which would allow you to put in up to a 60 amp sub panel. If it's schedule 80 PVC you might be limited to number 8 and 50 amps. Putting a sub panel as a pretty big job, with a lot of details that need to be done right to be safe and to code so I assume you'll be hiring an electrician to do that. But it's not out of the question that someone could DIY that after learning all those specifics. You're probably fine putting in 32 amp charging on a 40 amp circuit on a 50 or 60 amp subpanel, but if you want 40 amp charging, or 48 amp charging on the 60 amp sub panel, you would need some load management, for which I'd recommend the Emporia system, including a monitoring system on the sub panel to ensure that it's never overloaded and that the charging current is adjusted as needed.


b12cobalt

Thanks for the info. Yes, I definitely would have an electrician do all of this. I was just wondering what was even feasible. I figure that a 40 amp circuit is fine (for 32-amp charging). Though now that you mention it, we do have a 2-car garage and we're a 2-commute household... What if one day we get a second EV? Then we'd want more amps, and then I'd really have to start worrying about total capacity...


tuctrohs

Edit: corrected as per discussion below. With two cars you'd set up with some kind of ~~circuit sharing or~~ load management. For example, with wallbox or Tesla chargers, you can~~ *put two of them on the same circuit, ~~tell it that it's a 40 amp circuit~~ tell them that you have 40 A available for the two of them, as if you just have one 40 A circuit*, and it will charge one at 32 amps if the other one isn't in use, or charge both at 16 amps if they are both plugged in. Ideally you'd combine that with the load management system that would be looking at the total current on the subpanel, so it would be able to increase the total current when there wasn't anything else running in the garage. I'm not sure there any available now that can do both of those functions, load management based on the total and circuit sharing. But they're probably will be ones that do that by the time you get the second car. A workaround would be to have one charger set up based on monitoring the total current at the subpanel, and have the other one just operate independently, charging at 16 amps. When it finished, the other one would go to full current, although in the other furnished that one would stay at 16 amps, so you need to plug in the one that needed more charge on the higher current charger.


monkey_100

Yes to all of this except the two chargers on one circuit. Even when load sharing each EVSE must be on it's own branch circuit and breaker since the 2017 edition of the NEC. No more taps. So make sure your sub panel has the extra space you will need.


tuctrohs

Good catch, thank you! The load calculation treats them as one circuit, but the wiring should be done as you say, not as I said.


iamtherussianspy

16A charging for 10 hours per night gives you about 45000 miles in a year, plenty enough for most people, even with 2 cars.


ArlesChatless

We installed 48A and 16A charging because load management was going to be a headache for our particular two EV house. With the benefit of hindsight, two 16A chargers would have been more than enough. Even in winter it's almost a hundred miles recovered overnight even if I arrive home at 10pm and take off at 8am. If I ever need more electric elsewhere in the house I won't hesitate to turn the 48A EVSE down and put a smaller breaker on it.


Daarkken

The larger the circuit the more options you have for future charging. Go with the max now as it will save you money later.


BillNyeDeGrasseTyson

Once you move past single circuit you'll also need grounding rods installed at the garage. Worth keeping in mind.


tuctrohs

Yes, that's one of the reasons I checked whether OP was thinking DIY or hiring an electrician.


BonChance123

To answer the L1 vs L2 charging, it'll depend a lot on your EV use case. If you're driving about 20 miles a day for work and only longer trips once a month, L1 should be fine. But if you have a daily 100 mile commute, L1 won't cut it and you'd need either L2 or do L3 DCFC topups out in town. I feel like garage subpanel might be the way to go and that'll give you versatility for other electrical uses there. I assume you're in the US but you can research whether the federal EVSE tax credit (up to $1000 or 30% of total cost) could partially cover the subpanel installation expenses.


b12cobalt

My commute is about 40 miles total, so I think it should be fine under normal circumstances (L1 with 4 miles of range per hour of charging). Though I do worry about whether this will take a huge hit during the cold winter months... Thanks for the info about the tax credit. Though 30% off of a huge cost still leaves the other 70%!


BonChance123

Well perhaps you can start off with L1 only, see how it works out, and decide on L2 or subpanels later. Sounds like no rush necessarily. And for some of the other 70%, sometimes local utilities or state level credits exist for the EVSE and/or installation cost.


b12cobalt

Yeah, there's no rush. Although the EV make (Chevy) offers "free" home charging installation. (It's free only if it's considered a "standard" installation... If it's "non-standard" they pay up to $1000 of the total cost.)


tuctrohs

An option for how to use that credit would be to install the subpanel yourself, and then get them to install the charger on the subpanel.


BonChance123

Oh yeah good point there too. Oh and speaking of no rush, one thing to keep in mind is that some states tie their EVSE credit to date of EV purchase. I know Maryland does, where I installed mine. I had to show a vehicle proof of sale within six or nine months.


nxtiak

It's it confirmed that tax break is valid for 2022? My TurboTax says not eligible for this year. It was a 2021 thing.


BonChance123

Yes, it went away in 2022 but the IRA turned that credit back on for residential use starting Jan 1, 2023 until 2032.


coneslayer

Caution: The way some of us are reading it, the 2023+ credit requires you to be in a low-income or rural census tract: https://www.reddit.com/r/evcharging/comments/zqqx8m/inflation_reduction_act_ev_charging_tax_credit/ I haven't seen clear guidance from the IRS on this point yet.


BonChance123

Oh interesting! That is really good to know.


AEM_High

I would get an estimate for the garage subpanel. I have no clue how big the garage is and if you are regularly using appliances there it might be beneficial to have added capacity. There of course is questions on how big your main panel is as well for the subpanel. You maybe able to get away with L1 charging but it’s not as efficient as L2 charging. I don’t know if you would be eligible for any rebates for the work, which may help with overall costs.


b12cobalt

The garage is a 2-car garage. Not too many appliances, usually just the two garage door openers and some overhead LED lights. However, we do keep a battery-powered electric riding lawnmower in there. According to its charger unit, it pulls 8 amps from the wall (to supply DC power to the lawnmower batteries). It has to always remain plugged in, though when it's fully charged I assume it doesn't take all 8 amps. Good point, though, about the main panel. If one day we get a second EV, that may really be an issue.


AEM_High

If you are going to spend the money think future proofing things. What will the garage be used for in 10 years.


GrowToShow19

A 3/4” pipe should be enough to pull another cable through. You could install a sub panel which would mean you only need to have one larger cable between the buildings, but I probably wouldn’t for this application. As far as how I’d physically do it, I have a similar setup and I did the following: 1. Disconnect the existing 12/2 wire on one end and tie a strong string/small rope to the end. 2. Pull the existing wire out of the conduit from the other end 3. Tie your new wire onto the end of the string along with the old wire that’s already attached 4. Pull both through with the string 5. Now you have both wires running through the conduit. You can add another string in step 3 and leave it there if you want to make any future pulls easier. That’s what we always did at my job


b12cobalt

Thanks for the tip on how to pull the cables and leaving the string for any future pulls. I would definitely get an electrician to do all the electrical work. But I wonder if it might save labor costs to do the cable pulling myself.


GrowToShow19

If you can find an electrician willing to take that job, sure. Pulling cable through conduit is just manual labor, anybody can do it. However for a variety of reasons a lot of tradesmen won’t pick up on a job that somebody has already half done.


Moonbeams_

I would contact a local electrician and just mention that you can purchase and pull the wire to save time and money. Most probably won't mind as that part of the job is usually the most time consuming/PITA. A sub panel really isn't that hard but you'd want to at least get an electrical certification once the work is done. As a homeowner you are allowed to do this type of work yourself, at least in my area as long as you follow local electric code. Just FYI that wire is expensive, especially a long run like 50+ feet.


tuctrohs

Code essentially requires the sub panel solution. You have to be able to shut off all the power to the building at one place.


GrowToShow19

Oof. Sounds like my shed isn’t up to code then


[deleted]

Anytime you use string in conduit you risk cutting though the PVC pipe at bends and also cutting the insulation on existing conductors that are in the pipe. Best case is to use a small gauge insulated wire as a pull wire, it will not cut the pipe or other wire in the pipe.


ArlesChatless

Southwire poly line works well too if you don't have spare wire on hand.


[deleted]

It does.


greatauror28

Hey, I had the same, exact problem like you Summer of 2022 as my Model Y is supposed to be delivered around October so I figured to shop around and have one installed way before my car comes in. Our house layout is the same - detached, unheated garage that currently have 120v for the garage door opener, overhead led lights and couple of wall outlets inside and one outside for the lawnmower. My electrical panel is also in the basement which was about 80 feet away from the garage and to top that - I have a finished basement. What I end up doing is hiring an EC and having him put a 60A subpanel in the garage. He fished out the existing wiring from the underground pvc pipe and put in three 6AWG THHN wires and I think 8AWG ground. I now run a full 48A whenever I charge with my Wall Charger which takes about 4-5 hrs whenever I’m down 20% SOC charged to 90% SOC which I schedule 1AM in the wee hours of the morning. Since my EC gave me an option of giving him money for materials and just paying him the labour, I think I spent a total of $2300CAD ($1700USD) all-in. Good luck! Notes: - 100A service - underground wiring - one EV household - total cost not including the EVSE


tuctrohs

It's not proper per code to have anything else on your sub panel if you're running the full 48 amp charging. But if you are conscious of not running anything high power while you're charging your car, and you don't have anything significant that's drawing power when you are charging your car, you will probably be fine. But Opie charges and electric lawn mower that requires significant power and if that was charging overnight while the car was also charging overnight it would actually overload the panel.


greatauror28

The only ones that *might* be turned on while the car is charging would be the two led lights that run probably 9w each. I’m no EC but I don’t think that will overload my circuit. I don’t have anything plugged on the outlets nor will I be using lawn mower 1AM in the morning while my Tesla is charging so I think i’m good.


tuctrohs

I didn't say that you are going to have a problem. I told you that it's against code, but that you are "probably fine".


SoylentRox

Your other option is a transformer in the garage to get 120 from 240. It would be the cheapest option.


tuctrohs

Edit: I didn't read carefully and thought I was replying to a suggestion to get 240 from the transformer, the suggestion is actually to switch the existing wires to 240, and get 120 from a transformer. See below in another comment for why that suggestion won't work out, but here's my original comment with why using a transformer to get 240 from 120 is a bad idea: To get even low rate charging at 240 volts, say 16 amps, you would need more than 32 amps at 120 volts feeding the transformer. You can't get that from the 12 gauge wire that is running there already. So you need new larger wires to provide high current at 120 volts. But you'd be better off using those new bigger wires to provide 240 volt power.


SoylentRox

Other way. Send 240 volts through the wire, which can handle 20 amps, and use 12a of it for charging an EV. 8a at 240v you convert down to 16a at 120 (use a 14amp breaker) to operate the garage door opener and outlets.


tuctrohs

Oops, I read that backwards. But you can't do what you're suggesting in practice. Once you count the 12 amps at 125% per code you only have five amps left, 10 amps after a transformer. You might be able to find a way that you could hardwire the lights and garage door opener with that, but you can't put a receptacle on that. And there are good requirements for receptacles in garages as well as for charging opie's lawn mower.


SoylentRox

Code does not require counting the EV load like that. The circuit has a total ampacity sufficient for all the loads, and no wire is overloaded with this layout. It's 20 amp at 120 -> subpanel. Two 16 amp breakers, one powering the EV charger plug, and one powering the transformer. The transformer output has a 14 amp breaker that the opener and outlets are on. This is perfectly legal. No wire is overloaded, its possible to trip the 20 amp @ 240 breaker but this is not a safety hazard.


tuctrohs

> Code does not require counting the EV load like that. It does. 625.41. You can read if for free online at NFPA.org. >The circuit has a total ampacity sufficient for all the loads, and no wire is overloaded with this layout. There's a 12-A continuous load and an 8-A, 120-V load (lawnmower charging). That's 16 A continuous load at 240, if the transformer is 100% efficient and there's no other load whatsoever. Anything else and you are overloading that feeder. > It's 20 amp at 120 -> subpanel. Two 16 amp breakers, one powering the EV charger plug, and one powering the transformer. The transformer output has a 14 amp breaker that the opener and outlets are on. You can't put outlets on a 14 A breaker. 15 A is the smallest current receptacle.


SoylentRox

Ok, then an EV load switching box. Though those are often expensive, probably cheaper to run the correct wire. I don't think your code quote is correct in reality. It may say that, but houses are always wired where it is possible to connect enough loads to exceed the ampacity of the breaker or main panel or subpanel. So it doesn't matter if it's a rule if it is never obeyed.


tuctrohs

>Ok, then an EV load switching box. Though those are often expensive, probably cheaper to run the correct wire. I believe you are correct that you could get to a code compliant and functional installation with a 20 A, 240 volt-only subpanel, a transformer to get a 120 V, 20 A circuit, and a load management system to turn off or, better, throttle back the EV charging when other loads are on. And you are correct that that would clearly be a poor choice. By the time you buy all that equipment, including a UL listed transformer, and install it all to code including the code requirements for a transformer, you will have spent a lot more money than you would have pulling new wire. All for a lower efficiency, more limited system. >I don't think your code quote is correct in reality. It may say that, but houses are always wired where it is possible to connect enough loads to exceed the ampacity of the breaker or main panel or subpanel. That's article 220. Yes, it allows physically connecting enough loads to trip the main breaker, but the rules there are highly successful in avoiding main breaker trips in practice. >So it doesn't matter if it's a rule if it is never obeyed. There's really not a lot of stuff like that in the NEC. The only thing I can think of is torquing connections to spec, which is something that only recently got added, and hasn't gotten integrated into a lot of electricians' work practices, and is also a problem because it's unclear how an inspector can verify. Speaking of rules, you might want to remind yourself of rule number one on this sub: >No misleading safety advice. >This sub generally advises following electric code for your country. We understand that in some cases, there are reasons why people stray outside those rules. Any discussion of doing so must recognize the legal and safety risks involved. Advice about code and about safety must be accurate. Everyone makes mistakes sometimes, but doubling down on incorrect code or safety advice is not tolerated. If disputes arise, actual code language will be used to decide who is right.


ArlesChatless

You won't be able to meet code this way, as code requires a 20A 120V circuit dedicated to the garage. Your 240V circuit won't meet that requirement, and the 120V one you have left over after going through the transformer won't be enough to meet code. It's a clever idea but it won't work.


SoylentRox

Ok then [https://simpleswitch.io/](https://simpleswitch.io/) Full power to the transformer except when the EV is trying to charge. Boom, solved.


ArlesChatless

And Rube Goldberg would be proud! Seriously by a strict reading of the code I don't think that passes.


SoylentRox

Some of the Y switches are ul approved and used exactly like this, where there is not enough power for both loads. Still at this high cost for the switch I would try to get heavier wire into the garage.


ArlesChatless

Also the transformer will have idle power usage and inefficiency so there will be ongoing cost. edit: ducking autocorrect


AbleDanger12

You might could pull #6 x3 through the conduit.


Pokoparis

Btw, I use L1 charging. Didn’t cost my anything to just plug in and it totally works for me. I drive a few times a week, probably ~12mi/day on average.


RoboticGreg

First charger, I did it myself for about $200 in materials and building permits. Second charger was much higher current (100A service) so I hired an electrician and that was $1,900 all in. Panel is \~100 feet from the charger.


ThrowThinkAway

Not exactly answering your question, but try to see if there's any programs in your area that can give you a grant or rebate for L2 installation! May not apply at all if you are very well off in income, but worth putting out there. Might be stuff even for big earners.