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Talk me into 100A wiring vs 50A wiring

Discussion in 'Charging Standards and Infrastructure' started by jimmyz80, Mar 15, 2017.

  1. jimmyz80

    jimmyz80 Member

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    So here's my dilemma... I have a Model S showing up in a month or so which will only have the 48A charger, and I have a Model 3 hopefully showing up sometime later this year that I'm assuming will also be a ~48A car. These charging rates will meet my needs easily, since I rarely drive more than about 100 miles in a day. I've survived just fine with a LEAF and a 20A EVSE.

    I have two wall connectors ready to install, and the nerd in me wants to just max them out with 100A wiring to future proof things. This will of course be more expensive and more complex to install. I'd need to run conduit for the wiring since NM isn't an option, and I'd have to architect it all around Power Sharing since I can't run two individual 100A circuits from my total 200A household service.

    For 50A wiring I could just run some 6/2-NM through my crawl space and be done with it. I'd get 40A to the car vs. the max of 48A, but I'm sure I could live with that just fine.

    Is there any reason at all to bite the bullet and install for 100A? Barring any future cars being massively LESS efficient, I just don't see a reason for me personally.

    Is my logic sound? :)
     
  2. azred

    azred Member

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    I'm in exactly the same situation except I already have an S and am not at all concerned about the arrival of my Model 3 needing the expensive upgrade. It's not even on the bottom of my wish list. I have the 24 foot cord and will share the 48A.
     
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  3. Deans

    Deans Member

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    I'm not an electrician, but I'd just do 50A and worry about the future in the future. By the time it matters, if ever, there might be high speed charging stations everywhere anyway. KISS.
     
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  4. rypalmer

    rypalmer Member

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    Will your cars be charging outdoors? If so I'd suggest a minimum of 30 amps per vehicle on a shared circuit, since you probably do see some cold temperatures. I did the math on this recently when we had to bury a service to the driveway and wanted to be reasonably future proof for 2 EVs in the winter.

    Either way.. just install one for now and sell the other wall connector. There could be something better out by then, and you'll just waste the warranty period on the unused one in the mean time.
     
  5. jimmyz80

    jimmyz80 Member

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    Well I just bought both of them and we should be pretty early on the Model 3 list, so I'm most likely going to wire them both up.

    Both cars will be charging inside and in the case of going 50A, I'd be running 50A to each wall connector without using Power Sharing. I do have a Clipper Creek 20A J1772 outside already in case I need to charge in the driveway or charge a guest's non-Tesla EV.
     
  6. JohnSnowNW

    JohnSnowNW Active Member

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    We installed 100A at our current house so we could reasonably charge 2 BEVs simultaneously.
     
  7. jimmyz80

    jimmyz80 Member

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    Which would be the same as me running 50A to each of my Wall Connectors. :)
     
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  8. JohnSnowNW

    JohnSnowNW Active Member

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    True. We were forced to install a sub panel in the garage, so it just made sense to run a 100A line to it.
     
  9. MX1028

    MX1028 Member

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    The Tesla connector power options chart...(Home charging installation)

    When waiting for my Tesla I went through this chart. My conclusion was max 60 amps because everything else will require upgrade to the High Amperage Charger.
    Also the combination of 60amps and Wall Charger pulls full 48A to get the max 34miles/hour charge. Even if 70 - 100 amps circuit breaker is installed the Wall Charger is smart enough to negotiate it down. So no real value in adding higher circuit breakers.

    upload_2017-3-15_15-47-19.png
     
  10. RayW

    RayW Member

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    I believe you can also install two connected Tesla wall chargers and they will manage the charging so not to blow your circuit breaker.
     
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  11. jimmyz80

    jimmyz80 Member

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    Correct, that's the Power Sharing feature. If I went with 100A wiring I'd need to use that, but for 50A I most likely wouldn't, so each wall connector would have a full 50A available.
     
  12. bak_phy

    bak_phy Member

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    If you are OK with 40 amps per car now rather than 48amps just do that. If you have a 200 amp main breaker like most of us you probably would not be able to charge two cars at 100 amps simultaneously anyways.
    Given how much people tend to move you may well just be upgrading from some other guy who will pay you exactly $0 for the effort.
     
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  13. bak_phy

    bak_phy Member

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    I realize that I'm obviously not helping you achieve what you asked for in the title. Sorry.
     
  14. JHWJR

    JHWJR Member

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    I tossed it around a bit too. I have a Model X on the way. I intended to get dual charger, but the sales guy talked me out of that, explaining that, in his view, few people will ever use it meaningfully. So, I'm at 48 amps in the car and saved that cash.

    But I was looking for a reason to justify 100 amp service

    The modest difference in price was one way: I'm already paying for the electrician to run the cable and it's not much more to run 2 AWG cable than 6 AWG. But the 100 amp service does require, in my neck of the woods, a "Disconnect Box." Not sure how much I paid for that, but I'm sure it was a bigger part of the bill than expected or want to know because that's not a small device it turns out. (It was not broken down in the estimate or the invoice.)

    So, I might someday upgrade to 72 amps. Yeah. That's it. I might do that. Then I'll be glad I put in a service that can deliver 80 amps all night long (i.e., 100 amp service.)

    And I have a brother-in-law who lives 150 miles away. HE will be glad I put in the 100 amp service when he visits because I'm pretty sure he got the dual charger option. (Turns out he didn't.)

    And I might want to get a 2nd Tesla and the 100 amp service will let me charge both cars at nearly full power, though that would require a second wall connector or perhaps adding a 50A outlet (which I did not do) and/or getting another wall connector. But that's awfully iffy, and the truth is I could pretty much charge 2 cars on a 50 amp service if I have all night, which is what I'm talking about anyway.

    Or if I happen to find a destination charger that can deliver big amps, which almost none of them do, it turns out.

    So, with all these reasons failing to justify 100 amps, I did it anyway. Just for the geekiness, and it SOUNDS good with my 100D. :-/
     
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  15. jimmyz80

    jimmyz80 Member

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    Pretty much my thoughts exactly. For 100A I'd have to use the Power Sharing feature, meaning ultimately with two cars charging I'd still just be at 40A to each car (same situation as simply running 50A to each wall connector separately). The only upside of using 100A and Power Sharing is that a single car could pull a full 80A if needed. But I don't own such a car and most likely won't unless the base-model charging transitions from 48A to 80A at some point in the future.
     
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  16. AB4EJ

    AB4EJ Member

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    Two circuits, each 50 A (as you have been discussing) seems quite adequate to me. Most thinking on higher power charging at home (i.e., 72 A, 100 A etc on a single vehicle) is that this is rarely needed. Coming roll-outs of public DC fast-charging may completely eliminate the need for this power level (100 A per vehicle) at home.
     
  17. vdiv

    vdiv Chief Grump

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    With a 100A circuit you can always reduce the current while charging, with a 50A one, well you're stuck with 50A. The cost difference is incremental, but the regrets afterwards for not getting 100A are perpetual :)
    Consider other factors such as other loads in your house, ventilation in the garage, slightly better efficiency if the current is not close to the wiring ampacity or the onboard charger(s) limits.
    I would not compromise if I didn't have to and would install 100A.
     
  18. timx

    timx Member

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    If your house and electrical usage is "typical", I would be skeptical if 200A service would be sufficient for much more than charging with a single 50A connection. Consider continuous loads simultaneously: A/C: 40A + AHU 20A + Oven 30A + Stove 30A + Dryer 30A + Washer 20A = 170A -- 80% of that (rated usage compared to breaker) is 136A; lighting and plugs then maybe 20A combined, and there's not much left.

    For my installation, I had to upgrade utility service to 400A (two separate 200A meters) in order to run a 100A circuit for HPWC.
     
  19. jimmyz80

    jimmyz80 Member

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    I guess I'll have to find an electrician who's willing to do the full load calculation. For the three EVSE installations I've had done in the past, none of them cared about anything beyond whether there was space for the breaker, lol.

    We do have two totally separate HVAC zones to run, which cuts into the capacity quite a lot. If I have to, I'm sure we could survive even with 50A split between the two wall connectors using the power sharing feature. Not ideal but we'd survive, since I don't have a commute and my wife doesn't drive a whole lot.
     
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  20. animorph

    animorph Member

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    I have 200A service, about 4000 sqft house with three heat pumps but gas water heater, cook top, and dryer. We were able to replace the unused 50A cook top circuit with a new 100A breaker for a HPWC. The load calculation came out at 199.xA total, so we were pushing it. The inspector didn't even look at the load calc, but did check the HPWC manual to see that it could work with the 100A breaker. That's for the Model X that's in production now. I did get the 72A charger, but that's more for travel speed than local use.

    When the Model 3 comes I'll add a second HPWC sharing the 100A circuit.

    I doubt we'll ever really need the faster charging. I would have been fine dialing back the circuit breaker size if the load calc had required it. But the cost difference between 50A and 100A seemed minimal, and you never know when 100A may come in handy.
     
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