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Decision Time: 48A or 72A Home charging?

Discussion in 'Model S: Battery & Charging' started by IT Geek, Apr 20, 2017.

  1. IT Geek

    IT Geek Member

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    I've finally moved in to a house where I can get the HPWC installed. The electrician is set to come out this week to give me an estimate on the installation costs for this project. However, one thing could impact the total cost and that is whether or not I want to put in a breaker and wiring capable of delivering 48 amps to the car or a setup capable of putting in 72 amps.

    Personally, based on the normal amount of driving that I do on a daily basis (usually no more than 50 miles, I'm leaning towards just going with the 48 amp solution (and also that's the most my MS can use without upgrading anyway).

    However, I'm a bit torn due to the whole "future proofing" concept that is nagging at me a bit. I do have a 200 amp main service on a house that's relatively new so I doubt there would be any need to upgrade or update the panel or service entry wiring. But the wire that would need to be be run from the panel box would have to be upsized to handle the extra load and that I'm sure adds quite a bit to the overall cost of this project (since it's more 60 feet from the panel box to the garage).

    Any thoughts on this? I don't want to have any regrets down the road that I should have had the bigger wire pulled...but I don't see the need for it right now or in the near future (such as no immediate plans to have a 2nd electric car). Is there anything else I'm missing here that I should consider? Thanks.
     
  2. brkaus

    brkaus Active Member

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    I would personally be willing to pay a few hundred more for 100A home charging, just for future proofing. Agree that it wouldn't help in nearly all cases. But someday may have a second (or third) EV and would be good to have the power capacity nearby.

    Additional costs -
    - Larger wires
    - Increased wire cost
    - harder to pull
    - may need conduit vs. romex
    - Nearby disconnect required if over 60a

    I'd have them quote three options and make an informed decision...
    50A (14-50 outlet), 60A (HPWC), 100A (HPWC)


    In my case, the run is so close to the power panel that going as large as the panel can handle is a no-brainer ($200 more and local power company rebates 1/2 the cost).
     
  3. sdorn

    sdorn Director of Awesome

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    I don't think it costs significantly more to run a larger gauge wire. The significant extra cost comes if you have to upgrade the service to the house. I just had a 100 amp circuit added to my garage, and I had to upgrade from 200 amp to 400 amp service to accommodate it as I was already a little overloaded on the 200 amp service when they did the calculations.

    That cost me just under $10,000 for the service upgrade and the additional circuit and installation of the Tesla wall connector.

    One additional cost when going with a 100 amp circuit is you have to have a local subpanel in the garage where the 100 amp circuit terminates. You can't wire it directly into the wall connector, at least not in the county where I live in Georgia. I don't know how much that added to the cost.
     
  4. BrettS

    BrettS Member

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    For what it's worth, I just went through this exact same thought process and I wound up installing the 100amp breaker and 2 gauge wire to support up to 80amp charging.

    In the end, my thoughts were that while I might not need the full charging speed all the time there could be times where it would be nice to have. Additionally, I figured that future cars will more likely have bigger batteries and the ability to put more power into a bigger battery at once could be useful.

    Finally, it didn't really add a significant cost the to the project, assuming you don't need to do any work with your panel. The bigger breaker might be a little more and the larger wire will be more, but the labor to pull the wire won't really change.

    I'd suggest getting quotes from the electrician to do it both ways and see what the cost difference really is. Keep in mind that if you do need or want to upgrade in the future then it will be significantly more than just doing it now because you'll have to pay for additional labor and replace the breaker and wire that you have already paid for.
     
  5. MasterT

    MasterT Member

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    I was deciding a similar problem a month ago - run wiring for 48 or 72 amp. 48 is more than enough for most of us almost 100% of the time but the price difference for running wires for 72 (100 amp breaker) was only $150 more, so, I decided, why not. I do have 72 Amp charger in my car but only charge at 52. Having an option to charge a bit faster is nice to have but hardly a necessity, IMO.
     
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  6. RichardD

    RichardD Supporting Member

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    I went through this two months ago, and went a different route completely. I wired the UMC route 50Amp breaker. I do have the dual charger option, but given my 60 miles per day driven I charge in 3 hours using the UMC. I did consider the option of the home charger but decided against it. I did 3d print a mount for both the charging unit and the charging cord. For me to go to a 100Amp breaker was close to 4,000 so a 72 was not much more than my 50. I thought I would try this for 6 months and make a decision whether the home charger would be necessary.
     
  7. IT Geek

    IT Geek Member

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    Thanks for the input so far. I should have mentioned that I already purchased and have the HPWC with the 24' cord on it. I bought that as soon as I got the "clear to close" from the mortgage company. :)

    I think you're right, I'll get quotes for both and see what the difference will be. I'm guessing that the 200 amp main that I have will be OK but I don't know that for certain. So that will factor in to things. I think I should also check with my electric company and see if there are any rebates for this work too. Good info.

    I've been dreaming about getting home charging on the car for a while (took delivery in February, but I just moved in six days ago so I've been busy getting everything else going (and charging on 110 @ 3 miles/hr right now) but I'm looking forward to having the full experience of being able to put back all the miles that I drive during the day.
     
  8. brkaus

    brkaus Active Member

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    If you already have the HPWC, 60A is likely the sweet spot. You could also, later on, put in a small panel where that wire terminates, slide the HPWC over a bit, and be able to install a second HPWC set to sharing the load automatically. Future proof.
     
  9. Boatguy

    Boatguy Member

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    For home charging of the MS the 40a charger is fine. I have dual chargers which are useful for destination charging, but not at home.

    The reason to pull larger wire at home is to support two cars. We have two EVs and though we stagger the timing of the charges at night, it's nice to have the ability to charge both if needed.
     
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  10. immolated

    immolated Member

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    One issue I didn't think about was that I ended up having a night shift for a few weeks and could only charge for like 45 mins during the 10pm-6am EV rate, so make sure this isn't in your future, that's the only time I wished I had more than standard charging.
     
  11. msnow

    msnow Active Member

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    Go for the 48. I had the same decision you did when I bought my car and I've never had a need for more. The only use case that would require faster charging would be if you came back from a long trip close to empty and immediately had to leave on another longish trip. That's a very low probability for most people.
     
  12. IT Geek

    IT Geek Member

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    Had a meeting with the electrician this afternoon and he brought up a couple things I did not consider. First I have a finished garage (it's drywalled and painted), I did inform him that I don't mind any holes that get made in the garage since I want to repaint it anyway, but I'd like to run the wiring in the walls. That might pose a problem for the thickness of the wire that would be needed for 100 amps since I have to go through some of the studs to make that happen. i'd have to resort to running exposed conduit if I want 100 amps. Second, the city I'm in might require me to put in a service disconnect if I'm over 60 amps and since the breaker panel is way on the other side of the house and in the basement. That's also more costly to do and I'm not keen on having more stuff mounted to the wall, that's just my personal preference.

    The city that I'm in is the electric company and they do not have any peak/offpeak pricing so there's no savings to be had from setting the car to charge at a specific time of the day. The electric rates are about average though so it's not a big deal.

    My electrician has to contact the city to see what they require for this and I did ask him to quote both options so I guess we'll just see what comes back.

    However, I do want to stay in the walls as it's all finished now...so that alone might get me to stick with the 48 amp option.
     
  13. brkaus

    brkaus Active Member

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    You will be happy with the 60a circuit. My jurisdiction requires a disconnect and my breaker panel is 3 feet away. Panel is outside, HPWC is inside. Could touch both when the garage door is open.

    If it's within a few hundred, I'd go for the 100a anyway and deal with exposed conduit. Personal choice. But 60a will easily meet the needs of a very large % of the population including me.
     
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  14. Lloyd

    Lloyd Well-Known Member

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    I have both, and use the 80 amps about 2 x per year.
     
  15. sdorn

    sdorn Director of Awesome

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    They did not have to run exposed conduit for my 100 amp circuit, but they didn't have to go through any studs as the line came up from the basement. Most places (if not all) require the disconnect for the 100 amp circuit. Mine is mounted right next to my wall connector.
     
  16. David99

    David99 Active Member

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    There is nothing wrong with having the option to charge faster. Although when you are in a crunch, trust me the difference between 48 and 72 Amp is not going to cut it. If you need to charge fast, 72 won't cut it.

    I have driven my Model S 114k miles and never charged faster than 40 amps at home. It's just fine. I do drive a lot, more than 100 miles a day but even if you drive 200 miles a day, a 40 Amp charge is plenty.
     
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  17. bob_p

    bob_p Active Member

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    When we built a new house several years ago, we had them run a 100A circuit for an HPWC to support 80A charging of our S P85 (with dual chargers) and a 14-50 outlet on the other side of the garage for a second EV - both connected to a dedicated panel just for EV charging.

    When our S 100D arrived, we moved the S P85 over to the 14-50 outlet and ordered Tesla's 14-50 connector - and only charge it at 40A.

    The S 100D is connected to the HPWC, but limited to 48A with the standard charger, which should be enough for our charging needs. At least for now, not planning to spend $1900 to upgrade to the 72A charger.

    When future proofing, one consideration is the likely size of future battery packs. Musk stated 100 may be the largest (consumer) battery pack they make - and after driving our S 100D on a short road trip, I agree. The Model 3 will have a smaller battery pack, but also use less energy per mile - and I suspect Tesla will figure out ways to increase efficiency in the S & X in the future (just like they did when moving from rear to dual-motors).
     
  18. Rocky_H

    Rocky_H Active Member

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    I keep seeing a couple of references to the potential need for faster charging in the future because of larger battery packs. That doesn't even make any sense. Just because the batteries may be bigger, that doesn't mean you live farther and farther from work in the future. You drive however many miles you drive, and that's how you back into this calculation. If your longest driving days are still only about 100 miles, it doesn't matter how big the battery is. You can refill that 100 miles in a few hours with the 48A, so it's fine. I don't see much good reason for the higher amp for one car for home overnight charging. If/when you ever get another electric car, you could run another circuit for that.
     
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  19. IT Geek

    IT Geek Member

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    Garage.jpg

    This is my conundrum. The walls are finished. Where I want the HPWC is actually on one of the exterior portions of one of the walls of my attached garage. There's no good way to get the wire from the inside of my house thru the basement unless I go through the part of the garage that is on the inside of the house. As you can see in the picture above, that's about 7 or 8 feet away from where I want the actual charger to be. The interior walls are only 2x4 but the exterior walls are 2x6. it would have been great to do all of this before the house was built...but the original owners apparently didn't think about EVs, go figure. So I'm stuck in the retrofit situation now.

    I do want the charger to be located where I've pictured it so that I can sometimes park in the driveway if needed and still charge the car, or perhaps share my charger with someone else who is parked there.

    Perhaps 48 amp is the way to go for me. Still waiting to see what the quotes will be though.
     
  20. IT Geek

    IT Geek Member

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    Great point.
     

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