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I’m awaiting an EV I ordered, and in order to prepare for it, need to install a 240V outlet in my garage.

The circuit would be for a 'Ford Connected Charge Station':

  • 60A breaker (240V, 2 pole, 60 Hz) with a 4-wire configuration

I currently have 100A service—however we have a gas stove, gas water heater, gas dryer, and gas range. Considering the EV would charge overnight, other than refrigerator, lights, alarm clocks, phone charging, etc., the total potential loads during that time would be:

  • EV charger 60A (nominal current 48A)
  • Central A/C 240V/30A
  • 5,000 BTU Room A/C 120V (7A on 15A circuit)
  • Dishwasher 120V/20A

Currently my panel includes a 240V/20A circuit (outlet pictured) that I'm removing, as it's no longer used. Based on these factors, should I add a sub panel in order to add this circuit, or can the 60A safely replace the 20A?

Thanks in advance!

My panel, with inset of unused 240V/20A circuit

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  • How many square feet is your house, and what are the nameplate amp (minimum circut ampacity/MCA) ratings for your A/Cs and dishwasher? Also, how many of those 20A single pole breakers feed kitchen countertop receptacles?
    – ThreePhaseEel
    May 8, 2021 at 3:16
  • When you replace that breaker, because you're full up on breaker slots, you might wish to check if you can get a 60 2 pole plus 2 15 1 pole breaker to fill that slot. Sometimes price is not much higher and it would free up 2 full slots for use at a later date. If you put in a subpanel for your 60A load, you'd still need a 60A breaker in the main panel to feed the subpanel. To me it seems unlikely your 100A will trip based on the lack of other large loads, but if you install the car charger on the 100A panel and it trips the breaker, you can then upgrade your service to 200A.
    – K H
    May 8, 2021 at 3:30
  • Anyway, electrical codes are quite regional, so you should include where you live. You can also contact your inspection department ahead of time to run it by them and if they want you to proactively upgrade your service, they'll be happy to tell you.
    – K H
    May 8, 2021 at 3:32
  • Also when you're sizing your wire, based on the length of the wire and it's resistance per length, you can calculate how much power is being wasted in volt drop. Where I live a 60A 240V load costs 0.86 maple dollars per hour. At a pessimistic 6 hours per night, 365 days a year, that's $1892.16 per year in electricity. If you can bring your volt drop (power wasted) down by a few percent, you save ~19$ per year per percent in electricity cost. Volt drop is not always high enough to worry about, but larger wire is not always proportionally more expensive, so savings may be had.
    – K H
    May 8, 2021 at 3:39
  • The house is 2000 square feet. The MCA rating for the central A/C is 18.8. The room A/C is 450W/4.1A, and the dishwasher is 15A, but on a shared 20A circuit with the garbage disposal. There are 4 kitchen countertop outlets, including a GFCI. I’m in MA, where the code is based on NFPA 70, 2020 edition. Fortunately, the wire run will be short, no more than 10-12’ max, as the panel is in a corner of the basement that abuts the garage wall. Would 6-gauge copper suffice to minimize volt drop?
    – oadesign
    May 8, 2021 at 13:28

1 Answer 1

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You're putting a 60A breaker in a 100A panel. That's fine.

The total of the breakers is more than the panel, because we assume every circuit will not be drawing full power at the same time. That's fine. But if you use everything at once it may trip your 100A service. Unlikely, but possible. When do you plan to upgrade to 200A?

Obviously you need to run 60A wire to your charger, and keeping that run as short as possible will save $$ in wire and voltage drop. Comment above about thicker wire is absolutely correct. UNLESS code in your area requires a sub panel (I would have to look up the code) you don't need it for the electrons.

Free access to NEC at NFPA

You will NOT, of course, replace the 20/20 breaker with a 60/60 and connect to the old 12ga wire. But you knew that. That answer missed the point.

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  • Code won’t require a sub there is no difference as ether method would use the double pole, EV chargers are considered a continuous load although they rarely draw a full load for 3 hours. With all gas appliances and the largest load being the AC your service is probably fine I agree. But I would be prepared to upgrade if there is a problem
    – Ed Beal
    May 9, 2021 at 16:44

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