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I am thinking about having an electric vehicle supply equipment (EVSE) installed. In the interest of future proofing for an electric pickup truck coming on the market about a year from now, i would like to have 1 AWG wire installed for 100 amps @ 240 Volts (residential). But my EVSE today is only supposed to draw 32 amps @ 240 Volts, so would it be safe to have wiring installed that is intended for up to 100 amps, and use a 40 amp breaker today incase the current 32 amp evse decides to malfunction, the smaller circuit breaker would trip at 40 amps, and switch out the breaker to 100 amps when the time comes ? Thank You.

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    Since everyone is recommending aluminium without pointing out the risks: don't combine aluminium with copper haphazardly, make sure whatever is doing the cross-over is fine with both. You can't splice them together with ordinary splices, you'll need some marked Cu/Al to combat the increased oxidation or use a metal in between that's fine with both. That is, assuming the rest of your house uses copper. If everything is using aluminium already, there's no problem. Just, copper on aluminium leads to trouble. – Mast Oct 9 at 7:17
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    You have not stated where you are. Although I have completely rewired several homes and installed new main panels over the years with home owner permits, where I live insurance (and government incentives) require that EV chargers specifically be installed by a licensed electrician. Also, in my jurisdiction home owners may only install copper, aluminum must be installed professionally which requires special handling to ensure a safe connection. That you have had to ask this question also suggests that you may want to have this done professionally. Enjoy your (lovely, quiet) EV! – mickeyf Oct 9 at 11:26
  • I am in Minnesota – Nathan R Oct 9 at 12:45
  • I understand your interest in future proofing, but it's very unlikely that batteries, or chargers will ever support 100A 240V. It's equally unlikely that you will want this. You are dealing with some very fundamental laws of physics and although we as humans are getting better at getting close to physical limits we are not likely to get to those levels of efficiency for household purposes ever. You're far more likely to want a 3 phase power source, which are very expensive to get in homes. – Sam Oct 9 at 14:14
  • I am thinking of having an electrician run a dedicated 240V line to the future EVSE that is designed to run on 100 amps @ 240V, i was previously thinking an all aluminum run from the panel to the EVSE, would it pose an issue to have copper and aluminum wire coming out of the same (only) panel ? (copper to all 120V outlets, light fixtures, appliances such as gas range and fridge currently) Also, the EVSE instalation instructions say to use copper connections only on anything touching the evse. – Nathan R Oct 9 at 14:59
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Sure, you can always upsize the wire.

However, a dramatic upsize introduces two complications.

  • the much-larger wire will not fit on the device. It will need to be pigtailed to a suitably sized wire, such as a 6 AWG.

When dealing with #1 wire, it's not as simple as using a giant orange wire-nut the size of a salt shaker. You have to use a connector such as a Polaris, which is an insulated lug terminal. You could also use uninsulated lug terminals or split bolts, if you don't mind lashing it under unbelievable amounts of electrical tape. You do need to insulate neutrals.

  • You are probably dealing with aluminum wire (I hope)

Generally all terminations sized for #1 wire are aluminum friendly; why wouldn't they, since aluminum is normal and expected at these sizes. You just have to take care to use terminations rated for aluminum; a Polaris is fine, however I would not use a split bolt unless the smaller wire is also aluminum. Aluminum is fine to use at these sizes.

But yes, definitely lay the heavier wire. The only case where I wouldn't is if the wire was in conduit, and the run is very short. In that case, the pigtail adapters for the larger wire might be more expensive than just doing the whole run in the smaller wire. It could be changed for the larger wire later.

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You can run larger cable and use a smaller breaker but not the other way around. If your planning on 1 AWG for 100 Amps then you're talking about aluminum cable. You'll have to pigtail at both ends to a 8 AWG because the 1 AWG won't fit in the 40 Amp breaker or receptacle. That future 100 Amp load could be a strain on your panel so check into that along with your other planning.

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Yes, having larger wire is always fine. Depending what size wire the terminals on the 40 amp breaker are listed for you might need a pigtail of wire that fits that breaker connected to your 1 AWG, but that's a common problem with a straightforward solution. You should consider using aluminum wire for a run this big, if you are presently looking at copper.

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