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I am looking into installing an electric car charger. I called a few electricians to get a quote. My main panel is full, but there is an existing 50 amp breaker for an electric cooking range which is currently unused since I am using a gas cooking range. All of the electricians I am talking with agree that we can just reuse that breaker.

My town requires a permit and inspection for installing an EVSE. When I mentioned this to one of the electricians who visited to provide a quote, he told me that I would need to replace my existing panel because it has too many tandem breakers (8 currently). He told me that this would be flagged during the inspection and that he would give me a discount if I get it replaced together with the charger installation.

I want to make sure that I really do need to replace the panel and this is not some sort of up-sell. I did some research online and the general idea I get is that as long as the panel allows for tandem breakers in a slot, there should not be a problem with the number of them used. Can anybody here tell me if I really need to replace the panel?

The panel is around 30 years old (the house was built in 92). It is a Square D panel and my service is 200 amps. There is a Cat No. Q020-40M200 mentioned on the box if it is helpful. enter image description here

I also see some listings for 20 spaces - 40 circuits panels online, which look like what I currently have (https://www.lowes.com/pd/Square-D-200-Amp-20-Spaces-40-Circuit-Convertible-Main-Breaker-Panel-Plug-On-Neutral-Load-Center-Value-Pack/50311179).

Edit:

I am not able to take a clear picture of the label on the panel as there are some wires in the way and I am not comfortable moving them. I read about CTL (Circuit Total Limitation) somewhere. The panel mentions CTL, but not all the tandem breakers mention it. enter image description here enter image description here

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    Panel label should mention how many tandems can be in it. Two look alikes can have different labels. If you find that label, should add picture of it to the question.
    – crip659
    Commented Mar 7, 2022 at 19:44
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    Another way to make space is to look for circuits that can be combined. Are any of these 15A or 20A circuits used in practice at closer to 1A? Were any of them for window A/Cs that no longer exist or other defunct machinery? Or for a couple of 500W flood lights that have been replaced with 20W LEDs? Etc .. you know your house, see if any breakers are redundant.
    – jay613
    Commented Mar 7, 2022 at 20:00
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    I think your model number suggests it's a 20 spaces 40 circuits box, which means they can ALL be tandems. So unless your town or state says you can only have 8 tandems, which would be a strangely specific number to impose on all possible panels from all manufacturers, I think you should keep pursuing your Plan A, perhaps with a different electrician. You could also try phoning your town inspector to ask if there is a limit on tandem breakers other than the manufacturer's one.
    – jay613
    Commented Mar 7, 2022 at 23:35
  • Are AFCI and GFCI available in the the tandem breakers? If not, then how many full size standard breakers are there that could be replaced? Commented Mar 8, 2022 at 1:23
  • If you are reluctant to move the wires by hand, you could push them in with a piece of wood and photograph the instructions. Commented Mar 8, 2022 at 3:10

3 Answers 3

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First, you have a SqD QO Loadcenter (Residential Panelboard). It's one of the best panels you can install. These panels have a life cycle of 60 years and many of them last longer than that if they are installed properly. Personally I don't see a need to replace it just yet.

Second, since you have a gas range, I am assuming you at least have Gas Heat and a Gas Dryer. This means that there is a low probability that your panel will be overloaded by adding your charger. Since most of your heavier energy loads are gas.

Third, panel spaces are designed and listed to accept tandem breakers or they are design not accept them, unless there is some sort of local ordinance limiting the number of tandem breakers, I don't know of any reason why you couldn't use as many as the panel is designed to hold.

All that being said:

I don't know of any code reason you could not use the 50A Range Breaker for your charger. However the NEC defines a dwelling as a "facility for one or more persons, including permanent provisions for living, sleeping, cooking and sanitation." Most AHJ consider permanent provisions as an outlet for a range whether it has provisions for gas or not. I would contact your local AHJ and ask them what their thinking is (you might even ask they about the number of tandem spaces that are allowed).

If it turns out you need to add another 50A Breaker, I see that you could actually add two more tandem breakers and that would give you space in your panel to add a 50A 2 Pole breaker. If that can't work I think your second best option would be to add a subpanel and rearrange your circuits to accommodate the new load.

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From the QO2040 model number, that generally reflects 20 spaces 40 circuits implying the panel is listed for use of tandem breakers in all spaces. However Square D "QO" provides only limited choice in double-stuff breakers. They do have 15A and 20A tandem types, however, and I see a number of 15A and 20A circuits still on full-size breakers, which are likely to be possible to consolidate onto tandems.

Very important point here: you must survey the panel for any "Multi-Wire Branch Circuits" (MWBCs) AKA shared-neutral circuits. Any of these must be placed correctly, and with factory listed handle-ties tying their breaker handles. The best hope is that you can use tandem breakers for these, stacking the tandems with one phase of the MWBC on each tandem (on the near side to each other), and using a listed handle-tie for "QO" tandem breakers. Contact a Square D dealer both for the tandem breakers and the requisite handle-ties.

However, if the 50A oven breaker is not serving anything, you can remove that breaker and install the correct breaker for an EVSE. Trying to salvage the 50A breaker is silly; they're under $20.

Note that the charge rate is a "soft setting" on any wall-mount EVSE. So it can be configured to match the circuit you have, or are able to put together.

A few things on your wires.

  • A 3-wire oven circuit cannot be extended, unless the neutral wire is bare; in which case you can convert it to ground and use it for a 240V-only circuit (that does not have neutral).

  • At large sizes, there is nothing wrong with aluminum wire. For instance, a 50A circuit could be run with #6 aluminum if the destination terminals are rated for aluminum wire and 75C thermal rating (which oddly, many EVSE's are not; however most 50A sockets are). So you don't need to bust the bank on copper.

  • A hardwired EV needs a disconnect switch inside the garage. The cheapest, most versatile and generally wonderful way to do that is to install a subpanel in the garage. It's a little more work now, but rather nice later, and it provides the mandatory disconnect switch.

  • If you have any thoughts toward a second EV, you may want a subpanel in the garage anyway so you can exploit the Share2 technology, which allows multiple EVSE's to share one current allocation. (Tesla Wall Connector v2 and v3 already do this). So for instance two 60A EVSE's could share 80A together, giving as much as 60A to any one car). In that case each EVSE gets a 60A circuit but the panel only needs to have 80A feeder.

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  • "if the 50A oven breaker is not serving anything, you can remove that breaker and install the correct breaker for an EVSE" I'm pretty sure you're not allowed to remove the oven circuit. Even if you have gas - the oven circuit needs to be there "in case".
    – J...
    Commented Mar 8, 2022 at 12:49
  • Thank you for the answer. I am planning to get a new breaker and cables for the EVSE. My main point is that the panel already is budgeted for a 50 amp circuit that is unused. So I shouldn't need to replace the panel for load reasons. It does look like there may be other reasons to not use that space.
    – sp1984
    Commented Mar 8, 2022 at 13:21
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    Actually, maybe I take back my comment above - I think this is one of those rare cases where CEC and NEC diverge. CEC requires a 50A range outlet even if gas is used (Rule 26-744(4)) but I don't see anything like that in the NEC. Maybe I'm just missing it, but it seems crazy that you guys would not require a house to have power available for an electric range. Anyway, maybe it is fine to delete or repurpose that 50A but it might be wise to leave it just to preserve the option for an electric range.
    – J...
    Commented Mar 8, 2022 at 18:31
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    No requirement in NEC to provide an unused electric range supply. 2 20 Amp countertop circuits for minor appliances are required, but if you don't have an electric range you don't have to provide for one.
    – Ecnerwal
    Commented Mar 8, 2022 at 21:09
  • @Ecnerwal have to agree with you! just because code requires a cable/circuit to potentially power an electric range in the future, doesn't mean it needs to be hooked up to a breaker now. + Commented Mar 9, 2022 at 23:34
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I went ahead and hired an electrician to just install the EVSE. My intention was to replace the panel only if it was required during the inspection. It probably would have cost more to replace it later, but I considered it a worthwhile risk.

I am happy to report that the EVSE has been installed, and all the inspections have completed successfully without any issues. We didn't even re-use the range circuit breaker. Rather we made space for another 50 amp breaker by installing two more tandem breakers.

So my takeaway is that, as long as one is not exceeding the limits of the panel itself, there should be no problem with the number of tandem breakers that are used. At least in my location.

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