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I'm following up regarding adding 50 amps to provide service to an EV charger. Crazily, I have two 200 amp service panels and both are full. As suggested in responses to an earlier post, I am attaching pictures of the panel and my recent work to map the breakers on the panel (what was labeled by the previous owner was vague/inaccurate).

Please ask any questions as I'm trying to figure a lot of this stuff out myself. For what it is worth, a lot of these things are rarely or almost never used but since they could be used in the future I don't want to terminate them.

Note, I intend to hire an electrician to do this work, with me possibly (depending on cost) pulling the 6/2 cable since I have a large conduit from the panel to an unfinished utility room that goes directly into my garage (about a 75 to 100-foot run). I just want to get a sense of what I can expect, what I should ask for, and whether I'll need yet another panel!

Thanks in advance.

EDIT TO ANSWER QUESTIONS: House is very large and has tons of gadgets added by the original owner. There is an addition that has an Endless Pool in it. This is rarely used, maybe a handful of times per year. This has the pool, pool pumps, swim resistance motor, its own AC unit, a huge dehumidifier (not needed with sealed cover and little use). Otherwise, we have gas heat for the basement/lower level and electric/heat pump on the top level. On the steam shower, again this is just used a handful of times each year. On the cooktop, it is a gas cooktop that has a blower that raises and lowers. Not sure why, but it won't work without both breakers on.

Labeled Breakers

Panel 1Panel 2

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  • Please take the tour and be sure to follow up with your earlier post.
    – isherwood
    Mar 8, 2022 at 13:59
  • You have 4 A/C circuits ... presumably that's two compressors and two blowers? You have 3 furnaces in addition to "pool heat". Is the third furnace, "Pool room furnace", is that to heat an outbuilding? You have two circuits for "cooktop blower" ... what's that? What about the actual cooktop .. where is that? If that's gas why is everything else electric?
    – jay613
    Mar 8, 2022 at 15:09
  • @jay613 There is an addition that has an Endless Pool in it. This is rarely used, maybe a handful of times per year. This has the pool, pool pumps, swim resistance motor, its own AC unit, a huge dehumidifier (not needed with sealed cover and little use). Otherwise, we have gas heat for the basement/lower level and electric/heat pump on the top level. On the steam shower, again this is just used a handful of times each year. On the cooktop, it is a gas cooktop that has a blower that raises and lowers. Not sure why, but it won't work without both breakers on.
    – Farcical
    Mar 8, 2022 at 15:29
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    It is hard for me to imagine any house requiring more than two 200 A panels. Some of the lighting circuits are surely serving small loads and so could be combined by putting two wires in one breaker. Some combination of that and using the 1/2 inch wide breakers would likely free enough space for a 2-pole 60 A breaker. The thin std 2-pole breakers come at least as large as 50 A. Is the EV going to be through a plug or hard wired? Does a NEMA 14-50R in a garage require a GFCI breaker? What about hard wired? Mar 9, 2022 at 1:01
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    Can you post the square footage of your house, as well as photos of the nameplates of all HVAC equipment, the nameplate kW ratings of your oven and pool heater, and the HP ratings of the pool pump, well pump, sump pump, and endless pool motors, please? Mar 9, 2022 at 4:59

2 Answers 2

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Reading between the above lines and doing a lot of guessing, you probably have a large house so should factor at least 100A for lighting and general power (it's a sq ft calc you can do). Your heat and A/C seem to each require about 90A (guessing their actual load), your pool/hot tub complex seems to need about 150A. And all your special loads (steam shower, dryer, washers, sump pump, etc etc etc) also guessing their actual loads could potentially together draw another 190A.

IMO you are WAY oversubscribed already, and you cannot add an EV charger without either bringing in another service drop or installing some kind of load sharing device to share power between the EV and certain existing fixtures, eg "pool room furnace", "steam shower", etc.

I don't think your "full" panels are the main issue, you could move some stuff into a sub panel eg a bunch of lighting circuits. I think the issue is you can't add another 12kW fixed load to your service, you'll be blowing your 200A breakers.

I infer that natural gas is not available at your location, right? You might find that converting your entire pool complex to propane would be more economical than upgrading your electric service even further. Worth looking into.

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  • Responding to your comment to the Question, you mention some things are "rarely used". I don't know how to factor that into load calcs for code purposes, and I did not factor it in this answer. I assume that, even if on rare occasions, ALL your pool equipment plus all of either your heaters or A/Cs, plus a significant portion of your special loads (dryer, shower, sump, etc) might conspire to be on at the same time. If there is some approach that allows you to assume otherwise and add another 12kW fixed load to this scenario, I hope someone else knows about it.
    – jay613
    Mar 8, 2022 at 15:41
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    @jay613 OP has gas furnace in basement and gas cooktop. This is not an all electric house. Mar 8, 2022 at 17:29
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    @JimStewart yup, so if OP determines that a service upgrade to 600A is required, (s)he will hopefully consider the alternative of converting various things to gas where possible. I think I've answered the question, i.e. "no" a 50A EV can't just be added to this situation as-is. How to move forward is a whole new question that I think would hinge very much on costs that I have no ability to even WAG.
    – jay613
    Mar 8, 2022 at 17:49
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    Note, I did not simply add everything up but I did resort to much guessing to imagine what a maximum load would be, and that it would be over 320A. I imagined all the pool equipment running because you have some guests over and enjoying it all to the max. Of course the oven is on, to feed them, the dryer for all their towels, the A/Cs are both running because it's summer. Etc. I used guesstimates of what similar equipment USES, not your breaker ratings. YOU can look up ACTUAL max consumption from all your actual large equipment and design your own peak scenario to add up.
    – jay613
    Mar 9, 2022 at 17:58
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    One could also consider disconnecting things entirely if they really aren't being used. Maintaining even a small and mostly-unused pool takes a significant amount of attention, chemistry, and electricity; it's a luxury that I envy but it may be a luxury you can mothball until you intend to use it more seriously.
    – keshlam
    Dec 4, 2022 at 3:27
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As already noted, a load calculation is key here. But really 3 load calculations:

  • Total Service - 320A
  • Panel 1 - 200A
  • Panel 2 - 200A

With a typical 200A or smaller service, there is an alternative method. Not sanctioned by code but often very practical: Check your utility usage reports. Many utilities provide free downloads showing 15-minute, 30-minute or hourly usage for a year or more. For example, my hourly usage for November 2020 - November 2021 shows a maximum of 9.98 kWh. At 240V (of course, not all loads are balanced, but the large ones are) that's 42A, so that tells me the near-peak (true peak would need peak demand kW in each interval rather than kWh usage) value. That's effectively your maximum load for the year, whether the load calculation comes up lower (you run more stuff at a time than the average homeowner) or higher (you run less stuff at a time). It is also helpful for figuring out generator capacity - 98% of my intervals are under 6 kWh, so I know a 7,500W generator is a reasonable match as long as I don't hit the absolute peak, which can easily be done by not putting the oven and clothes dryer on the generator.

The problem is that with a house/service this large, it is unlikely that your real peak usage is below 140A. If your peak usage is 200A then adding 50A to your service is OK, because it will only max. out at 250A. (Leaving aside the issue of whether a future owner might use the pool or other equipment more and run into trouble.) But since the utility can't tell you the split between the panels, you won't know which panel can handle an extra 50A. The real usage by be 160A on one and 40A on the other. Or flipped. Or even worse, balanced to one side in the winter (heat) and to the other side in the summer (air conditioning, pool), etc. Which is why load calculation is a very useful tool.

The other issue is whether you need 50A of charging capacity. Since you indicated you will do night-time charging, that typically means 8 - 10 hours of uninterrupted charging. 30A (possibly even 20A) of 240V charging is more than enough for most people using their cars for typical commuting and errands. But given your current (pun intended) situation, even adding 20A may be problematic.

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