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Community and Q&A

Largest Possible Residential Electrical Panel

Bernard Lam | Posted in General Questions on

What’s the largest electric service you can “normally” get for residential? Here in CO xcel gives me the option of 400A. My electrician says that usually means a 320A meter base with 2x200A disconnects, for a 320A continious, 400A max service. Has anyone had any bigger?

I’m realising that an all electric (large) house of the future needs a really really big panel. Imagine 2 EVs, along with the usual high load HVAC, WH, dryer, stove/oven etc. And then for a bit of luxury maybe a hot tub, steam shower, maybe even an electric sauna. That’s a lot of amps! Not much capacity left if you ever want to finish a basement or add an ADU etc.

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Replies

  1. Trevor Lambert | | #1

    Not many people are going to have a steam shower, sauna and hot tub, hopefully. Seems awfully extravagant. Even with those, I'd be surprised if you needed over 320A.

    As a starting reference, a modest but efficient house can easily run on 125A. That includes everything except your EVs and full service, professional spa for 10 people. Just charge your vehicles late at night when your spa is closed. An ADU isn't going to add much, and finishing a basement will be next to nothing.

    Charge your vehicles at night, when your full service spa is not in operation.

    You can probably find a load calculator online that you can fill in with your details.

  2. mgensler | | #2

    We have 2 EVs, a hot tub, pool, 3 heat pumps, an all electric kitchen, two electric washers/dryers on a 200 amp service. The largest loads have been around 22,000 watts and only for a brief time. This is around half the capacity, I believe. The biggest issue is the quantity of circuits. We have two subpanels and the main panel has a few tandem breakers as well.

    1. Charlie Sullivan | | #16

      And we have an all electric house in NH with one EV on a plenty fast 32 A charger on a 100 A panel and the highest peak load we've had is 60 A.

  3. Joe Norm | | #3

    The idea is the loads never run simultaneously. a 400Amp service should be plenty for any all-electric residence with all the bells and whistles. 200A is overkill for most houses but with EV's becoming more common they will look more and more necessary.

    The only times I've seen larger than 400amp services was for "compound" type properties where there are multiple houses, garages, shops, etc. Then you might have a 600 or 800 amp service.

  4. Expert Member
    Zephyr7 | | #4

    The largest standard residential electrical panel is a 200A panel. You want to make sure you get a true 40 space panel too, not one of the "20 space, 40 circuit" panels that requires the use of tandem breakers and is a much tighter fit for wiring.

    The "400A" services are really 320A continous, and typically feed two standard 200A panels with seperate disconnects. You can put additional 200A panels if you want, as long as each has a disconnect (breaker), up to a maximum of 6 -- the code allows a maximum of 6 "main" disconnects per structure.

    If you need a lot of space, what I would do instead of looking for a massive panel (which would push you into commercial panels, which are semicustom and a lot more expensive), I would put in a trough, a sort of long and skinny junction box, then tap several 200A panels off of it. If you need a LOT of panels, you can put one main breaker feeding several "main lug" panels which have lugs intead of main breakers. In this way, you can feed as many panels as you want off of a single main breaker, as long as you keep the loads within the capacity of the system.

    If you want to have one "main" panel that feeds a bunch of sub panels, and you want to have high capacity feeds (typicall over 100A) to those panels, then you need a commercial panel with breakers of what are known as a "larger frame size", which will look like "main" breakers. These panels are common commercially, but rare in residential projects. With a panel like this, you'd have a 400A main, then subfeed breakers to feed all the other panels. This type of system can scale very large, and is a small version of the systems I design for large commercial electrical systems at work.

    Note that even a good size home with a lot of electrical gizmos is typically going to be fine with 200A service. You won't be running everything at once, and even 200A is quite a lot. Remember that you don't add up the amp numbers from all the branch circuit breakers to figure out the size service you need, you add up the actual loads you have. That means a 20A circuit feeding a 1500 watt device is only 12.5A of actual load. You don't usually work things out that way though, load calculations are done with KVA numbers, so you add up all of those numbers, then divide by the system voltage and size your breakers and feeders off of that, taking into account applicable codes (80% rule, demand factors sometimes, etc.). I wouldn't recommend sizing a large electric service as a DIY project. These load calcs are part of the permit submittals we have to provide along with building plans for commercial projects.

    Bill

    1. Bernard Lam | | #6

      Thank you bill for the insights. The service that i should be getting is attached. I know very little about electrical designs, even as an engineer myself. And my electrician has not been the best at communication. And you guys have already given me much better explainations on how all this works.

      I think he said the meter/disconnects in this photo and PDF and then a sub panel in the mech room and another in the garage. Initially he wanted a meter/panel combo outside, and then the sub panels inside, but apparently with the new code requirements, the new combo meter redesign won't be available for many months.

      And from what you have told me above, my electrician will do the load calc and everything will be fine. We'll just want to make sure we will have enough space (I.e. not capacity that I was originally worried about) in the panels for future expansion. It's just the thought of multiple EVs, the spa, and then the future ADU, and I want a welding/wood shop in the garage, etc. Seems like a lot of big loads, and I did add up all the amps like you told me not to, and wondered if I'd have enough.

      In response to others and a bit more background:

      It's a decent size house at 3700sqft which includes a 500sqft garage, so not that large by american standards. 5bed 3bath. There's about 500sqft more of basement that can be finished into an ADU in the future, so potentially an additional set of laundry, cooktop/range etc.

      Indeed with a lot of bells and whistles. 2 EVs, welding/wood shop tools, lots of AV toys (multiple 2000w subs), full spa as mentioned. I wasn't shying away from the whole sauna steam shower thing from an energy standpoint because i feel that heat isn't wasted - itll just heat the home, and obviously these amenities only get used occasionally. With the hot tub being the exception. But, here's the big but. Tesla has approved to give me a 25kw solar roof. It's a 2700sqft south facing shed roof that I specifically designed for max PV production (within reason, I.e. it's shallower than optimum) I designed the building with the architect with the solar roof in mind. (See pic). And from the little Beopt energy modelling I have done I'm pretty sure I'll be net zero no matter what, unless i start mining crypto.....(this is a joke)

      1. Expert Member
        Malcolm Taylor | | #9

        Bernard,

        I remember you posting the plans for this house. Good to see it's so far along.

        1. Bernard Lam | | #10

          Thank you for the kind words. It's been a grueling few years and I feel im going to be working on this for the rest of my life. The one good news for a while is this tesla roof, until very recently I don't even know if I will be able to get it (utility approval because the size, and then massive price increase). So I was very conservative in terms of energy usage, but now, if I can get this 25kw system, then I feel better about a few extra luxury features, which is what made me wonder at such a late stage if my panels/service will limit me for these extra amenities.

          1. Expert Member
            Malcolm Taylor | | #11

            Bernard,

            One day you will find yourself sitting in the sunny living room and the memory of all that work will transform itself into an intense sense of accomplishment in what you have achieved. There are few things more satisfying than building your own house.

      2. Expert Member
        Zephyr7 | | #12

        I don't like combo meter/panel setups. I like the meter to be seperate, always.

        What your first pic shows is the meter and two disconnects, I can't tell if they're fused or breakered since they're both closed. I prefer fused mains as they are more reliable, especially outdoors. I prefer to keep all switchgear (anything that switches, so breakers, fusible switches, etc.), indoors since it will last longer. As long as you have the correct 3R ranted enclosures though, code allows stuff to be outdoors too.

        Meter bases are usually specified by the utility. I like to say they specify these in what I call "thou shalt" form. What this means is the "spec" is essentially written something like "though shalt install Milbank model 123abc on thy house, else we shall not connect thee to service". Once the utility has spoken, that's it -- you can't get them to change their ways, so you just have to use what they spec. Don't even try arguing with them.

        The panels and everything else can be pretty much whatever you want. I usually use Siemens stuff, because they make everything from wee small up to vast and huge, the quality is good, and they don't gouge as much for future add-ons as some do. MAKE SURE you buy ALL your breakers WITH a panel to get good pricing. Think you might need some extra breakers in the future? Buy'em now, when you buy the panel. The discounts for breakers bought WITH a panel are pretty substantial when buying through a supply house.

        You'll probably have the usual two 200A panels, one fed from each of the two disconnects. Akos mentions the limitations on solar, so keep that in mind. I don't do much with solar, so I'm not particular up to speed on those particular codes. You may find it easier to tap another disconnect off of the meter, or one of the two disconnects, instead of feeding the solar system through one of the panels.

        I would recommend you partition your loads with one of those panels running "regular" house loads, and the other running your EVs, shop stuff, other things like that. The reason is this keeps some of the large loads off of your house panel so that if you do any work or have a fault, you have one panel of "this has to work, it's in the house", and the other panel is "this can shut off for a while, I don't need to run my saw right now". Make sure to prioritize load balancing though, segmentation of loads should be secondary to that.

        I was just looking at some Crown amps for a subwoofer myself. Waaay back I worked in a recording studio and did sound reinforcement work (fancy way to say I helped design sound systems in theaters and clubs). If you look closely, those amps don't draw as much as they put out, because their rated output power is for peaks -- dynamic power -- and not usually RMS power. Behringer makes some amps that have a combined output of 3,000+ watts, put still plug into a regular circuit (15A circuits can handle about 1,800 watts max, 20A circuits about 2,400 watts, on 120 volts). Your subwoofer amplifiers will likely need a few extra circuits, but they will run MUCH lower average power levels than you might think from their output rating.

        If you have an electrical one line drawing for your build I can eyeball it for you, maybe offer some suggestions.

        Bill

        1. Bernard Lam | | #14

          Funny that you mention crown amps for subs - it's exactly what ive been intending. Currently I have a XLS1500 that I used to push a couple 15"s from partsexpress. Subs and amps are one of those things in life that you don't think you need more until you do. Never thought I'd want more than 1500rms but before you know it the amp was clipping, so this time around I'm going all in, I want lots of headroom at clubbing levels. I'm planning on 2 "bass tower/arrays", 6x 12" or 15" per side. Im one of those people that prefer to have my subs showing and making a statement rather than stealth installs - which I have considered, I.e. having them built into the stud bays. I have a 2x10 double height LVL wall that could take these subs, but every time I think about it, I feel that I don't want to risk the subs cracking the drywall mud from its vibrations. (I attached some pics of this balloon framed LVL wall, which probably should have been done in steel, but that's a different discussion).

          Regardless, i found some XLC2800 for really cheap on eBay - the reason they are so cheap is because they are the 220v "euro" version. But then I did some research and everyone I talked to told me that it should work fine at 240v in the US. Whether it's single phase (euro) or dual phase (us), or 220v or 240v should not make a difference. I was advised to install a 240/20A circuit/outlet with #12 wire, and a 6-15p plug for the amp. Since im running dedicated circuits anyway, 120 or 240 should be similar cost. And the 240/20a outlet can have 2 of those amps plugged into it - each bridged to provide 2400Wrms pushing 6-8 drivers. Very very overkill but in use it might be only drawing 10% of that power. Maybe I'd just do one xlc2800 if im using 12"s and 2 amps if im using 15s.

          You might be interested in this amp too. Just leave a couple for me. Hint: make a $250 offer.

          https://www.ebay.com/itm/CROWN-AUDIO-800W-POWER-AMPLIFIER-XLC2800-brand-new-in-sealed-box-220V-EUROPE-/203250353737?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=711-127632-2357-0

      3. Charlie Sullivan | | #17

        It sounds like you'll never bump up against the limits of your service capacity, but if you do, there are now EV "chargers" (EVSEs) that monitor the current on your panel feeders, and can throttle back the charging if you are approaching using the full capacity. Wallbox Pulsar Plus is one that's readily available in the US.

    2. Aun Safe | | #22

      Bill, is a 40 space panel the biggest they make for standard applications?

      Is something like this 60-space panel considered to be commercial? https://www.zoro.com/square-d-load-center-60-spaces-200-a-amps-120240v-ac-qo-circuit-breaker-type-qo160m200pc/i/G6179171/

      Suppose you were to find a 60 space residential panel. Does it get difficult to wire them when they start filling up because there are just so many wires going into the panel? A full 60-space panel would obviously have a lot more wires running into it than a full 40-space panel. Makes me wonder if it would get so full and complicated that you might ultimately be better office with a 40 space + a subpanel.

      1. Expert Member
        Zephyr7 | | #24

        The largest standard panel is a 40 space, but there are bigger ones out there like the one you found. Code used to be that 42 spaces was the max, but they got rid of that code a few years ago. I have seen ridiculously large commercial panels (84 space!!!), but I don't recommend those since as you mention, it's a very tight fit inside for all the wires.

        That 60 space panel is a residential panel. It's "residential" because it's 120/240 single phase. Commercial panels are usually three phase, and the number of spaces will usually be divisible by three (which is why commercial panels tend to be 42 space instead of the 40 spaces of a typical residential panel). The reason for this is so that you can get the same number of circuits on each phase for load balancing purposes. Ocassionally a "single phase" residential panel will be used as a small commercial subpanel, in which case only two of three phases is used and you end up with 120/208 single phase power in that panel. Residential service is 120/240 volts because it's two halves of the same phase, which makes the voltages add to 240 volts. With three phase power, there is a 120 degree phase angle so the voltages add vectorily. I like to jokingly say "thar is trig in them thar numbers!" :-)

        Anyway, if you want more than 40 spaces, I would try to get a feedthrough type panel (these have a main breaker but also main lugs on the busbars) so that you can daisy chain a second 40 space "main lug" (which means it doesn't have a main breaker in it) panel onto the first panel that DOES have a main breaker. This gives you 80 spaces, but spread between two panels which allows a lot more room for wiring. You can also use subpanels, which you'd usually feed with 60A or 100A circuits off of the main panel. If you have a large home, putting the subpanel at the opposite end of the house from the main panel can sometimes save money on electrical installation, and can sometimes reduce voltage drop on circuits on that side of the house too.

        BTW, try to get panels with copper bus instead of aluminum. The cost is almost the same, and copper bus is better for long life.

        Bill

        1. Aun Safe | | #25

          Thanks, Bill. Very informative.

  5. Expert Member
    Peter Engle | | #5

    I'd also note that besides going all-electric, you should be planning on using efficient equipment and loads of insulation. As a made-up example, a well-lit large(ish) house using old-school incandescent bulbs might have needed 5-10 20 Amp circuits and when everything was on, they could be pulling 80% of that. With LEDs, the same amount of lighting could be installed on a single circuit, based only on loads. Similarly, a well-insulated house is going to need 50% or less of the (properly sized) HVAC that a typical code-minimum equivalent requires and that translates directly to smaller equipment and smaller loads. Charging EVs overnight has been mentioned before. But even the steam shower, spa, hot tub and sauna are probably not going to be running full-blast at the same time. Certainly not the same time you are running the kitchen at full-tilt. Even there, you can get more efficient equipment that reduces the necessary energy inputs. 400 Amps is enough for all but the largest residences. Still, as Bill says above, your electrician should be performing a load analysis once all of your equipment is specified.

    1. Bernard Lam | | #7

      thank you Peter. The home should be decently efficient just to meet code here. LED lights is a requirement here now. R80 roof, R30 walls, 80G HPWH, 5 head minisplit etc. All electric with a 25kw PV roof, estimated to produce 32000kwh/yr.

      I had assumed that adding the amps of the breaker size required by the equipment was a valid way to give me an idea of how much I'll use, and I thought that I should assume everything can be all on together as a worst case scenario (for code or otherwise). Now I know it doesn't work like that.

      1. Expert Member
        Akos | | #8

        Depending on how your PV is metered, you might need a PV ready main panel. These have a dedicated bus for the PV inverter as a regular panel would be limited to 20% of the panel max current (ie a standard 200A panel is limited to 7.6kW PV).

        There are also other ways around it, just make sure this is figured out before picking equipment.

        You can also put the ADU on its own meter, this way if it is ever rented, billing becomes much easier. Around me you can connect two meter bases/masts to a single overhead feed.

  6. Deleted | | #13

    Deleted

  7. Bernard Lam | | #15

    Funny that you mention crown amps for subs - it's exactly what ive been intending. Currently I have a XLS1500 that I used to push a couple 15"s from partsexpress. Subs and amps are one of those things in life that you don't think you need more until you do. Never thought I'd want more than 1500rms but before you know it the amp was clipping, so this time around I'm going all in, I want lots of headroom at clubbing levels. I'm planning on 2 "bass tower/arrays", 6x 12" or 15" per side. Im one of those people that prefer to have my subs showing and making a statement rather than stealth installs - which I have considered, I.e. having them built into the stud bays. I have a 2x10 double height LVL wall that could take these subs, but every time I think about it, I feel that I don't want to risk the subs cracking the drywall mud from its vibrations. (I attached some pics of this balloon framed LVL wall, which probably should have been done in steel, but that's a different discussion).

    Regardless, i found some XLC2800 for really cheap on eBay - the reason they are so cheap is because they are the 220v "euro" version. But then I did some research and everyone I talked to told me that it should work fine at 240v in the US. Whether it's single phase (euro) or dual phase (us), or 220v or 240v should not make a difference. I was advised to install a 240/20A circuit/outlet with #12 wire, and a 6-15p plug for the amp. Since im running dedicated circuits anyway, 120 or 240 should be similar cost. And the 240/20a outlet can have 2 of those amps plugged into it - each bridged to provide 2400Wrms pushing 6-8 drivers. Very very overkill but in use it might be only drawing 10% of that power. Maybe I'd just do one xlc2800 if im using 12"s and 2 amps if im using 15s.

    You might be interested in this amp too. Just leave a couple for me. Hint: make a $250 offer.

    https://www.ebay.com/itm/CROWN-AUDIO-800W-POWER-AMPLIFIER-XLC2800-brand-new-in-sealed-box-220V-EUROPE-/203250353737?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=711-127632-2357-0

    That's probably too much sound talk for a building site!

    1. Charlie Sullivan | | #18

      I, too, used to work in audio (part time jobs while I was in engineering school, back in the late 80s) and we were proud to have Crown amps in several of our studios. Back then the owner's manual had a full schematic, and I learned a lot from looking at that in detail, and, if I remember right, using it to troubleshoot and repair one that someone blew out.

      Your plans for that should work well.

    2. Expert Member
      Zephyr7 | | #19

      I suggest you look into the Ultimax subwoofers, especially the 18" one, that Parts Express sells. It has an excellent reputation, and you can built it into enclosures with freely available specs online (look up "full marty subwoofer"). There are a lot of places that offer precut pieces of MDF to simply the construction of these. They like a lot of power though! If you're planning to fill that massive room with good bass, you're going to need a lot of power. Years ago I had a theater setup with I think it was four dual 18" EV bass boxes (horns) to play with. It was great for organ music, I always test with Toccata and Fugue in D minor -- I have a great Telarc recording of that but it takes a lot to make it sound right. "Right" is the way it would sound with an air drive pipe organ in a stone church.

      Check out the Behringer NX6000D as a cheaper alternative to the Crown Drivecore amps. The built-in DSP can be used to implement EQ curves and protection filters for your subwoofer to prevent excessive cone excursion, among other things. Very handy!

      You are correct about the power. There is no "dual phase" power, it's just single phase. The two "legs" of our North Americal electrical service are two halves of the same phase, the sine wave on each 120v leg is 180 degrees out of phase with the other leg. That's why the waves in each are additive, giving 240 volts across the two 120 volt legs. The only difference is that in Europe they have 50Hz power where we have 60Hz, but switching power supplies won't care, and it's common for them to be rated "100-250v, 50-60Hz" anyway, so they'll work anywhere. Amps with linear power supplies can sometimes have issues with 60Hz power though.

      A 12 gauge run is fine. For a 240v only circuit, you can use the same 12-2 with ground cable you'd use for a 120 volt circuit since you won't need a neutral. Just tag the white wire with black or red tape on both ends and you're good to go. I would recommed a 6-20R receptacle though, which is a 20 amp receptacle, instead of a 15 amp 6-15R. I'd use a spec grade receptacle too, which is a commerical grade part and will have a tighter fit on the contacts (better reliability). I replaced all the receptacles in my own home with spec grade receptacles in the first month I had the house. Spec grade receptacles also have a better clamp to connect the wires on the back too.

      Bill

      1. Bernard Lam | | #20

        I do love talking about subs. I'm familiar with all the equipment you mentioned. I started with an ultimax 15 in their knock down sealed box, in a small but open plan living room in my current house, powered by the crown XLS 1500. I was a little too liberal with the gain and thought the ultimax can handle it knowing that it's known to be very power hungry. The voice coil burnt up after a few years and a few parties. But that's a single 15, and also in a sealed box - extremely inefficient. So for this much much bigger living room, that's also open to kitchen and dining and stairwell to 2 other floors..... That's why im thinking 2 bass arrays/towers with 6 drivers each side, and lots of power.

        Im no stranger to bass horns either. I built 2 tapped horns, each with a 15" Dayton pro driver, for outdoor parties in the deserts in Utah. I go climbing and throw mini raves at indian Creek a few times a year. Those work really well and would fill my living room with sufficient bass, but only down to 40Hz. That's what they are designed to, since it's pointless to try to reproduce anything less than 40Hz outdoors without stupid amount of power and subs.

        I have looked at the NX6000D and others in the series. Behringer refuses to provide RMS numbers, so im going to guess it's more like a 3000W rms amp. It's going for around $400-500. The XLC 2800 im thinking of getting can be bought for $250 (via link above), because it's listed as a 220V, not suitable for US amp. But I think the seller is clueless and it will work just fine as long as I install the 240v circuit. This amp should be 2400rms. So $/w this XLC 2800 is a really good deal. Obviously no DSP or crossovers, and needs a 1.4v input.

        I have no doubt that a few Marty subs will give me good bass - but these huge rectangular single driver boxes are ugly in a living room, that's why people build them into furniture or the building itself to hide them. I'm more interested in building subs that I can see - which means they have to look good. That's why I think a "slender" line array of 12" may work. I guess if I had prioritized the subs design for the house I should have made the floor plan suitable for an infinite baffle install. Building them into the the balloon framed 2x10 wall stud bays would be a similar concept. But like I said, im worried about rattling the drywall too much! And probably annoy my neighbors more than if they were inside the house (instead of inside the walls).

        4 dual 18 EV bass horns indoors in a residential home would be insane. That's 8x18" drivers, horn loaded. But still, they probably have an F3 no lower than 30 because it's simply impossible to do bass horn much lower without it being the size of a container. These days people are chasing sub 20hz for home theaters. I'll settle for a true 20Hz F3.

        Man, building subs is so much more fun than building house. So much simpler and instant gratification!

  8. Frank Crawford | | #21

    Try to keep the panel as small as possible. Take a look at this pocket guide to electrification. It links to a "watt Diet" calculator. You can use load share devises as well. https://redwoodenergy.net/wp-content/uploads/2021/02/Pocket-Guide-to-All-Electric-Retrofits-of-Single-Family-Homes.pdf

    1. Expert Member
      Zephyr7 | | #23

      There is a lot of bad information in that article. There is also a lot of poorly written statements like this "Keep in mind that a 100 Amp Sub Panel can be served by a smaller circuit like a 50 Amp circuit serving up to 80 Amps of loads because of their already counted diversity.". I'm pretty sure I know what they're trying to say, but the way they say it doesn't really make any sense.

      You absolutely DO NOT want to "keep the panel as small as possible". You want it big. Big is more future proof, and doesn't cost any more to operate -- the purchase price isn't even that much different. For a new home, I would look for 200A service and a 40 space panel. I would never put in a smaller than 40 space main panel, and I'd be very reluctange to put in less than 200A service in a new home, or a major renovation project. A big panel doesn't use any more power than a small one, but it gives you more options in the future should you ever need them. If you have to upgrade the panel in the future because you ran out of space, you're going to be spending a lot on a pretty big electrical "service change" project.

      Bill

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