GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Largest Possible Residential Electrical Panel

blamus20 | 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.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  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. joenorm | | #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
    BILL WICHERS | | #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.


    1. blamus20 | | #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


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

        1. blamus20 | | #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


            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
        BILL WICHERS | | #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.


        1. blamus20 | | #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.

      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. aunsafe2015 | | #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?

      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
        BILL WICHERS | | #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.


        1. aunsafe2015 | | #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. blamus20 | | #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


  7. blamus20 | | #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.

    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
      BILL WICHERS | | #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.


      1. blamus20 | | #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. frankcrawford | | #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.

    1. Expert Member
      BILL WICHERS | | #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.


  9. tundracycle | | #26

    Old discussion but for others who might stumble on it… Xcel offers a Time Of Use (TOU) service that works well for charging (EV's, etc.). Much lower rates during off-peak (though much higher on-peak so be careful). We have 400a main + 200a TOU. TOU serves EV chargers and boat charger as well as outlets in garages for charging mower and other stuff.

    We also have solar that feeds in to the 400a meter base (if you feed it in to the TOU base they will always pay off-peak rate so you don't want to do that).

    1. nachenklich | | #27

      I assume that is Colorado? I am in California. Are there other utilities that offer TOU or is that a unique offering, unique to XCEL which I assume is Colorado?

      1. tundracycle | | #28

        We're in MN. I believe many/most utilities offer TOU.

    2. Expert Member
      BILL WICHERS | | #29

      My utility calls this a "Time of Day" rate, but the same basic concept. There may be some other names for it out there, so anyone interested in a such a rate will probably need to read up on the rates from their utility to find it. This is a very common rate, and has been the standard for larger commercial services for decades -- it's only new for residential users.

      I have my entire house on this rate. On-peak for me is 11am to 7pm weekdays, off peak is 7pm to 11 am weekdays, and all day weekends and legal holidays. I typically save around $30-50 per month on this rate compared to the normal residential rate. My EV is set to start charging when we get to "cheap power time", and we try to do our laundry and dish washing during cheap power time too. Some thermostats will also optimize heating and cooling around this type of rate structure.

      BTW, in terms of "greeness", the off-peak rate tends to be when load is light, and only the most efficient base load plants are operating to provide that power. That means you're likely to be using power that resulted in lower levels of emissions compared to peak time power, with the one exception of solar that is typical the opposite in terms of when it's producing, but in most of the country solar is a very small percentage of the overall generation mix.


      1. mattlope | | #30

        Hi Bill, I've been building my house for several years now and am at the point I need pull the trigger on ordering all the electrical (which led me to this discussion). You mentioned possibly eyeballing the original poster's one line diagram and was curious if you could possibly do it for mine?

        If so, it looks like I can attach it to one of these replies, would that be the best way?

        I appreciate the thoroughness of your explanations and thought I would reach out. I understand if you don't have the time or desire, thanks either way.


        1. Patrick_OSullivan | | #31


          While various folks here can eyeball certain things and in most cases give advice as to the overall soundness of something, your local codes and norms come into play too. I'm sure if you post some details, folks will be happy to chime in, but just recognize that there's no substitute for someone familiar with your locale.

        2. Expert Member
          BILL WICHERS | | #34

          You're probably better off starting a new thread for your own project and not adding to this one. Go ahead and post your drawing though and I'd be happy to take a look at it. Note that that there can be some variation between local codes, and I am only familiar with the areas I normally work in, but most of the "big" requirements are the same everywhere as the national electric code tends to be adopted in most areas with only minor modifications, if any.


  10. frankcrawford | | #32

    For multiple cost and environmental reasons try to maintain a 100-amp 240-volt electrical connection to the grid. You can fully electrify a home and do this. You may need to use "load-share devices" or "circuit pausers" or "smart electrical panels", but it can be done, even in cold climates like Alberta Canada.
    It is fairly easy in new homes, just make them energy efficient to start. It can also be done as part of a Deep Energy Retrofit, but upgrades to the building envelope are most often required in colder climates.
    The can help.

    1. Patrick_OSullivan | | #33

      Why would you want to limit a connection to 100 amps when 200 amps is the de facto standard? It's simply a practical consideration. Load centers with a 100 amp main breaker have too few panel spaces for even modest houses wired in a careful way.

      Why do you suggest it's a cost savings? It's a rounding error in the grand scheme of things, and instantly voided the second you need to add a sub panel because your 100 amp/20 space panel is too small.

    2. Expert Member
      BILL WICHERS | | #35

      No, do NOT do this. There is NO enviornmental reason to try to stick with a 100A electric service -- doing so accomplishes nothing but artificially constraining yourself and limiting future options. The cost difference between the two usually isn't all that much either: panels usually cost within $20 or so of each other, assuming the same number of breaker spaces, labor is pretty much the same, and all that you're left with as a cost difference is going up a few sizes in wire. The extra cost for the larger service will be far less that the cost for fancy load shed devices.

      Load shedding devices in a panel don't help the grid anyway. All those devices do is shift your loads around in time, so you use the same amount of energy, but you spread the loads out over time. This accomplishes nothing for the grid, since the grid itself already serves to provide this function, since the loads of the many, many users on the grid tend to already spread themselves out over time. This is why the total load on the grid tends to be a pretty smooth curve throughout the day, while all the individual connected services will have large swings as loads cycle on and off.

      I would still do the energy efficiency stuff like adding insulation, but I would never install less than a 200A service in a new home. If you want to add solar, a 100A panel introduces even more limitations. Never intentionally go small on a panel, there is zero enviornmental reason to do so, and the initial cost savings isn't as much as you might think.


  11. nachenklich | | #36

    200A seems the standard for what is used for sub panels in single family homes and 400A service. I'm having a really hard time finding the panels I am looking for. Most of them are backordered for months. There is the new Siemens line of NEC 230.71 compliant solar ready meter mains which are nice But seems they won't be available until July at least. I was looking at the MC3042S1400FCS but that has only 30 breaker spaces and I need at least 4o, like 42 or maybe even more if possible. So maybe I am looking at just a Meter/Main breaker panel and then go to 2 200A subs with at least 42 breaker spaces each. But even those are hard to find.

    1. Expert Member
      BILL WICHERS | | #37

      All electrical switchgear has been on a much longer leadtime than usual. I had one panel (a 600A 480V commercial panel) that I ordered last March that just came in this month. That was a Siemens panel too. Siemens has been a little better than Square D and Cutler Hammer in terms of lead time, but all of them are way behind compared to what they used to be.

      If you need more breaker spaces, you could daisy chain panels. What you are thinking of as "subpanels" are normally called "main lug" panels. The only difference with a "main lug" panel is that it doesn't have a main breaker in it, the supply wires go directly to the busbars, since the main disconnect for such a panel is located someplace else. You will often still need the ground bar kit though, since the ground and neutral busbars must be isolated from each other in panels fed this way per code. You can get two 40 space panels and use one feeder to feed both of them. You can get panels with lug in and lug out (main lugs at the top and bottom of the busbars), but it's probably easier to use what are commonly called "clear taps" to act like huge wirenuts to allow you to splice both panels into a single feeder using a large junction box. Don't use split bolts and tape for these connections, clear taps are very much better, and safer over the long term. When you feed two panels from one feeder like this, both panels must be rated for the full ampacity of the feeder (i.e. two 200A panels on a single 200A feeder, you cannot use two panels rated for less than 200A on a 200A feeder), and the capacity of that feeder is then shared between the two panels. This is done commerically when more space is needed, but you don't see it done very often on residential installations.


  12. nachenklich | | #38

    Thank you for those great details. Interestingly I didn't find much googling "clear taps" but I get the concept. I'll ask my electrical distributor if they have those available and consider using them. Or daisy-chaining a bunch of MLO panels is probably the easiest route. I also would need a 200 Amp breaker per MLO panel to protect the feeder wire which technically would make it a MBR panel. So I guess you use MLO panels strictly - without a breaker - only if the main breaker is not larger than the sub panel capacity, like 200 Amp main and sub panels?

    1. Patrick_OSullivan | | #39

      I think Bill means something like this:

      I've only used black ones, colloquially known as Polaris connectors (as Polaris is a popular manufacturer of them).

    2. Expert Member
      BILL WICHERS | | #40

      Patrick is correct, "Polaris connector" is another name for these things. "Clear tap" is sort of a trade name used around this area.

      You don't need a main breaker per panel with multiple panels sharing one cable, and you CANNOT tap multiple main breakers off of one cable that comes directly from the meter! What you MUST do, is have an UPSTREAM main disconnect next to the meter (or in a seperate panel feeding the other panels). That upstream breaker protects the feeders, then you can tap several panels off that cable, none of which need additional "main" breakers -- the upstream breaker protects the feeder and all the panels. The reason all the panels have to be rated for the full capacity of that feeder is because the upstream breaker is doing the "work" of protecting things, so everything downstream has to be able to handle whatever the rating of that upstream breaker is.

      If you go to any larger commercial building, you'll find that most breaker panels don't have main breakers in them. The reason for this is that there is a BIG panel somewhere that has BIG breakers in it, with a breaker feeding all those distribution panels scattered around the building. That 600A panel I mentioned is one of those panels, feeding several transformers and some other panels downstream of a large UPS system. This is very commonly done in commercial buildings (aside from the big UPS that is :-).


  13. WDShepherd | | #41

    This is a really interesting thread. We have a 2900 sft 5 br 3 bath house with 2 ev. On our future roadmap, we want a steam shower and level 2 ev chargers, plus I'm building a shop, and we'd like to put in tankless Electric water heaters because Oregon is phasing out natural gas. We have a 1970's home with a 100A panel. From the discussions above, it sounds like I could still get away with a 200A panel, even with the electric water heater, but I want to get the most future proof out of my upgrade investment so I'm wondering if I should still put in a 300A panel. Is that overkill?

    1. Expert Member
      BILL WICHERS | | #42

      That tankless water heater will be your biggest problem. I'd either stick with natural gas for that if you have it available (the 'phaseouts' are typically for new connections only), or go with a tank-type electric water heater. Tankless electric water heaters can cause a number of problems for both the home and the surrounding grid, and are really not an idea way to go. In many areas, you'er actually better off from an overall energy use / emissions standpoint burning natural gas to heat water than you are using electric resistance heat.

      Your next biggest loads are those EV chargers. Your shop is probably not a big problem, since those will likely be intermittent loads of relatively short duration when running. Depending on your shop plans, I'd run either a 60A or 100A 240V circuit to a subpanel in the shop. If the shop will be a remote building, BE SURE to size the feeder for volt drop!

      You'd be better off with a pair of 200A panels and not a single, larger panel. I don't think you can get a "300A" panel either, the usual step is 200A to 400A. You can feed two 200A panels from the "400A" (actually 320A) meter base, or use a 400A panel with a few large breakers in it to feed a number of 100A and 200A subpanels.


    2. tundracycle | | #43

      For your EV's look at a Time Of Day meter (and separate breaker panel). In our case the overnight rate is about half the standard rate (but the day rate on that meter is about twice the standard rate so you only want to use it during off-peak at night).

  14. WDShepherd | | #44

    Thank you both. That's very helpful.

  15. GilesM | | #45

    I realize it's not normal but our house (Oregon) has 2,000 amp service. We have a steam, sauna, jacuzzi and pool as well as electric HVAC and water heaters plus a fair amount of square footage. Solar defrays our costs. A generator would be nice but I hesitate to imagine the size required.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |