I'm in the process of upgrading my electrical service from 200 amps to 400 amps (technically 320A continuous). My electrical utility is Puget Sound Energy (PSE) in Washington State.

Although Washington has adopted the NEC 2020, I spoke to an inspector in my AHJ who said they are not enforcing the new rule-of-six disconnect rule change. Nevertheless, I was originally intending to install a Siemens MC2442B1400SDL (as suggested by someone on this site), which is a meter-load center combo which large single 400A main breaker, which would satisfy the rule. However, with the COVID supply chain issues, that specific product has been backordered for over half a year. I'm looking into alternate options; such as getting a separate meter socket and load center.

My question is, the options for a 400A load center seem pretty sparse. Should I be looking at panelboards rather than load centers if I want a 400A main breaker? Would it be strange to see in a residential setting?

I'm also a bit confused about how they call it 400A service, but then they clarify it with 320 continuous. Is a 400amp breaker OK in this case, or would they be looking for a 320A service disconnect?

  • 1
    It might not even be COVID supply issues; lots of things in manufacturer catalogs are functional unobtanium. Eaton has a theoretically-fabulous AFCI breaker solution for dorms and hotel rooms to allow tenants to self-reset; vaporware. Commented Jan 10, 2022 at 19:59

1 Answer 1


NEC applies a 125% derate to many loads. Get a 2000 W heater, you must provision 2500 W of power to it. Get a 40A EV charger, you must provision 50A breaker. Get used to it.

If you get too used to it, you just start slapping 125% on everything LOL. At that point, it becomes the same as an "80% derate" i.e. get 100A of service you can only hang 80A of stuff on it.

In industrial gear (which you really, really, really do not want to pay for), equipment is often 100% rated. If the pump nameplate says 550A, you run 550A to it. This is how the power company is used to thinking. So to them, NEC 400A is really 320A. That's all there is to it. Don't worry about it.

Dual 200A panels is how 400A is done.

It's always been done as dual 200A service panels. Simply use two $150 200A service panels. That with a $250 meter pan. And you're done. This should inform your price expectations.

In fact, almost all 400A residential meter pans are manufactured for that use only. They hav double lugs intended for double wires <= 300 KCMIL and they are not certified for paralleling. The only legal connections are to <250A panels, so either one 250A or two 200A.

And this is a conceptual leap that many "400A service" novices struggle with. We had one a couple years ago who was rich, had no frame-of-reference for cost... and refused to hear the above. Hellhound and determined to get a single 400A breaker. Paid for it, and didn't care.

Must be nice, but think of all the safety improvements that waste could have paid for.

There is no consumer-tier 400A main breaker or service panel realistically on the market. By "consumer tier" I mean "made in 10 million quantity with economies of scale driving the price down to an affordable number", not reflective of quality.

How "outside disconnect" changes things

As said, the relevant change in NEC 2020 is that houses need outside disconnects. This is so fire departments can de-energize entire houses in a hurry and for sure. (this is especially important for Rapid Shutdown of rooftop solar.) In many jurisdictions, outside disconnects have been legislated for 50 years. It's just NEC "catching up".

Without outside disconnects: you would buy a meter-pan with dual lug terminals rated for two 300 KCMIL wire, and run totally unfused 4/0 wire a very short distance ** to each of two 200A "main breaker" panels typically indoors. This is not paralleling.

With outside disconnects: you would buy a meter-main (pan + main breaker combo) with dual 200A main breakers (<$500*). From there, breaker-protected 4/0 wire runs any distance to each of two 200A "main lug" panels typically indoors ($110).

That is most likely what you would do, unless you have fancy requirements.

Fancy mode: Use (what I call) a "Ranch Panel" or "Farm Panel" ($650*). It has a meter pan + dual 200A main breakers + 8 breaker spaces. It wires exactly as the above: each 200A breaker feeds fused 4/0 wire going to a 200A main-lug panel. Here's the twist: One of the 200A main breakers also feeds the 8-space mini-panel. Off that mini-panel, you run feeder to various outbuildings: well-house, barn, shop, pool house etc. See why I call it a ranch panel?

In fact, some people take the dual 200A and send it to different buildings. The exclusive 200A goes to the farmhouse. The tapped 200A (shared with the 8-space panel) goes to the shop. They didn't get 400A because their house needs it; they got it because it's cheaper than two 200A services.

Still cheap compared to what an industrial 400A breaker and industrial 400A-bussed load center would cost (that would likely take bolt-down breakers anyway).

Allows you to preserve your existing main panel.

The Dual-200A approach allows you to keep your original 200A panel exactly where it is, and leave all the existing circuits in them. That's a whole bunch of re-wiring money you don't have to spend. So that is back in your pocket to spend on stuff that matters.

Then, you simply mount a second 200A panel next to the first one (or anywhere, really; you're no longer chained to the meter because the feeder line is circuit breaker protected.) And that panel sits there empty until you're ready to add additional loads, and there you are!


You mention in comments that you have a 15KW solar system. Your rationale for wanting to force a 400A breaker/bus is it will support more solar, because main breaker + solar can be 120% of bus rating (480A giving 80A solar). That math is wrong.

I know it's wrong because you already have a 200A main panel and already have 63A of solar. A typical 200A panel is 225A-bussed; 120% is 270A, minus the 200A breaker leaves 70A for solar (17 KW). A 15KW solar system is 62.5A (remember: don't derate this!).

It sounds like you "maxed out" your solar capacity, which suggests to me that you'd have preferred to install even more. Well.

If you go with the normal/cheap dual-200A solution, guess what. You keep your original 200A panel and its 70A solar headroom. You get another 200A panel with another 70A headroom. So the plain/traditional/cheap setup actually supports 140A of solar.

So traditional beats the $4000 industrial panel by almost double.

Now at $1500, some make 400A "solar ready" ranch panels of the "dual 200A" persuasion. These have a third breaker space allowing up to 200A of solar, which isn't fed into either panel so the 120% stuff does not apply.

Anyway, I doubt NEC really means that.

Because of the above, I do not accept or believe the NEC 2020 requirement. Never in NEC's history has it "obsoleted with the stroke of a pen" billions of dollars of inventory and planned production. They have always spent many years soft-walking every major change into the marketplace. The fact that the "supposedly required" new stuff isn't even available... plus no way will builders allow a $4000 requirement on every house to become law. This tells me this is some sort of clerical misunderstanding, and NEC doesn't really mean to ban 2x200A type meter-mains.

(Besides, if they really wanted to mandate a single switch throw, it would be trivial for manufacturers to alter their dual-200A meter-mains so a handle-tie kit could be installed on the 2 breakers.)

* bare cost will be less, but it will come with one main breaker unpopulated [since you might have 300A or 350A service]. I am allowing for the cost of the second breaker which is field-installed. Set torques correctly.

** In an old style meter and main panel, the run between the two is completely un-fused. It has no overload or short-circuit protection at all. If it took damage, it would dead-short at 10,000 amps and burn your house down. As such, Code requires that cable run be as short as possible to minimize risk.

  • Thanks for the detailed answer. One further question -- I have a 15kW solar system that's load-side backfed into an 80A breaker. If i had a single 400A busbar, I would be able to have a full 400A breaker + 80A backfed breaker (400 * 1.2 = 480). With a 225A busbar, I'd have to derate one of the panels to at most 175A (practically 150A since siemens doesn't make a 175A MBK-series main breaker). If I really wanted the full 400A load (even though I doubt I'd need all 400 at once), I would have to put in a 400A busbar panel somewhere in my setup, right? (1/2)
    – atanamir
    Commented Jan 10, 2022 at 23:09
  • (2/2) If that were the case, would having the 400A panel result in the fewest number of panels on outside of my house, for aesthetic reasons? 400A breaker, 200A branch to house, 200A branch to an ADU, 40A branch to my well shed, and 80A backfed solar. (@ThreePhaseEel may remember; he helped me with this whole setup).
    – atanamir
    Commented Jan 10, 2022 at 23:10
  • I've actually looked into handle-tying dual 200A disconnects together but the issue is that nobody makes a handle tie identified to fit on "main frame" 200A breakers, or even the double frame types in some/many cases... Commented Jan 11, 2022 at 1:12
  • "each 200A breaker feeds fused 4/0 wire" -- by "fused", do you need it needs a fused AC disconnect?
    – atanamir
    Commented Jan 11, 2022 at 2:06
  • 1
    No, "fused" in that sentence just means "protected". It doesn't refer to actual fuses. The breakers are the protection.
    – nobody
    Commented Jan 11, 2022 at 2:28

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