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I am replacing all of the electrical in my house and am upgrading from a 200amp service to a 320amp service. We are in an unicorporated area of the county so there will not be an inspection but I still want to do things safely. Before I purchase thousands of dollars worth of equipment and wire I want to make sure that my plans are good. Any advice is much appriciated! Here is what I am planning.

There will be 2 200amp breaker panels in the house (one about 30ft from the meter base and another about 80ft). To safely power each panel, I would connect the two hots and neutral from the meterbase and run those a few feet through conduit to a 200amp disconect use 4/0 AL wire. Since each of the disconnect boxes are the first point of disconnect I would have the netrual and ground bonded in each of the boxes. From each of the disconnect boxes I plan to run 4/0-4/0-4/0-2/0 AL SER cable thorugh the attic (not in conduit) to each of my breaker panels. In the panels the netrual and ground would be disconnected.

One question I have is can I use the same two grounding rods to ground both of the disconnect panels or do I need two rods for each panel?

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    If any advice is truly appreciated, I'll tell you what my approach would be: hire an experienced electrician to do things that, as an enthusiastic DIY-er, you will never have the opportunity to practice and become good at. Upgrading your electrical service is perhaps the poster child for this. It happens once per lifetime per house, and each house is different. The only way to gain experience is to do lots of houses, tutored by an expert. You seem to know a lot, and could probably do a good job, but why? As you say, it's a lot of expensive gear, and maybe one day of work for a pro.
    – jay613
    Commented Sep 27, 2023 at 12:39
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    You can buy one box, a "meter main", that contains the meter and both of your disconnects (breakers). Note, with two 200A subpanels, you'll have to choose how to split 320A, you cannot put in two 200A breakers. Needs planning. You can also run your A/C compressors and any other large outdoor thing directly off the meter main, and then use smaller breakers for the two panels.
    – jay613
    Commented Sep 27, 2023 at 12:56
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    @jay613 not true. A class 320 meter is 320A continuous rated. i.e. 400A * 0.80 derate factor. It's normal, acceptable, and expected to run 2X 200A from that, as each should only be provisioned with 160A of calculated loads, since those are not continuous rating like the meter. But indeed, if a meter-main or ranch panel can be found that fits the utility's requirements, that saves a lot of bother with extra boxes.
    – Ecnerwal
    Commented Sep 27, 2023 at 13:57
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    @jay613 that particular one has already been asked and answered: diy.stackexchange.com/q/192922/18078
    – Ecnerwal
    Commented Sep 27, 2023 at 14:25
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    @ThreePhaseEel I am using this load calculator that I found. ask-the-electrician.com/… The numbers below are what I am plugging in. There isn't a place to factor in the tankless water heater so I am entering that in with the HVAC calc. • Square ft = 2700 • Countertops and Islands 3: 4500 • Laundry: 1500 • Washer: 1500 • Fridge: 1500 • Dishwasher:1500 • Microwave: 1500 • Pantry Freezer: 1500 • Oven: 8000 • Cooktop: 12000 • EVSE: 9600 • HVAC: 14400 • TL Water Heater: 36000
    – Houston
    Commented Sep 28, 2023 at 13:01

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If EVs are the only reason for the service upgrade, don't. EVs don't need service upgrade because of energy management systems.

Now the first issue is that both of your service lines need to enter the house together at the same location, and have disconnects (optionally: main breakers) there. See 225.30 in NEC 2020.

It's perfectly fine to label these "Service Disconnect" and label the ones at the meter "Emergency Disconnect - Not A Service Disconnect". Then you won't need to run 4-wire between them and can do your master neutral-ground bonding here. The utility may still require neutral-ground bonding out at the meter.

NEC 310.15(B)(16) states clearly that 4/0 is only 180A wire. You would need 250 kcmil off a service that is larger than 200A, since 310.15(B)(7) does not apply.

Yes, disconnects at a given location can share ground rods.

It's valuable to think about future generator, PowerWall or V2X. In 2-panel 400A service, there is no easy way to feed those things to both panels. You would need a 3-pole 200A isolation switch or transfer switch on one of them (otherwise you create a dangerous neutral loop). Generally it's simpler to pick 1 panel and put all your critical loads on that.

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