You have plenty of power at your disposal
Running through the simplified method (NEC 220.82) for each unit in turn and then the commons (house) loads under the following assumptions:
- Each studio is 500ft2 and the commons are 250ft2 (200ft2 laundry room + 50ft2 for any hallways, entryways, etc), leaving 1500ft2 for the main house
- The main house has four kitchen receptacle circuits (treating the dishwasher/disposal and microwave circuits as SABCs, which is often a conservative assumption) + a laundry circuit at 1500VA each
- Each studio has two kitchen receptacle circuits at 1500VA each
- The commons has a single laundry circuit at 1500VA
- The HVAC loads are commons loads, using a 4 ton/48kBTU, 13SEER A/C (Trane XR13) as an exemplar unit drawing 28A@240VAC to provide a "realistic worst case" for a modern air conditioner
- 10800VA (4500VA lights + 7500VA small appliances, 10kVA at 100% demand factor and 2kVA at 40% demand factor) or 45A@240VAC for the main house
- 4500VA (1500VA lights + 3000VA small applainces, all at 100%) or 18.75A@240VAC for each studio
- 8970VA (750VA lights + 1500VA small appliances, all at 100%, + 6720VA (28A * 240V) for HVAC at 100% demand factor) or 37.375A@240VAC for the commons loads
which adds up to 120A for the whole shebang, well under the 200A of power the utility is giving you.
However, you gotta keep 'em separated!
However, your single-panel plan is a non-starter, primarily because NEC 210.25 forbids commingling loads across unit subdivisions, and this will become an issue if you try to sell this place, especially to another landlord. As a result, you'll need to provision for subdivided metering and power, and this will start all the way back at the meter socket, or sockets as the case will be, and continue through the entire electrical architecture of the building.
While there are several different ways of implementing multi-tenant metering (individual sockets or meter-mains on a utility sealed trough, ganged meter sockets, and modular multi-tenant metering solutions), I would recommend a meter-main stack, also known as a meter-pack, for this application as it's a single item (less work for the electrician to install) and makes downstream rearrangement easy as the main breakers are in the meter-pack, making everything downstream all subpanels. In particular, the Eaton 1MP4124R stands out for this application's needs and its versatility to meet local utility requirements:
- It can be field retrofitted for ring-type or ringless meter mounting
- It can be used for underground or overhead (with a DSxxxH2 hub) service
- It can be fitted to meet a variety of local utility specifications, including CECHA and EUSERC
- A copper bus version is available (1MP4124RC) if your AHJ has an aluminum allergy
- The bottom meter socket can be blanked out with a 1MMBC125B, allowing it to provide 3 meters now while having expansion room for a separate commons meter later
- And, it uses readily obtainable type BR breakers for the tenant mains
As to what goes inside this meter-pack, your electrician should be familiar with what the local utility wants for metering, but we can specify the tenant mains now: a BRH2125 for the house and a BRH2100 per studio (2 total). The fourth tenant main is left unpopulated to provide future provision for separating the common area loads onto their own meter, or you can specify a BRH260 there if you want the common area loads on their own meter from jump. (The H in these stands for a higher fault current interrupting rating -- BRHxxx breakers can break a 22,000A short, while ordinary BRxxx breakers can only open a 10,000A short. I'm specifying the BRH here to provide an appropriate safety margin against utility upgrades that increase the fault current on your service -- modern main breaker residential panels specify a 22,000A interrupting rating on their main breakers as a bare minimum.)
From there, we move onto the feeders that go off to the individual dwelling unit panels, as well as the grounding electrode conductor, which routes through one of the small knockouts on the bottom center into the bonding block located there. Instead of running separate cables or conduits to each panel, though, we use conduit nipples to run the feeders into a 6" by 6" metal trough (gutter, wireway) with field-made knockouts (factory KOs on a wireway this size are too small for our usecase) mounted below the meter-pack and extending out to the right (so it doesn't get in the way of where an underground service goes into the meter-pack, or where the grounding electrode conductor goes for that matter). Furthermore, these feeder conductors are smaller than expected, as the rules in NEC 310.15(B)(7)(2) apply, which allows them to be downsized to 83% of what they would otherwise be, just like service conductors, as they carry the entire load of a dwelling unit each.
As a result, the main house feeder consists of 3 1/0AWG XHHW-2 aluminum wires, each studio feeder consists of 3 2AWG XHHW-2 aluminum wires, and the common-loads feeder consists of 3 6AWG THWN copper wires as it can't be downsized. This means that a pair of 2" nipples can be used, with one carrying the main house feeder with room left over for the common loads feeder, and the other carrying the two studio feeders.
Attached to the trough using more of the 2" nipples from above are the panels for the various dwelling units involved, which are all main lug panels configured as subpanels (i.e. neutral and ground bars separate) in NEMA 3R (outdoor) enclosures:
- The main house should use at a minimum a 42 space panel -- this puts you into 200A or 225A bussing, but that's what you need to get the kind of space you're after, and doesn't pose any issues electrically speaking. A 54 or 60 space panel would not be amiss here whatsoever, though!
- The studios don't need so many circuits, so a 30 space, 125A panel can be used for each studio, although if you wished to put larger panels in for them, feel free to be my guest.
- Last but not least, the subpanel for the commons loads can be another 30 space, 125A unit (or larger, depending on what was used for the studios). If you didn't spring for the fourth meter+main initially, then this panel is fed as a subpanel off of a 60A, 2-pole breaker in the main house's panel, thus making it so that the commons loads are on the main house (this may be what is expected for accessory dwelling units in your area, check with your AHJ for details). If you do wire it this way, make sure to route the feeder for this subpanel back into the trough from the main house panel via the same nipple the feeder for the main panel came in from instead of a separate conduit or cable.
As to the make and model of panels to get, Siemens PL stands out as an obvious first choice (copper bussing, factory ground bars, 54 space options, and all this for a reasonable price), with Eaton BR as a backup plan in case you don't have a Siemens supplier in your area or your AHJ needs the series combination rating with the BR tenant mains in the meter-pack, as series ratings like that don't work across breaker manufacturers. You may be able to repurpose your existing panel as a secondary feedthrough off the house main using a set of subfeed lug blocks and some more of that 1/0 Al in conduit as a feeder, though, so don't have the electrician trash it!
If your AHJ has other ideas...
It may be the case that your AHJ requires accessory dwelling units (like your studios) to be on the same meter as the main dwelling. In that case, I'd still use the four-panel setup as before, but instead of feeding them from a meter-pack with individual meters, I'd instead use one of two configurations:
- A rule-of-six meter-main such as the Eaton MB1212L200BTS, main breakered as above, with a separate main for the common loads panel. This has the advantage that individual tenants (or the common loads) can be turned off without disturbing other tenants, but has the disadvantage that there's no single shutoff means (some AHJs or utilities require a single-handle main disconnect), and it also makes feeding 200A to the main house more difficult (especially in EUSERC areas, as the MBE1212L200BTS doesn't support BJ branch breakers for feeders >125A). It also only comes in aluminum bussing, which is a problem for some rather skittish AHJs, and has few bypass options, which is troublesome for some utilities.
- A single-disconnect, 8/16 space, feed-through lug equipped meter-main such as the MB(E)816B200BTS, again configured with the same feeder breakers as before including a separate common-loads main. This has the advantage of providing a single shutoff means as well as a clean path to providing 200A to the main house, but has the downside that providing 200A to the main house means that shutting off the main house shuts off everything else as well (as you need to use the feed-through lugs to do that). It also has the upshots of being available in copper bussing and a wider variety of bypass options, as well as being easier to make EUSERC compliant.