Okay, let's break this down. You're on the right track, but there are a few nuances to consider when dealing with multifamily dwellings and service sizing.

Understanding the NEC and Load Calculations

The National Electrical Code (NEC) provides the rules for calculating electrical loads. It's designed to ensure safety and prevent overloading. You've already taken the important step of performing a service load calculation for the entire building, which is crucial.

Why You Can't Simply Divide the Total Load

While dividing the total calculated load by the number of units seems logical, it's generally not the correct approach. Here's why: Diversity

Not all units will be drawing their maximum load simultaneously. This is known as "diversity." The overall service calculation accounts for this, and that's why it's likely significantly lower than 4 times your individual unit calculation.

Code Requirements

NEC Article 220 outlines the specific methods for calculating loads, and these methods often include demand factors that account for diversity.

Individual Needs

While the diversity factor in the overall calculation exists, you still need to ensure each unit has enough capacity to handle its potential maximum load.

Analyzing Your Calculations and the Service Equipment1. Your Overall Multifamily Calculation (380 amps)

This is your total service requirement. This is the load your service entrance conductors and main overcurrent protection device (the breaker feeding the meter bank) must be rated for.2.

Your Individual Unit Calculations (90-123 amps)

This gives you a range of the potential load for a single unit. The difference between the standard and optional calculation comes from different methods of estimating the load of the units. The standard method is usually higher because it assumes the loads of certain items, such as cooktops, or dryers, are all on at the same time, while the optional load calculation method allows you to include demand factors in the calculations, which might give you a smaller value than the standard method. Both methods are correct and accepted. It is up to you to choose which one you feel is more realistic for the loads of the dwelling units.3.

Square D MPH44125 Meter Center

This is a critical piece of information. You state the pedestal is rated at 125 per position. This tells us that each meter socket (and therefore, each breaker feeding each unit) cannot exceed 125 amps.

Can You Install 4 - 125 Amp Panels on a 400 Amp Service?

Yes, assuming your 380 amp multifamily service load calculation is accurate and based on the NEC. Here's the reasoning: Code Compliance

The NEC allows for the sum of the individual unit breakers to exceed the main service breaker because of the diversity factor.

Protection

The 125 amp breakers at each meter position protect the individual unit feeders and panels from overloading.

Service Size

Your 400 amp service is sized based on the calculated load for the entire building, accounting for the fact that not all units will be drawing their maximum at the same time.

Recommendations1. Verify Your Multifamily Load Calculation

Double-check your multifamily load calculation (380 amps) to ensure it's accurate and complies with NEC Article 220. Make sure you've included all relevant loads (lighting, receptacles, heating/cooling, appliances, etc.) and applied appropriate demand factors.
2.

125 Amp Panels in Each Unit

Given the limitations of the meter center (125 amps per position), installing 125 amp panels in each unit is a reasonable and likely code-compliant solution. This provides a safety margin over your individual unit load calculations and allows for future expansion within the unit.3.

Feeder Conductor Sizing

Make sure the feeder conductors (wires) running from the meter center to each individual unit's panel are properly sized for the 125 amp breaker, according to NEC Table 310.16 (or the appropriate table for the conductor type you're using).
4.

Local Inspections



Crucially, consult with your local electrical inspector before starting the work. They have the final say on code compliance, and they may have specific requirements or interpretations that you need to follow. They may also want to see your load calculations.

In summary: You're on the right path. Using 125 amp panels in each unit, fed from the meter center, is likely acceptable if your overall service load calculation is accurate and complies with the NEC. However, always consult with your local electrical inspector before proceeding.Good luck with your project! Flag for review