Okay, let's break down the best approach to integrate that 12kW PV system, considering your constraints and code compliance. The key here is to ensure safety and adhere to the NEC (National Electrical Code).Here's a breakdown of the options and the recommended approach

Understanding the Problem & Key Considerations
PV Size and Backfeed Limits

A 12kW PV system is substantial. Your concern about exceeding the 120% rule on the 60A shed panel is valid. The 120% rule (NEC 705.12) states that the sum of the overcurrent protection device (OCPD) protecting a busbar plus the inverter output current cannot exceed 120% of the busbar's rating. In your case, 120% of 60A is 72A. Let's assume the existing breaker in the shed panel is 60A to feed the shed. The maximum backfeed you could theoretically have through a breaker is 72A - 60A = 12A. A 12kW PV system will likely exceed that (12kW / 240V = 50A, plus a 1.25 multiplier for continuous output, it's 62.5A) which is well beyond 12A.

Main Lug Only (MLO) Panel

The fact that the shed panel is MLO (Main Lug Only) means it doesn't have a main breaker. This further restricts the ability to backfeed through a breaker in that panel.

Distance

Several hundred feet to the meter is a significant distance, which will impact voltage drop and conductor sizing.

Analyzing the Options & Recommended Solution

Here's a breakdown of the options you presented, plus some additional considerations:1. Tapping PV Disconnect Directly to the Shed Feeder (Between the Garage and the Shed)

This is a complex solution. This is not recommended, as it is not a code-compliant solution. If you make such connection in the middle of a feeder, there's no way to properly protect the conductors or equipment between those tap points. Feeder tap rules are specified in NEC 240.21(B), the tap conductor need to be properly sized and protected, the tap can't be longer than 10' or 25' depending on the overcurrent protection, which is impossible in your case.
2.

Running New Conductors to the Meter

This is the

RECOMMENDED solution, but requires careful planning. NEC 705.12(D) Supply Side Connection

This section of the NEC allows for connecting the PV system on the supply side of the service disconnecting means. In practical terms, this usually means connecting at the meter or ahead of the main breaker in the garage. This avoids the 120% rule limitation within the panelboards.



Pros

Most compliant with the NEC. Avoids any limitations imposed by the shed panel's busbar rating or its MLO configuration. Provides a clean, dedicated path for PV power. Can be designed to handle the full output of the PV system without oversubscribing existing circuits.

Cons

Longer conductor run, meaning higher material costs and potential voltage drop issues. More labor intensive. Requires careful coordination with the utility company (they own the meter and the connection point). May require trenching and conduit installation, depending on local codes and site conditions.

Implementation


Consult with the Utility

This is the first step. They will dictate the exact point of connection, metering requirements, and any specific equipment they require. They might require a new meter specifically for the PV system, or they might allow net metering with the existing meter.2.

Determine the Point of Connection

Based on the utility's requirements, identify the physical location where the PV conductors will connect. This will likely be at the meter or a nearby disconnect switch provided by the utility.3.

Size Conductors and Conduit

Properly size the conductors based on the PV system's maximum output current (12kW / 240V = 50A x 1.25 = 62.5A) and the distance to the connection point. Use appropriate voltage drop calculations (a 3% voltage drop is generally acceptable). Choose the correct conduit size to accommodate the conductors. Remember to use THWN-2 or XHHW-2 conductors for wet locations (underground conduit).4.

Install Conduit and Conductors

Run conduit from the shed (near the PV disconnect) to the meter location. Pull the appropriately sized conductors through the conduit.5.

Install Disconnects and Overcurrent Protection

Install a properly sized disconnect switch at the shed near the PV array. Install an overcurrent protective device (fuse or breaker) at the point of connection to the utility's service, as required by code and the utility.6.

Bonding and Grounding

Ensure proper bonding and grounding throughout the system, according to NEC Article 250. This is critical for safety.
7.

Inspection

Have the installation inspected by a qualified electrical inspector to ensure compliance with all applicable codes and regulations.

Why Other Options Aren't Good

Backfeeding the Shed Panel (Even with a Breaker Change)

Even if you could theoretically install a smaller breaker in the shed panel, the 60A busbar rating is still a limiting factor. You're essentially trying to force too much current through a bottleneck. This can lead to overheating, premature failure, and potential fire hazards.

In SummaryWhile running new conductors to the meter is the most involved option, it's the safest, most code-compliant, and most reliable way to integrate a 12kW PV system into your existing setup. It avoids the limitations of the shed panel, ensures proper overcurrent protection, and allows for future expansion if needed.

Crucially, start by consulting with your local utility company to determine their specific requirements for connecting to their grid.* This will drive the rest of your design. Flag for review