Maryland PSC Level 1 COMAR 20.50.09.09: Interconnection Guide for Small Generators

Key Takeaways

• The 15 percent radial peak load screen limits aggregate generation on a circuit (August 2026).
• The 20 kW shared secondary limit applies to aggregate generation on shared secondary lines (August 2026).
• Utilities must confirm application completeness within 5 business days (August 2026).
• Permission to Operate (PTO) is issued within 20 business days of acceptable documentation (August 2026).

What is the Maryland PSC COMAR 20.50.09.09 Level 1 Interconnection Guide?

The Maryland Public Service Commission (PSC) COMAR 20.50.09.09 outlines the Level 1 review procedure for small generator facilities seeking to interconnect with the utility grid. This guide specifies the statutory limitations and requirements for such interconnections, ensuring safety and reliability. It applies to eligible small generator facilities evaluated under net system capacity screens, with radial circuit aggregated generation capped at 15 percent of annual peak load and shared secondary generation capped at 20 kW (August 2026).

What are the key statutory limitations for Level 1 interconnection?

Maryland's COMAR 20.50.09.09 sets several critical limitations for Level 1 small generator interconnections. These include screens for radial circuit peak load, spot network generation, shared secondary line capacity, and transformer imbalance.

The table below details these provisions:

| 20 Percent Transformer Imbalance Screen | Its addition may not create an imbalance between the two sides of the 240 volt service of more than 20 percent of the nameplate rating of the service transformer (August 2026). | Figures as of August 2026.

What are the timelines for the Level 1 interconnection process?

The COMAR 20.50.09.09 guide establishes specific timelines for utilities to process Level 1 interconnection requests. These timelines ensure a predictable and efficient review process for applicants.

| 30 Calendar Days Execution Window | If an applicant does not sign the interconnection agreement within 30 calendar days after receipt from the utility, the interconnection request is considered withdrawn (August 2026). | Figures as of August 2026.

How do utilities perform technical evaluations for Level 1 facilities?

Utilities in Maryland may use specific technical standards for evaluating Level 1 interconnection requests. COMAR 20.50.09.09 allows for the use of modern modeling methods. Specifically, a utility may use a power-flow based analysis system with modeling of IEEE 1547-2018 inverter capabilities (August 2026). This ensures that the interconnection adheres to current industry standards for safety and grid stability.

How we verified these Maryland PSC interconnection details

We verified the information presented in this guide by directly consulting the official Maryland Public Service Commission (PSC) COMAR 20.50.09.09 regulations, specifically "Md. Code Regs. 20.50.09.09 - Level 1 Review." Our review was conducted on August 23, 2026, using the publicly accessible legal database at Cornell Law School. Every figure and specific requirement cited in this article is directly sourced from this regulatory document.

Navigating Maryland's solar regulations

Understanding the specific interconnection rules is one part of installing a solar energy system in Maryland. You also need to be aware of net metering policies and how they impact your system's financial viability. For more information on how generated electricity is credited, you can refer to our guide on Maryland PSC COMAR 20.50.10.01 Solar Net Metering.

Comparing Maryland's regulations to those in neighboring states can also provide context for your project. For example, you might review the Pennsylvania PUC Level 1 Interconnection Guide or the Ohio PUCO Level 1 Interconnection Guide. These guides can help you understand regional differences in interconnection requirements.

When planning your system, accurately sizing your solar array and battery storage is crucial. You can use a solar sizing tool to estimate your energy needs and determine the appropriate system components. This will help ensure your system meets both your energy demands and the regulatory requirements.