Interconnection Standards

January 26, 2018


NOTE: In December 2017, the Maryland Public Service Commission initiated rulemaking docket (RM61) to consider revisions to the small generation interconnection process as recommended by stakeholders of the Public Conference 44 Interconnection Working Group. The working group reached consensus on making interconnection process more efficient, allowing applications to be filed electronically, removing monitoring for systems less than 2MW, and others improvements. The proposed regulations include i) addition of energy storage for interconnection, ii) amendments to interconnection process for systems larger than 25 kW and 2 MW, and a number of other minor changes. 

In April 2007, Maryland enacted legislation (S.B. 595) requiring the Maryland Public Service Commission (PSC) to form a small generator interconnection working group to develop interconnection standards and procedures that are "consistent with nationally adopted interconnection standards and procedures," and to revise the state's interconnection standards and procedures on or before November 1, 2007. Final rules were adopted in March 2008 and became effective June 9, 2008.

The new rules apply to interconnections of all types of distributed generation systems of less than 10 MW to the electric distribution system for all types of utilities -- investor-owned utilities, rural cooperatives and municipal utilities. Interconnections that are subject to PJM Interconnection are exempt from this rule.

Standard Interconnection agreement employs a four-tiered approach to determine the level of review required before a system may be connected to the grid. Different levels of review are subject to specific technical screens, review procedures, and time lines. Generally speaking, the review process becomes more extensive and time consuming with increasing system size. Below are the basic criteria* for determining the level of review required for a prospective project.

  • Level 1: Lab certified, inverter-based systems of 10 kW or less.
  • Level 2: Lab certified or field approved systems of 2 MW or less connected to a radial distribution circuit or to a spot network serving one customer.
  • Level 3: Only applies to systems that will not export power to the grid and which do not require new facility construction by the utility. Systems being located on an area network must be inverter-based, use lab certified equipment, and have a capacity of 50 kW or less. Systems located on a radial network must have a capacity of 10 MW or less and not be served by a shared transformer. These systems are also subject to additional criteria dealing with the aggregate capacity of interconnected systems on a given network.
  • Level 4: Systems 10 MW or less that cannot be approved or do not meet the criteria for review under a lower tier.

Lab certified equipment is defined to mean equipment tested and approved by a nationally recognized testing laboratory (NRTL) as being in accordance with IEEE 1547, UL 1741, and the National Electric Code (NEC). Field approved systems are generally non-certified systems that have been tested and approved under a prior review by a utility, subject to certain other restrictions. All interconnected systems must be equipped with a utility accessible “lockable isolation device” or alternately, a “draw-out type circuit breaker with a provision for padlocking at the draw-out position”. This requirement is equivalent to “lockable external disconnect switch” frequently specified in other jurisdictions.

Utilities may not charge any processing fees to Level 1 applicants and processing fees are limited to $50 plus $1/kilowatt (kW) of capacity for Level 2 requests and $100 plus $2/kW of capacity for Level 3 and 4 requests. Utilities are also required to designate a contact person and provide assistance materials on their website for use by prospective applicants. Standardized interconnection agreements are available on the PSC renewable portfolio standard website for all levels of interconnection request. The regulations also contain provisions for dispute resolution and utility reporting requirements.

The issue of insurance additional insurance requirements is not addressed by the regulations. However, the standard Level 1 interconnection agreement specifically states that applicants are not required to obtain general liability insurance as a condition of interconnection approval. For Levels 2, 3 and 4 the interconnection agreement requires liability insurance of at least $2 million per occurrence and $4 million in aggregate for systems of 1 MW or larger. It also specifies that the policy must name the utility as an additional insured party. A separate standard agreement exists for Maryland state and local government entities, which among other things contains modifications to liability insurance requirements that accommodate self-insured entities.

*The general descriptions here are not a comprehensive listing of all testing and review criteria. Please see the actual rules for more details and additional restrictions that may apply.

Program Overview

Implementing Sector: State
Category: Regulatory Policy
State: Maryland
Incentive Type: Interconnection
Web Site:
Start Date:
Eligible Renewable/Other Technologies:
  • Geothermal Electric
  • Solar Thermal Electric
  • Solar Photovoltaics
  • Wind (All)
  • Biomass
  • Combined Heat & Power
  • Fuel Cells using Non-Renewable Fuels
  • Landfill Gas
  • Tidal
  • Wave
  • Ocean Thermal
  • Wind (Small)
  • Anaerobic Digestion
  • Fuel Cells using Renewable Fuels
  • Other Distributed Generation Technologies
Applicable Utilities: All utilities
System Capacity Limit: 10 MW
Standard Agreement: Yes
Insurance Requirements: Vary by system size and/or type; levels established by PSC
External Disconnect Switch: Required
Net Metering Required: No


Name: COMAR 20.50.09 Small Generator Interconnection Standards
Date Enacted: 03/25/2008
Effective Date: 06/09/2008


Name: Ude l. Ude
Organization: Maryland Public Service Commission
Address: 6 St. Paul Street
Baltimore MD 21202
Phone: (410) 767-8510

This information is sourced from DSIRE; the most comprehensive source of information on incentives and policies that support renewables and energy efficiency in the United States. Established in 1995, DSIRE is operated by the N.C. Clean Energy Technology Center at N.C. State University.