Program Interconnection Standards
Category Regulatory Policy
Implementing sector State
Last Update
State Maryland
Technologies Solar Thermal Electric, Solar Photovoltaics
Sectors Residential

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 20 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. 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.

Maryland undertook a rulemaking (RM61) in December 2017 to implement recommendations from 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 other improvements. The new regulations added energy storage to interconnection procedures and made amendments to interconnection process for systems larger than 25 kW and 2 MW, along with other minor changes.

As of January 1, 2024, in Maryland, any small generator facility requiring an inverter for which an interconnection is submitted shall use a smart inverter that meets the requirements of IEEE Standard 1547-2018 and UL Standard 1741-SB, or subsequent revisions to these standards. In addition, all newly interconnected smart inverters are required to use Maryland’s state-wide standard settings profile, a utility specific default profile (DU-URP), or a utility site-specific (IA-URP) settings profile which are based on the Hierarchy of Distributed Energy Resource Interconnection Requirements & Settings established by the Electric Power Research Institute (EPRI).

*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.

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