Maryland Utility Interconnection Concepts for EV Charging

Utility interconnection governs how an EV charging installation connects to the electrical grid and, in Maryland, determines which technical standards, utility tariffs, and regulatory approvals apply before equipment can operate. This page covers the definition of interconnection in the context of EV charging, the procedural steps involved, common installation scenarios, and the boundaries that separate different regulatory pathways. Understanding these concepts is foundational to any compliant installation, from a single-family Level 2 charger to a commercial DC fast charging station.

Definition and scope

In the electrical utility context, interconnection refers to the formal process by which a customer-owned load or generation system is physically and electrically joined to a utility's distribution network. For EV charging, the term primarily concerns the service entrance upgrade, metering configuration, and load addition notification requirements that utilities in Maryland impose on new or expanded charging installations.

Maryland's two largest investor-owned utilities — Baltimore Gas and Electric (BGE) and Pepco — each publish interconnection and service extension guidelines that establish how new electrical loads, including EV charging equipment, must be evaluated and approved (Maryland Public Service Commission). The Maryland Public Service Commission (PSC) regulates these utilities under Maryland Code, Public Utilities Article, and oversees tariff filings that define the technical and commercial terms of grid connection.

Interconnection for EV charging is distinct from the interconnection of distributed generation (such as solar PV or battery storage). A pure charging load does not export power to the grid under standard operation, so it falls under the utility's load addition and service upgrade procedures rather than the full distributed generation interconnection process. However, when solar integration with EV charger electrical systems or battery storage EV charger electrical systems are present, the regulatory pathway shifts and additional interconnection rules apply.

Scope and coverage limitations: This page addresses interconnection concepts as they apply within Maryland, under the jurisdiction of the Maryland PSC and the tariffs of Maryland-regulated utilities. It does not cover interstate transmission-level interconnection, federal FERC interconnection orders, or installations in municipalities served by municipal utilities that operate outside PSC jurisdiction. Washington Gas, which serves portions of Maryland, is regulated separately from electric utilities and is not covered here.

How it works

The interconnection process for an EV charging load addition proceeds through a structured sequence of steps governed by the applicable utility's tariff and the Maryland PSC's service rules.

1. Load assessment — The installer or property owner determines the new electrical demand the charging equipment will add, expressed in kilowatts (kW). A Level 2 charger typically adds 7.2–19.2 kW; a DC fast charger can add 50–350 kW or more. This feeds directly into Maryland EV charger load calculation concepts.
2. Service evaluation request — The utility receives a formal request to evaluate whether the existing service entrance and distribution transformer can support the new load. BGE and Pepco publish specific forms for this purpose through their customer portals.
3. Transformer and feeder capacity review — The utility's engineering team checks whether the local transformer serving the premises has sufficient capacity. If the transformer is undersized, the utility schedules an upgrade, which may involve cost-sharing under the utility's extension tariff.
4. Metering configuration — The utility determines whether existing metering is adequate. Some EV-specific tariff riders (BGE's EV rate schedules, for example) require a dedicated meter or sub-meter. EV charger metering and submetering in Maryland details those requirements.
5. Service agreement execution — A written agreement between the customer and utility formalizes the terms, including any contribution in aid of construction.
6. Inspection and energization — After local inspection authority approval (county or municipal electrical inspector), the utility energizes the upgraded service.

The National Electrical Code (NEC), NFPA 70 2023 edition, adopted in Maryland through the Maryland Building Performance Standards, governs the wiring methods and equipment standards on the customer side of the meter. The utility governs everything up to and including the meter. The point of demarcation between these two domains is the service entrance, discussed further in the conceptual overview of Maryland electrical systems.

Common scenarios

Residential Level 2 addition: A homeowner adding a 240 V, 48 A Level 2 charger may trigger a service upgrade if the existing 100 A panel is already near capacity. The Maryland electrical panel capacity for EV charging framework applies, and the utility must be notified if the service entrance ampacity changes. BGE's residential service tariff (Schedule R) and associated EV riders govern the rate treatment.

Commercial multi-port installation: A retail property installing 4 Level 2 charging ports (each at 7.2 kW) adds approximately 28.8 kW of potential load. The utility's service extension process is nearly always triggered. Commercial EV charger electrical installation in Maryland addresses the permitting side of this scenario.

DC fast charger at a fleet depot: A 150 kW DC fast charger at a fleet facility requires coordination with the utility well in advance of installation — often 6 to 18 months — due to transformer and feeder upgrade lead times. Fleet EV charging electrical infrastructure in Maryland covers the infrastructure planning elements.

Multi-unit dwelling (MUD): Apartment and condominium installations involve shared service entrances and may require sub-metering to allocate costs per resident. The PSC has issued guidance on MUD EV charging under its electric vehicle proceeding. Multi-unit dwelling EV charger electrical systems in Maryland addresses the specific electrical architecture.

Decision boundaries

The critical decision boundary in Maryland interconnection is whether the proposed EV charging load requires a new or upgraded service entrance versus a simple panel-level circuit addition within an existing service.

A secondary boundary separates investor-owned utility (IOU) territory from cooperative and municipal utility territory. Choptank Electric Cooperative and SMECO (Southern Maryland Electric Cooperative) follow interconnection guidelines developed under NRECA standards and are not governed by the same PSC tariff schedules as BGE or Pepco. Installations in their service areas must consult those cooperatives directly.

The regulatory context for Maryland electrical systems page provides additional framing on how the PSC, local inspection authorities, and the NEC interact across the full permitting and approval chain. For a site-by-site overview of all relevant electrical concepts for EV charging in Maryland, the Maryland EV Charger Authority home is the entry point to the full topic set.

References

• Maryland Public Service Commission (PSC) — Regulates investor-owned utilities in Maryland; publishes tariff filings, EV proceeding orders, and service rules
• Baltimore Gas and Electric (BGE) Tariff Schedules — Residential and commercial rate schedules including EV riders
• Pepco Maryland Tariff Information — Pepco tariff filings for Maryland service territory
• National Electrical Code (NEC), NFPA 70, 2023 edition — Governs customer-side wiring standards adopted in Maryland
• Maryland Building Performance Standards, Maryland Department of Labor — Establishes NEC adoption status in Maryland
• Choptank Electric Cooperative — Maryland electric cooperative with independent interconnection guidelines
• SMECO (Southern Maryland Electric Cooperative) — Maryland electric cooperative serving Southern Maryland counties
• National Rural Electric Cooperative Association (NRECA) — Standards body for cooperative utility interconnection guidelines