EV Charger Metering and Submetering in Maryland

Metering and submetering for EV chargers determine how electricity consumption at charging stations is measured, allocated, and billed — a question that has grown more pressing as Maryland expands its EV charging infrastructure under programs administered by the Maryland Energy Administration and the Public Service Commission. This page covers the definition of EV charger metering and submetering, the technical and regulatory mechanisms that govern them, the scenarios where each approach applies, and the decision factors that distinguish one configuration from another. Understanding these distinctions is essential for residential, commercial, and multi-unit property owners navigating Maryland's electrical and utility frameworks.

Definition and scope

Metering, in the context of EV charging, refers to the measurement of electrical energy delivered through a charging circuit, typically recorded in kilowatt-hours (kWh). A dedicated meter is a standalone utility-grade instrument installed by or in coordination with the serving utility — in Maryland, primarily Baltimore Gas and Electric (BGE), Pepco, Delmarva Power, or Potomac Edison — to measure consumption at a specific service point.

Submetering is distinct: a submeter sits behind the primary utility meter on a property's internal electrical system, measuring energy consumption at a subset of the total load. Submeters do not replace the utility meter; they subdivide measurements within a building or campus. For EV charging, a submeter on a Level 2 charging circuit allows a property owner to track exactly how many kWh are consumed by vehicle charging — separate from lighting, HVAC, or other loads.

Maryland's regulatory scope for submetering involves overlapping authority. The Maryland Public Service Commission (PSC) regulates retail electricity sales and has issued guidance affecting submetering at multi-unit dwellings. The Maryland Department of Labor's Electrical Division enforces the Maryland Electrical Code, which adopts the National Electrical Code (NEC) and governs the installation standards for metering equipment.

Scope and limitations: This page addresses Maryland-specific regulatory and installation considerations. It does not cover federal metering requirements imposed by the Federal Energy Regulatory Commission (FERC) on wholesale transactions, nor does it address submetering in states other than Maryland. Utility tariff specifics vary by service territory and are not exhaustively catalogued here.

How it works

EV charger metering and submetering operate within Maryland's electrical infrastructure as described in the conceptual overview of Maryland electrical systems. The measurement chain typically flows as follows:

1. Utility revenue meter — Installed and owned by the serving utility at the service entrance. Records total site consumption billed to the account holder.
2. Subpanel or dedicated branch circuit — A circuit rated at 240V/50A (for a typical Level 2 EVSE) or higher runs from the main panel or a subpanel to the charging equipment. See dedicated circuit requirements for EV charging in Maryland for branch circuit sizing standards.
3. Submeter device — A revenue-grade or sub-revenue-grade interval meter is installed on the dedicated EV circuit, upstream of the EVSE. Revenue-grade meters must meet ANSI C12.1 accuracy standards (typically ±0.5% or better). Sub-revenue-grade meters, used for internal cost allocation rather than tenant billing, have wider tolerance bands.
4. Data output — Modern submeters transmit consumption data via Modbus, BACnet, or cloud-connected protocols to an energy management system or building automation platform.
5. Billing or allocation — Data feeds reimbursement calculations for fleet operators, tenant billing in commercial properties, or workplace charging cost recovery.

For DC fast chargers, which may draw 50 kW to 350 kW per port, a dedicated utility meter is often the practical choice rather than a submeter, as the load magnitude justifies a separate service point. The Maryland utility interconnection process for EV charging outlines how separate service applications are filed with the distribution utility.

NEC Article 625 governs EVSE installation broadly, and NEC Article 230 and Article 250 address service entrance and grounding requirements that affect where metering equipment can be legally placed. These requirements are set forth in NFPA 70, 2023 edition (effective 2023-01-01). Maryland electrical permits — issued by local Authority Having Jurisdiction (AHJ) offices — are required for new metering and submetering installations. The permit process is addressed in the regulatory context for Maryland electrical systems.

Common scenarios

Residential single-family: A homeowner installs a 48A Level 2 charger and wants to track charging costs separately from household consumption. A submeter on the dedicated 60A circuit provides kWh data for utility rebate verification or time-of-use rate analysis. BGE's EV pricing riders, for example, require interval data to confirm off-peak charging.

Multi-unit dwellings (MUDs): Maryland law under Md. Code, Public Utilities Article §7-306 permits submetering in multi-unit buildings subject to PSC approval and rate-cap protections for tenants. A submetered EV parking stall allows the property owner to bill residents for actual charging consumption without requiring each resident to establish an individual utility account. The multi-unit dwelling EV charger electrical systems page addresses the full installation context.

Workplace charging: Employers offering EV charging as a benefit often submeter charging stations to calculate the taxable value of the benefit or to allocate costs to departments or vehicle fleets. See workplace EV charging electrical considerations in Maryland.

Commercial public charging: A retail property deploying networked Level 2 or DC fast chargers for public use will typically obtain a separate utility meter per charging installation, especially if the charger operator is distinct from the property's general electricity account holder.

Fleet depots: Fleet operators managing 10 or more vehicles at a single site frequently deploy smart load management systems alongside submetering to prevent demand charge spikes. The fleet EV charging electrical infrastructure page covers load orchestration in this context.

Decision boundaries

Choosing between a dedicated utility meter and a submeter involves regulatory, financial, and operational factors:

The smart load management page for Maryland EV chargers details how submetering integrates with demand response and load control systems, which affect Maryland electrical panel capacity for EV charging.

A broader orientation to the regulatory framework governing metering decisions is available at the Maryland EV charger authority index. For older properties where panel capacity constrains submetering options, the electrical system upgrades for older homes in Maryland page addresses retrofit pathways.

Parking structures present unique submetering challenges due to the number of stalls and the shared electrical infrastructure. The parking garage EV charger electrical systems page covers distribution architecture relevant to metering decisions in those environments.

References

• Maryland Public Service Commission (PSC)
• Maryland Department of Labor – Electrical Division
• Maryland Energy Administration
• Maryland Code, Public Utilities Article §7-306 – Submetering
• National Electrical Code (NEC) – NFPA 70, 2023 Edition, Article 625 (Electric Vehicle Power Transfer System)
• ANSI C12.1 – Electric Meters Code for Electricity Metering (American National Standards Institute)
• Baltimore Gas and Electric (BGE) – EV Resources
• Federal Energy Regulatory Commission (FERC) – Metering Overview