Electrical Metering for EV Charging Stations in Missouri
Electrical metering for EV charging stations determines how electricity consumption is measured, billed, and reported at charge points — a function that affects utility cost allocation, rate structure eligibility, and compliance with Missouri Public Service Commission requirements. This page covers the primary metering configurations used in Missouri, the technical and regulatory distinctions between them, and the decision factors that govern meter placement and type selection. Understanding these distinctions matters because metering choices made at the design stage directly affect long-term operating costs, utility interconnection timelines, and the feasibility of submetering in multi-tenant environments.
Definition and scope
Electrical metering, in the context of EV charging infrastructure, refers to the hardware, firmware, and utility-tariff framework used to measure kilowatt-hours (kWh) delivered to one or more charging units. A meter may be utility-owned and installed at the service entrance, or it may be a privately owned submeter installed downstream to allocate costs among multiple users or tenants.
In Missouri, electric utility service — and the metering associated with it — falls under the jurisdiction of the Missouri Public Service Commission (MPSC). The MPSC regulates investor-owned utilities including Ameren Missouri and Evergy, setting tariff schedules and metering standards that govern how EV charging loads are accounted for. Cooperatives and municipal utilities operate under separate governance structures and are generally not subject to MPSC rate regulation, though they follow National Electrical Code (NEC) installation standards.
National Electrical Code Article 625 addresses electric vehicle power transfer systems, and NEC Article 230 governs service entrances where utility meters are typically located. Missouri adopts the NEC through the Missouri Division of Fire Safety, which administers the state electrical code, though local jurisdictions may adopt amendments. The current adopted edition is NFPA 70: National Electrical Code, 2023 edition (effective 2023-01-01). For a broader orientation to how Missouri electrical systems are structured and regulated, see Missouri Electrical Systems: Conceptual Overview.
Scope limitations: This page addresses metering concepts applicable to Missouri's investor-owned utility service territories and properties subject to the state electrical code. It does not cover federal metering requirements for commercial fleet operations under DOE or FERC jurisdiction, metering rules specific to cooperative or municipal utility customers (which vary by provider), or billing software platforms. Charger network communication protocols such as OCPP fall outside this scope.
How it works
Utility-grade metering at an EV charging site follows a structured sequence:
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Service entrance metering — The utility installs a revenue-grade meter at the point of delivery, typically on the meter base at the main service entrance. This meter records total site consumption and is used for utility billing. In Missouri, Ameren Missouri and Evergy each publish metering specifications and approved meter bases in their tariff filings with the MPSC.
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Load identification — For sites where EV charging represents a significant fraction of total load, utilities may require load studies or load calculations to verify that the existing service can accommodate additional demand without violating voltage drop or capacity thresholds.
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Submeter installation (where applicable) — A privately owned submeter is installed downstream of the utility meter to isolate EV charging consumption from general building load. Submeters must meet ANSI C12.1 accuracy standards (published by the American National Standards Institute) if used for cost allocation or tenant billing. Missouri does not have a state-level submetering statute specifically governing EV applications, so contractual arrangements and landlord-tenant law govern billing disputes.
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Tariff enrollment — Depending on meter configuration and demand level, the site operator may qualify — or be required — to enroll in a time-of-use (TOU) or demand-charge rate schedule. Ameren Missouri's Schedule EV and comparable Evergy EV rate options apply specific metering requirements tied to charger type and rated output.
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Inspection and approval — Meter base installations and any wiring to meter sockets require inspection by the authority having jurisdiction (AHJ), consistent with permitting and inspection concepts applicable to Missouri electrical projects.
Common scenarios
Single-family residential (Level 2): A homeowner installs a 240V, 48-ampere Level 2 EVSE on an existing utility account. No separate meter is required; consumption is captured on the existing residential meter. The utility may offer a special EV rate requiring a second meter socket for time-differentiated billing — a configuration sometimes called a "dual meter" or "EV rider" setup.
Commercial site with dedicated EV service: A retail property installs a DC fast charger rated at 50 kW or higher. Because this load is large enough to trigger demand charges, the utility typically requires a dedicated service entrance with its own revenue meter, separate from the building's primary account. This arrangement simplifies billing and avoids demand-charge blending with the building's base load. See DC Fast Charger Electrical Infrastructure in Missouri for infrastructure context.
Multi-unit dwelling (MUD): An apartment complex installs 12 Level 2 chargers across a parking structure. The building owner uses ANSI C12.1-compliant submeters at each charger to bill tenants for actual consumption. Missouri's multi-unit environment presents specific challenges covered in Multi-Unit Dwelling EV Charging Electrical.
Workplace charging with cost recovery: An employer installs chargers and recovers costs from employees. Submetering with session-level data output (often via OCPP-compatible EVSE) allows reconciliation between metered kWh and billing records without triggering utility resale regulations, provided the employer does not mark up the electricity rate above utility cost — a distinction that touches Missouri's definition of a "public utility" under RSMo Chapter 386.
Decision boundaries
The choice of metering configuration depends on four primary variables:
| Factor | Separate Utility Meter | Submeter Only | Dual-Meter (EV Rider) |
|---|---|---|---|
| Load size | >50 kW demand | <50 kW, shared site | Residential or small commercial |
| Tenant billing needed | Not primary driver | Required | Not typically applicable |
| Utility rate optimization | Demand-charge isolation | Not applicable | TOU rate access |
| Installation cost | Higher (service upgrade likely) | Lower | Moderate |
A dedicated utility meter for EV service isolates the charger load from other building loads, preventing EV demand peaks from inflating demand charges on the building account. This separation is often justified for commercial EV charging electrical design at sites with 100 kW or more of aggregate charger capacity.
Submetering alone — without a dedicated utility service — is appropriate when aggregate EV load remains a small fraction of total site demand and the primary goal is internal cost allocation rather than rate optimization. Smart load management systems can be paired with submeters to cap EV demand within a pre-set threshold, reducing the risk of triggering demand-charge ratchet clauses.
The Missouri regulatory context for these determinations, including how utility tariff structures interact with metering requirements, is addressed in detail at Regulatory Context for Missouri Electrical Systems. The broader Missouri EV Charger Authority home provides orientation across all EV charging infrastructure topics covered in this resource.
For projects where network-connected EV charger electrical considerations are in scope, metering data output and session reporting functions must be evaluated alongside physical meter placement to ensure data integrity and compatibility with utility demand-response programs.
References
- Missouri Public Service Commission (MPSC) — Regulatory authority over investor-owned electric utilities in Missouri; tariff filings and metering standards.
- Missouri Division of Fire Safety — Electrical Program — State authority for electrical code adoption and enforcement in Missouri.
- NFPA 70: National Electrical Code, 2023 Edition, Article 625 (Electric Vehicle Power Transfer Systems) — Installation requirements for EVSE wiring and metering integration. Current edition effective 2023-01-01.
- ANSI C12.1 — American National Standard for Electric Meters: Code for Electricity Metering — Accuracy and performance standards for revenue-grade and submetering equipment.
- Missouri Revised Statutes Chapter 386 — Public Service Commission Law — Statutory definition of "public utility" relevant to resale and cost-recovery billing structures.
- Ameren Missouri Tariff Schedules (MPSC Electric Tariff) — Rate schedules including EV-specific metering and service options.
- Evergy Missouri Tariff Information — Tariff schedules applicable to Evergy service territory EV customers.