Illinois EV Charging Electrical Terminology Glossary
Electric vehicle charging infrastructure depends on a precise shared vocabulary to ensure safe installation, code compliance, and interoperability across equipment, contractors, utilities, and inspection authorities in Illinois. This page defines the core electrical terms used throughout EV charger planning, permitting, and installation — from basic circuit concepts to utility interconnection language. Mastery of this terminology is foundational to navigating the Illinois EV Charger Authority's resource library and communicating accurately with licensed electricians, local jurisdictions, and the Illinois Commerce Commission.
Definition and scope
Scope of this glossary: The definitions on this page apply to EV charging electrical installations within the State of Illinois, governed by the Illinois Electric Vehicle Act (Public Act 102-0149), the Illinois Department of Financial and Professional Regulation (IDFPR) licensing framework for electrical contractors, and locally adopted editions of the National Electrical Code (NEC). Illinois municipalities generally adopt the NEC on a rolling cycle, with the 2020 NEC in effect in the City of Chicago and the 2023 NEC adopted by a growing number of downstate jurisdictions as of their most recent amendment cycles. This glossary does not cover federal motor vehicle safety standards, EV battery chemistry, charging network software protocols (such as OCPP), or electrical codes in neighboring states. Cross-border or federally funded installations may involve FHWA NEVI program requirements that fall outside this page's coverage.
EVSE (Electric Vehicle Supply Equipment): The NEC's umbrella term, defined in NEC Article 625, for the conductors, including the ungrounded, grounded, and equipment grounding conductors, and the electric vehicle connectors, attachment plugs, and all other fittings, devices, power outlets, or apparatus installed specifically for delivering energy from premises wiring to an EV. Understanding EVSE scope is central to NEC Article 625 compliance in Illinois.
Level 1 Charging: AC charging at 120 V, 15 A or 20 A, delivering approximately 1.2–1.9 kW. Requires a standard NEMA 5-15 or NEMA 5-20 outlet. A typical passenger EV gains roughly 3–5 miles of range per hour at Level 1.
Level 2 Charging: AC charging at 208 V or 240 V, on circuits rated from 20 A to 100 A. Output ranges from approximately 3.3 kW to 19.2 kW depending on the EVSE's maximum amperage and the vehicle's onboard charger limit. Requires a dedicated branch circuit and a NEMA 14-50, NEMA 6-50, or hardwired connection. Detailed wiring distinctions are covered on the Level 1 vs. Level 2 EV charger wiring Illinois reference page.
DC Fast Charging (DCFC): Direct-current charging that bypasses the vehicle's onboard charger, delivering power directly to the battery. Commercial DCFC units operate at 480 V three-phase and range from 50 kW to 350 kW. Illinois NEVI-funded corridor installations are required to provide a minimum of 150 kW per port (FHWA NEVI Formula Program Guidance, 2023).
Dedicated Circuit: A branch circuit reserved exclusively for a single EVSE load. NEC 625.40 requires that EV charging equipment be supplied by a dedicated branch circuit; no additional outlets or loads may share this circuit. Illinois-specific requirements are outlined at dedicated circuit requirements for EV charging Illinois.
Branch Circuit: The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s). For EV charging, the overcurrent device is typically a circuit breaker in the service panel sized at 125% of the continuous load per NEC 210.20(A). Breaker sizing for EV charging in Illinois addresses local application of this rule.
Service Entrance: The point at which utility-supplied conductors enter the premises and connect to the meter base and main disconnect. Upgrading from a 100 A to a 200 A or 400 A service entrance is frequently required for multi-unit or commercial EV charging projects. See EV charging electrical service entrance requirements Illinois for a full breakdown.
Load Calculation: The engineering process defined in NEC Article 220 for determining the total connected and demand load on a service or feeder. EV chargers are treated as continuous loads, meaning 125% of the nameplate amperage is added to the load calculation. Load management for EV charging in Illinois covers demand response strategies that can reduce calculated load.
Ampacity: The maximum current, in amperes, that a conductor can carry continuously under defined conditions without exceeding its temperature rating. Conductor ampacity tables appear in NEC Article 310. Wire gauge selection for EV chargers in Illinois translates ampacity tables into practical recommendations.
Voltage Drop: The reduction in voltage along a conductor due to its resistance. NEC informational notes recommend limiting voltage drop to 3% on branch circuits and 5% total on combined feeders and branch circuits. Longer conduit runs in large parking structures make voltage drop a critical design variable.
Grounding and Bonding: Two related but distinct concepts. Grounding connects the electrical system to earth to limit voltage during faults. Bonding connects metallic components together to ensure a low-impedance fault-current path. NEC Article 250 governs both; EV-specific grounding requirements appear in NEC 625.54. A dedicated reference on EV charger grounding and bonding in Illinois provides application detail.
GFCI (Ground Fault Circuit Interrupter): A device that interrupts the circuit within 25 milliseconds when it detects a current imbalance of 4–6 milliamperes between the ungrounded and grounded conductors, indicating current leakage to ground. NEC 625.54 requires GFCI protection for all EVSE outlets in dwelling unit garages and other defined locations. Ground fault protection for EV charging in Illinois details where GFCI is mandatory versus optional.
Conduit Fill: The ratio of conductor cross-sectional area to interior conduit area, regulated by NEC Chapter 9. Maximum fill is 40% for three or more conductors in a single conduit run. Correct conduit fill is verified at inspection. EV charger conduit and wiring methods in Illinois covers conduit type selection (EMT, PVC, RMC) under Illinois field conditions.
Demand Charge: A utility billing component based on the peak kilowatt draw during a billing interval, typically 15 or 30 minutes, rather than total energy consumed. Illinois utilities regulated by the Illinois Commerce Commission impose demand charges on commercial accounts; unmanaged EV charging can significantly increase peak demand. Demand charge management for EV charging in Illinois addresses mitigation strategies.
Smart Charging / Load Management: The use of communication-enabled EVSE and energy management systems to schedule, throttle, or shed EV charging loads in response to grid signals, time-of-use rates, or on-site demand limits. Illinois utilities including ComEd offer demand response programs compatible with smart EVSE. Smart panel integration for EV chargers in Illinois covers panel-level coordination.
EV-Ready Wiring: A construction practice in which conduit, wiring, and a circuit breaker space are installed during initial construction to enable future EVSE installation without structural work. Illinois's EV Ready Law (Public Act 101-0595) mandates EV-ready parking spaces in new construction above specified thresholds. EV-ready wiring for new construction in Illinois provides the statutory thresholds and technical specifications.
Panel Upgrade / Service Upgrade: The replacement of an existing electrical panel or service entrance equipment with one of greater ampacity. Triggers a permit and inspection under local jurisdictional authority and, where applicable, requires coordination with ComEd or other serving utilities for meter base clearance. Electrical panel upgrades for EV charging in Illinois covers the process in detail.
How it works
EV charging terminology functions as a layered classification system, with each term mapping to a specific section of the NEC, an inspection checkpoint, or a utility tariff concept. The conceptual overview of Illinois electrical systems explains how these layers interact. The practical flow from source to vehicle follows five discrete stages:
- Utility service delivery — The serving utility (ComEd, Ameren Illinois, MidAmerican Energy, or one of Illinois's 25 municipal utilities) delivers AC power at the service entrance voltage (120/240 V single-phase for residential; 120/208 V or 277/480 V three-phase for commercial).
- Metering and main disconnect — The kilowatt-hour meter and main breaker establish the boundary between utility and customer equipment.
- Distribution panel — The load center distributes power to individual branch circuits via circuit breakers. Panel