NEC Article 625: EV Charging Installations

Electric vehicle charging installations are now part of every residential service upgrade quote and a large fraction of commercial new construction. Article 625 has expanded significantly across the 2017, 2020, and 2023 NEC cycles and is one of the most frequently tested topics on current journeyman and master exams.

This guide covers every section of Article 625 that commonly appears on licensing exams, with worked examples for branch circuit sizing and a quick reference table for exam day.

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Article 625 Structure

Article 625 is organized into seven parts:

• Part I, General (625.1 through 625.6)
• Part II, Equipment Construction (625.10 through 625.30)
• Part III, Installation (625.40 through 625.60)
• Part IV, Wireless Power Transfer Equipment (625.101 through 625.103)
• Part V, Interactive Systems (625.48)
• Part VI, DC Supply Equipment (625.50)
• Part VII, Special Locations

Exam questions are concentrated in Part III, the installation rules.

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Key Definitions, 625.2

A few definitions matter for exam questions:

• Electric Vehicle Supply Equipment (EVSE): The conductors, attachment plug, ungrounded conductors, grounded conductors, and equipment grounding conductor located between the premises wiring and the electric vehicle for charging the vehicle.
• Output Cable: The flexible cord between the EVSE and the electric vehicle.
• Personnel Protection System: A listed system of safety features that prevent electric shock during charging operations.

EVSE is not a charger. The actual charger is on board the vehicle. The EVSE on the wall is a safety controlled supply with communication and protection.

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Part III: Installation Requirements

625.40, Individual Branch Circuit

Each EVSE outlet must be supplied by an individual branch circuit.

No other loads can share the circuit. This is the rule violated by the most common garage retrofit, hooking an EV charger into a NEMA 14 50 dryer outlet wired to a 30 amp breaker.

625.41, Overcurrent Protection (Continuous Load Rule)

EVSE is a continuous load. The branch circuit overcurrent device and conductors must be sized at not less than 125 percent of the maximum load.

The math:

Branch circuit OCPD = EVSE rated load × 1.25 Conductor ampacity = EVSE rated load × 1.25

This is the same continuous load rule used throughout the NEC. The 125 percent factor protects breakers and conductors from running at 100 percent of their rating for hours during a charging session.

625.42, EVSE Rating

EVSE has a continuous rating that shall not exceed 80 percent of the branch circuit rating.

This is the inverse of the 625.41 rule, written from the perspective of the EVSE selection rather than the circuit sizing.

Practical lookup:

This is why most commonly installed Level 2 home chargers are rated 32, 40, or 48 amperes. Those values cleanly match 40, 50, and 60 ampere branch circuits.

625.43, Disconnecting Means

A disconnecting means is required for EVSE rated more than 60 amperes or more than 150 volts to ground.

The disconnect must be:

• Readily accessible
• Lockable in the open position
• Installed in a location separate from the EVSE in some cases, depending on the listing

For EVSE rated 60 amperes or less and 150 volts to ground or less, the branch circuit overcurrent device can serve as the disconnect, provided it is within sight of the EVSE or lockable in the open position.

625.46, Loss of Primary Source

EVSE must de energize the output cable when the primary source is removed.

This prevents back feed into a de energized service during utility outages or work on the premises wiring.

625.48, Interactive Systems

EVSE that exports power back to the utility (vehicle to grid or V2G) is treated as an interconnected power production source. Such EVSE must comply with Article 705 in addition to Article 625.

V2G is still uncommon but is appearing in newer installations and is testable on master level exams.

625.52, Ventilation

Mechanical ventilation is required only when the vehicle requires it per its listing.

For modern lithium ion EVs (the vast majority of passenger and light truck applications), no ventilation is required. The 2014 code cycle removed the default ventilation requirement that older code books required for "all" indoor charging.

Listed lead acid traction battery vehicles, primarily some industrial forklifts, may still require ventilation per their listing.

625.54, GFCI Protection

GFCI protection for personnel is required for receptacle outlets supplying single phase EVSE rated:

• 125 V through 250 V to ground
• 50 amperes or less

Hardwired EVSE with integral ground fault sensing satisfies the requirement without a separate GFCI breaker. Look for the listing standard markings on the EVSE label.

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Worked Example: Sizing a Residential Level 2 EVSE

A homeowner wants to install a Tesla Wall Connector rated 48 amperes continuous on a single phase 240 volt service.

Step 1, Apply 625.42 (EVSE max at 80 percent of circuit):

Required branch circuit = EVSE rating / 0.80 = 48 / 0.80 = 60 amperes

Step 2, Confirm 625.41 (continuous load at 125 percent):

OCPD minimum = 48 × 1.25 = 60 amperes

The two rules cross check. A 60 ampere branch circuit is required.

Step 3, Size conductors:

At 60 amperes, using 75 degree C terminations and Table 310.16:

• 6 AWG copper THWN-2 at 75 degrees C: 65 amperes ampacity

Adjust for temperature and conduit fill as applicable. After adjustments, 6 AWG copper is the typical choice for a 60 ampere EVSE circuit.

Step 4, Disconnect requirement:

48 amperes is at or below 60 amperes, and 240 V single phase has 120 V to ground (at or below 150 V to ground). The 60 ampere breaker at the panel can serve as the disconnect provided it is lockable open or within sight.

Step 5, GFCI:

For a hardwired Tesla Wall Connector with integral ground fault detection per its listing, no separate GFCI breaker is required. If the install uses a NEMA 14 50 receptacle and cord connected EVSE, a GFCI breaker is required per 625.54.

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Multi Unit and Commercial Installations

625.60, Energy Management Systems

EVSE installations that use energy management systems (EMS) to dynamically allocate power across multiple chargers can be sized based on the maximum simultaneous load, not the sum of EVSE nameplate ratings.

This is a major design lever for multi family and commercial parking installations. A 200 ampere panel can serve eight 40 ampere EVSE units with EMS, where the EMS limits total simultaneous draw to the panel rating, rather than 8 × 50 = 400 amperes of dedicated circuits.

Load Calculations for Service Sizing

EVSE loads on a dwelling unit service load calculation are treated per Article 220:

• Standard method (220.40 series): Add 7,200 VA per EVSE outlet (30 ampere, 240 V) or the actual continuous load at 125 percent, whichever is greater.
• Optional method (220.82): Add EVSE load to the general loads at 100 percent of the first 10 kVA and 40 percent of the remainder.

The optional method commonly determines whether an existing 200 ampere service can absorb an added EV charger or whether a service upgrade is required.

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Quick Reference: Key Numbers for Exam Day

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Related Reading

• NEC Article 220: Load Calculations
• NEC Article 230: Services
• NEC Article 240: Overcurrent Protection
• GFCI and AFCI Requirements
• NEC 2023 vs 2020 Changes
• Start Your Practice Test