16.2 Energy Storage and EV Charging (Articles 706, 625)

Why Articles 706 and 625 Matter for the TX Journeyman Exam

Content-outline area 10 (Renewable Energy Technologies) extends beyond solar to include energy storage systems (ESS) and electric vehicle charging. The exam tests these primarily on the NEC Knowledge part — scope, disconnecting means, labeling, and continuous-load classification — with EVSE branch-circuit sizing also appearing on the Calculations part.

Use the 2026 edition for both equipment requirements and the separate Article 120 load calculation.

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Energy Storage Systems — Article 706

Scope (706.1)

Article 706 applies to all ESS with a capacity greater than 1 kWh (3.6 MJ) that operate stand-alone or interactive with other power sources. This covers most modern battery systems (lithium-ion, flow batteries, etc.). Stationary battery installations that are not listed energy storage systems are addressed by Article 480.

Key Provisions

ESS Disconnecting Means — 706.15 Details

706.15(B) requires the disconnect to be readily accessible and comply with one of:

1. Located within the ESS
2. Within sight and within 10 ft of the ESS
3. If not within sight, capable of being locked in the open position per 110.25

706.15(B) Emergency Shutdown (one- and two-family dwellings): must include an emergency shutdown function to cease power export, with the initiation device located readily accessible outside the building.

706.15(C) marking: must plainly indicate open/closed position and be marked "ENERGY STORAGE SYSTEM DISCONNECT." For non-dwelling installations, marking must include nominal battery voltage, available fault current, arc-flash label, and date of calculation.

ESS Grounding

ESS grounding and bonding comply with Article 250. Key applications:

• Equipment grounding conductors sized per Table 250.122 based on the OCPD rating
• Connection to the building's grounding electrode system
• Bonding jumpers between metallic ESS enclosures, racking, and conduit
• For DC battery systems with ungrounded (floating) circuits, a ground-fault detection device is essential

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Electric Vehicle Supply Equipment — Article 625

Scope (625.1)

Article 625 covers the electric vehicle charging system: the EVSE (supply equipment), the connector, and the cable between them. It applies to wired-in (fixed) and cord-and-plug-connected equipment in residential, commercial, and public locations.

Core EVSE Rules

Worked Example — Size the Branch Circuit and OCPD for a 40 A EVSE

Given: A hardwired EVSE rated 40 A maximum continuous load, installed in a garage. Copper conductors, 75°C terminations, no more than 3 current-carrying conductors in the raceway.

Step 1 — Continuous-load adjusted current (625.41/625.42):

Formula: Required conductor/OCPD sizing current for this example = EVSE continuous current × 1.25

Substitution: 40 A × 1.25 = 50 A

Step 2 — OCPD selection:

The required OCPD sizing current is 50 A. Per 240.6(A), standard ratings include 50 A. So the OCPD = 50 A.

Step 3 — Conductor selection (Table 310.16, 75°C column, copper):

The conductor ampacity must be ≥ 50 A (the continuous-load value the OCPD protects).

8 AWG copper at 75°C gives exactly 50 A, which meets the requirement. In practice, many installers use 6 AWG (65 A) to provide margin and accommodate voltage drop on longer runs.

Trap: Do not forget that 625.40 requires an individual branch circuit. You cannot share this circuit with a receptacle, lighting, or any other load.

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Load Calculation Cross-References — 120.57 and 240.6(A)

120.57 — EVSE Load Calculation

For 2026 load calculations, use the EVSE nameplate rating under 120.57, including a rating modified in accordance with the permitted 625.42 provisions. If the rating is unknown, use the default load specified by 120.57 before proceeding. The old rule taking the larger of 7200 VA and every known equipment rating should not be carried into the 2026 calculation.

Keep this separate from branch-circuit sizing. A known 40 A, 240 V EVSE contributes 9600 VA to the load calculation. Its ordinary continuous-load branch-circuit example above still needs a 50 A sizing current and suitable conductor/OCPD. These numbers answer different questions.

EVSE does not qualify for the 120.53 fastened-in-place appliance reduction. Under the dwelling optional method, 120.82(D) adds EVSE at 100% of the 120.57 value separately from the general-load demand tiers.

240.6(A) — Standard Ampere Ratings

When selecting an OCPD, use a standard rating from 240.6(A). The full run includes:

15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000

Note: 25 A and 35 A are in the standard list. If your calculation yields 28 A, the next standard rating is 30 A. If it yields 36 A, use 40 A.

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Comparing ESS and EVSE Requirements

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Key Takeaways

• ESS: Remember the 125% multiplier for both OCPD (706.30) and conductors (706.31), and know the disconnect marking text.
• EVSE: Three rules to memorize — individual branch circuit (625.40), continuous-load treatment (625.42), and the separate conductor/OCPD sizing checks.
• 120.57: Determine the equipment rating under the current rule. Keep load calculations separate from conductor/OCPD sizing.
• 240.6(A): Always round up to a standard rating; 25 A and 35 A are standard sizes candidates often forget.

Reference: Mike Holt’s 2026 code-change analysis, including the separate 100% EVSE optional-method load.