J1772 vs NACS: EV Connector Standards Deep Dive
The Short Answer
SAE J1772 has been the North American AC charging standard since 2009. NACS (now SAE J3400), originally developed by Tesla, is rapidly becoming the new industry standard after mass OEM adoption. Both use the Control Pilot protocol for AC charging, but NACS integrates AC and DC into a single compact connector where J1772 requires a separate CCS Combo 1 inlet for DC.
The connector standard your customer's vehicle uses determines what EVSE hardware you install and how the circuit communicates with the car. In 2026, both J1772 and NACS are active in the field — and understanding both is essential for any working EVSE installer.
J1772 (SAE J1772) is a 5-pin AC connector handling Level 1 and Level 2 charging via a Control Pilot signal. NACS (SAE J3400) is a smaller 3-pin connector that handles both AC Level 2 charging and DC fast charging through the same port using a different pin arrangement. NACS is now the factory standard on most new US-market EVs from Ford, GM, Honda, Nissan, and others.
J1772 Pin Assignments and Control Pilot Protocol
| Pin | Function | Voltage / Signal |
|---|---|---|
| L1 (Line) | AC hot conductor | 120/240 V AC |
| Neutral (N) | AC return (L1 single-phase) | 0 V reference |
| L2 (Line) | Second AC hot (240 V) | 240 V AC |
| Ground (PE) | Protective earth (first to connect) | 0 V / safety |
| CP (Control Pilot) | PWM signal; communicates EVSE capacity and vehicle state | ±12 V, 1 kHz PWM |
| PP (Proximity Pilot) | Detects cable connection; cable current rating | Resistor-encoded |
Control Pilot States
The CP signal encodes the charging state in both its voltage level and duty cycle. State A (+12 V DC, no vehicle) → State B (+9 V, vehicle connected, not ready) → State C (+6 V, vehicle ready, EVSE energizes) → State D (+3 V, ventilation required — rare) → State E/F (error/EVSE not ready). The PWM duty cycle encodes available current: 10–85% duty = 6–51 A capacity.
NACS / SAE J3400 Architecture
NACS uses three primary conductors in a compact housing: two power conductors (which carry AC or DC depending on mode) and a ground. The signaling protocol for AC charging mirrors J1772 CP/PP logic so EVSE firmware can support both standards. For DC fast charging, NACS uses the same power pins with a different signaling handshake — eliminating the need for the separate large CCS Combo 1 DC pins.
CCS Combo 1 (DC) vs NACS DC
| Attribute | CCS Combo 1 | NACS DC |
|---|---|---|
| DC Pins | 2 large additional pins below J1772 | Same 2 pins as AC (shared) |
| Connector Size | Large / bulky | Compact |
| Max Power (2026) | 350 kW | 250 kW (expanding) |
| Protocol | DIN 70121 / ISO 15118 | Proprietary → ISO 15118-20 |
| Vehicle Adoption (US) | Declining for new models | Dominant for 2025+ models |
What This Means for EVSE Installers
- Level 2 EVSE with J1772 outlets: still fully functional via NACS-to-J1772 adapters (SAE J3400 mandates adapter compatibility)
- New commercial projects: specify dual-port EVSE (one J1772, one NACS) or NACS-only for future compatibility
- DC fast chargers: verify connector options — most new DCFC units offer both CCS and NACS ports
- Existing J1772-only commercial sites: may need hardware upgrades as fleet NACS-native vehicles grow
- Circuit design does not change — the NEC 625 / 220 calculations are connector-agnostic
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Frequently Asked Questions
Can a NACS vehicle charge on a J1772 EVSE?
Yes, with an adapter. SAE J3400 (NACS) requires that vehicles and chargers support adapter interoperability. Most NACS-native vehicles ship with or can purchase a NACS-to-J1772 adapter for use on existing Level 2 equipment.
Will J1772 EVSE become obsolete?
Not immediately. J1772 Level 2 equipment remains fully functional via adapters and will be in service for many years. However, new commercial installations should plan for NACS compatibility given the pace of OEM adoption.
Does the NACS transition affect how I size circuits?
No. The NEC 625 continuous-load calculations, conductor sizing, and breaker sizing are based on the EVSE's power output rating — not the connector type. A 48 A NACS charger uses the same 60 A circuit as a 48 A J1772 charger.
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Michael Rivera
Texas Master Electrician with 12+ years in the trade and 500+ EV charger installations. Lead instructor at EVCharger Academy.
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