The short answer
A 40 A charger's output cord is typically 8 AWG, which matches NEC Table 310.16's 50 A ampacity for 8 AWG copper at 75 degC. The relationship is simple: thicker conductor, lower resistance, less heat, higher safe current. On a cable you are buying, the gauge is a useful sanity check on the amp rating — a cable claiming 50 A with thin conductors is claiming something the physics does not support.
Gauge, in one table
| Gauge | 60 degC | 75 degC | 90 degC | Typical EV use |
|---|---|---|---|---|
| 12 AWG | 20 A | 25 A | 25 A | A 16 A portable charger |
| 10 AWG | 30 A | 35 A | 40 A | A 24 A circuit |
| 8 AWG | 40 A | 50 A | 55 A | A 40 A charger's output cord; a 40-50 A circuit |
| 6 AWG | 55 A | 65 A | 75 A | A 48 A charger's branch circuit |
| 4 AWG | 70 A | 85 A | 95 A | A 64 A circuit |
| 3 AWG | 85 A | 100 A | 110 A | An 80 A circuit |
Why the Grizzl-E publishes “8 AWG output cord”
It is one of the few manufacturers that does, and it is a meaningful disclosure. The Grizzl-E Classic is a 40 A charger with a 24 ft, 8 AWG output cord — 8 AWG carries 50 A at 75 degC, so there is headroom over the 40 A the charger delivers.
Most manufacturers publish the cable's length and not its gauge, which is why the gauge is worth asking about on a cable you are buying separately.
The difference between a charger cord and building wire
Worth being clear about, because the same gauge numbers appear in both contexts and the products are not comparable.
| Charger output cord | Branch-circuit conductor | |
|---|---|---|
| Where | From the charger to the car | From the panel to the charger |
| Construction | Highly flexible, fine stranding, flexible jacket | Stranded or solid, fixed in place |
| Governed by | The charger's listing (UL 2594) | NEC Table 310.16 and Article 625 |
| Who chooses it | The manufacturer | Your electrician |
| Typical gauge at 40 A | 8 AWG | 8 AWG in conduit; 6/2 NM-B |
| Replaceable | Rarely | n/a |
Why gauge matters more on a long cable
Two separate effects, and both get worse with length:
- Heat. Resistance generates heat proportional to the square of the current. At 40 A continuous for eight hours, a thin conductor gets meaningfully warmer than a thick one.
- Voltage drop. A longer conductor drops more voltage, which means the car sees slightly less than 240 V and charges slightly slower. On a 25 ft charger cord it is negligible; on 25 ft of cord plus 30 ft of extension it is not.
That compounding is the real argument against long extension chains — see are EV charger extension cords safe.
What to look for when buying a cable
- A published amp rating with headroom over your charger's output. 50 A rated on a 48 A charger.
- A UL listing on an extension cable, or UL 2594 / ETL on a portable cordset. The US DOE's guidance recommends safety-certified equipment tested by a nationally recognized laboratory.
- A published gauge, if available. It is a sanity check: a cable claiming 50 A should have conductors capable of it.
- Weight. A heavier cable at a given length usually means thicker conductors, and in this category that is the right direction.
- A sensible jacket. It has to flex at 10 degF and resist being driven over.
What we would buy
Cables where the rating is backed by a listing
The SEGUMA extension is 50 A rated and UL listed, which is the combination that matters. The supply-side NEMA 14-50 extension is the lower-risk way to add length to a plug-in charger.
The extension to pick if you must use one
SEGUMA J1772 Extension Cable (21 ft, 50 A, UL listed)
50 A rated and UL listed, which is the combination to insist on: the rating has headroom over a 48 A charger and the listing means something tested it.
#ad Price as of October 5, 2026. How we make money
Extending the supply side, not the vehicle side
CircleCord 50 A NEMA 14-50 Extension Cord (25 ft)
A 50 A NEMA 14-50 extension — the better place to add length than the J1772 side, because it sits before the charger's own protection rather than after it.
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