Why your car may not use the biggest charger.
Short answer: Every EV has an onboard charger — a piece of hardware inside the car that converts the AC current from your home into DC current the battery can use. The onboard charger has a maximum input rating. Installing a Wall Connector that delivers more current than the onboard charger can accept results in no extra speed. The car simply pulls what it can use. A 48A Wall Connector for a Bolt (which caps at 32A) charges the Bolt at 32A. The extra capacity is wasted.
The chain of math (again, briefly)
Charge rate is determined by the slowest link of three:
- Panel capacity (what your home can deliver)
- Charger rated output (what the wall unit can deliver)
- Car onboard charger cap (what the car can accept)
The slowest link wins. Always.
Onboard-charger cap by car
| Car | Onboard cap | Right install |
|---|---|---|
| Tesla Model 3 / Y / S / X | 48A | 48A Wall Connector |
| Tesla Cybertruck | 48A | 48A Wall Connector |
| Ford F-150 Lightning standard | 48A | 48A |
| Ford F-150 Lightning + Pro | 80A | 80A (only if you have Pro hardware) |
| Ford Mustang Mach-E (2022+) | 48A | 48A |
| Rivian R1T / R1S | 48A real-world | 48A — don't waste on 80A |
| Chevy Blazer / Equinox EV | 48A | 48A |
| Chevy Bolt EV / EUV | 32A | NEMA 14-50 outlet — captures full rate cheaper |
| Hyundai Ioniq 5 / Kia EV6 | 48A | 48A |
| BMW i4 / iX / i5 / i7 | 48A | 48A |
| Mercedes EQE / EQS | 48A | 48A |
| Polestar 2 | 48A | 48A |
The DC fast charging vs home charging confusion
Marketing often quotes a car's "DC fast charging" speed (150 kW, 250 kW, etc.) — that's a different thing. DC fast charging bypasses the onboard charger and feeds the battery directly. Home (AC) charging always goes through the onboard charger and is capped by its rating.
A Tesla Model 3 charges at 250 kW on a Supercharger but only 11.5 kW (48A × 240V) at home. The onboard charger is the limit at home. No amount of wiring effort gets around this.
Why some installers will sell you bigger anyway: commission. The Wall Connector itself costs the homeowner $479 either way; the install labor is similar. The marginal upcharge for "we'll wire you to 100A just to be safe" is small for the installer and adds nothing for the homeowner. Network installers don't do this — the principle is "right-size the install."