Once you’ve decided to install a Level 2 charger, the next big question is amperage. It’s the single spec that determines your charging speed, your equipment cost, and how much work your electrician needs to do on your electrical panel. Here’s how to figure out the right number for your situation — without guesswork.
Why Amperage Matters So Much
Amperage determines how much current flows to your car at any given moment. Higher amperage means faster charging, but it also means:
- A more expensive charger unit
- A heavier-gauge, more expensive circuit and wiring
- A higher chance you’ll need an electrical panel upgrade
- A higher installation cost overall
In other words, more amps isn’t automatically “better” — it’s a trade-off between charging speed and cost that should match your actual driving needs, not the highest number available.
Common Amperage Options for Home Chargers
| Amperage | Approx. range added per hour | Typical use case |
|---|---|---|
| 16 amps | 10 – 15 miles | Light daily driving, plug-in hybrids |
| 24 amps | 15 – 20 miles | Moderate daily driving |
| 32 amps | 20 – 30 miles | Most common choice for single-EV households |
| 40 amps | 25 – 35 miles | Larger batteries, longer commutes |
| 48 amps | 30 – 40 miles | High-usage households, larger EVs |
| 60 amps | 35 – 45+ miles | Multiple EVs, very high daily mileage |
Keep in mind that your actual charging speed is capped by whichever is lower: the charger’s amperage output or your vehicle’s onboard charger capacity. A 48-amp charger connected to a car that can only accept 32 amps will charge at 32 amps — the extra capacity simply goes unused (though it does leave room if you upgrade vehicles later).
The 80% Rule: Why Circuits Are Rated Higher Than the Charger
You’ll often see a charger’s amp rating and its required circuit breaker size listed as different numbers — for example, a “40-amp charger” that requires a 50-amp breaker. This isn’t a mistake. U.S. electrical code (NEC 625) requires continuous loads like EV charging to run at no more than 80% of the circuit’s rated capacity. So:
- A 40-amp charger needs a 50-amp breaker (40 ÷ 0.8 = 50)
- A 48-amp charger needs a 60-amp breaker (48 ÷ 0.8 = 60)
This safety margin prevents circuits from overheating during the long, continuous draw that EV charging requires — very different from a typical household appliance that cycles on and off.
How to Figure Out What You Actually Need
Rather than defaulting to the highest amperage available, work through these three questions:
1. What’s your daily driving distance?
Add up a typical day’s driving, then check it against the “range per hour” column above, multiplied by your expected charging window (usually 6-10 hours overnight). If you drive 40 miles a day and charge for 8 hours, even a 24-amp charger (roughly 160 miles of overnight capacity) comfortably covers your needs with room to spare.
2. What can your vehicle’s onboard charger actually accept?
Check your EV’s specifications — most manufacturers list a maximum AC charging rate (commonly 32, 48, or 80 amps depending on the model). There’s no benefit to buying a charger that exceeds what your car can use, unless you’re planning ahead for a future vehicle.
3. What can your electrical panel support?
This is the practical constraint that often matters most. Panels have a limited total capacity, and adding a large new circuit for EV charging may require a panel upgrade if you’re already close to your home’s electrical limit. A licensed electrician can perform a load calculation to confirm exactly what your panel can handle — we walk through this process in our guide on whether you need a new electrical panel for an EV charger.
A Practical Recommendation
For most single-EV households with an average U.S. commute (around 30-40 miles round trip), a 32-amp charger on a 40-amp circuit hits the sweet spot: fast enough to fully recharge overnight, without paying for capacity you’ll rarely use or triggering a costly panel upgrade.
Consider sizing up to 40-48 amps if:
- You drive significantly more than average
- You own or plan to own a larger-battery EV or truck
- You have, or plan to add, a second EV in the household
- You occasionally need a fast partial charge before a same-day trip
Key Takeaways
- Amperage controls charging speed, but your car’s onboard charger and your panel’s capacity both cap what you can actually use.
- U.S. code requires circuits to be sized at 125% of the charger’s rated amperage (the “80% rule”).
- Most single-EV households are well served by a 32-40 amp setup — going higher only pays off with above-average driving needs or multiple EVs.
- A licensed electrician’s load calculation is the definitive way to know what your home can support before you buy.
