What Amperage EV Charger Do I Need?

What amperage EV charger do I need?

Charge speed is amperage, but more isn't automatically better. Here's how the car, your Bend panel's available capacity, and the 125 percent continuous-load rule set the right circuit — and why 48 amps isn't always the answer.

Bend EV Charger Crew

Local licensed electricians serving Deschutes County · Bend, OR

(541) 555-8877

The right EV charger amperage is set by three things: what your car can accept on AC charging, how much capacity your panel can spare, and the 125 percent continuous-load rule that sizes the circuit. Common residential circuits are 20, 30, 40, or 48 amps. Bigger isn't automatically better — a 48-amp charger only charges faster if both the panel and the car support it. The honest number comes from a load calc, not the box on the shelf.

Charge speed is amperage, not the brand

On Level 2, charging speed scales with the circuit amperage. A 40-amp circuit delivers more power than a 20-amp one, and the EVSE on the wall can only pull what the circuit and the panel allow. The charger brand barely matters to speed; the amperage of the circuit feeding it does. That's why "what amperage do I need" is the real question, and why buying the biggest charger on the shelf before sizing the circuit puts the cart before the horse.

An EV charger amperage setting and a circuit breaker — Charge speed is amperage. A 40-amp circuit charges faster than a 20-amp one, but the EVSE can only pull what the circuit and the panel allow — the dial is set by the wiring, not the box.

What the car can accept

Your EV's onboard charger caps how many amps it can pull on AC charging, and that ceiling varies by model and trim. Running a circuit above what the car accepts charges no faster — it just costs more in wire. So the first input to the right amperage is the vehicle: a car that tops out around 32 or 40 amps gains nothing from a 48-amp circuit. We ask which EV you're charging precisely so we don't oversize the circuit past what the car can use.

A double-pole breaker sized for an EV charger circuit — A Level 2 charger is a continuous load, so the circuit is sized to 125 percent of the draw: a 48-amp charger needs a 60-amp breaker and the wire to match. The 125 percent rule is why amperage drives wire cost.

What the panel can spare

The second input is your panel's available capacity. A load calculation shows how much the service can spare for an EV circuit after the existing loads. A modern 200-amp panel with headroom may carry a 48-amp circuit; a fuller or older panel may only support 30 or 40 amps, or need an upgrade first. The amperage you can run is the smaller of what the car accepts and what the panel can spare — never more than the weaker of the two. We cover the panel side in do I need a panel upgrade.

An EV charging port on a vehicle in a garage — The car matters too: most EVs accept a ceiling on AC charging, so running more amps than the vehicle can take just pays for copper you can't use in a Bend install.

The 125 percent continuous-load rule

An EV charger is a continuous load — it draws steadily for three or more hours — so the National Electrical Code sizes the circuit to 125 percent of the charger's rated draw. That's why a 48-amp charger needs a 60-amp breaker and matching wire, a 40-amp charger needs a 50-amp circuit, and a 32-amp charger needs a 40-amp circuit. The rule isn't padding; it keeps the wire from running hot under a long continuous draw, and it's why higher amperage means heavier, costlier copper.

Landing on the right number

Put the three inputs together: take the lower of what your car accepts and what your panel can spare, then size the circuit to 125 percent of that. For many Bend drivers a 40-amp circuit is the sweet spot — real overnight charging without overbuilding. The biggest number is only the right number when the car and the panel both support it. Tell us the car and the panel and we'll size it honestly on the phone, then handle the Level 2 install permitted and inspected. If you're still deciding outlet versus hardwire, see hardwired vs NEMA 14-50.

Frequently Asked Questions

What amperage EV charger do I need?

The right amperage is set by three things: what your car can accept on AC charging, how much capacity your panel can spare, and the 125 percent continuous-load rule that sizes the circuit. Common residential EV circuits are 20, 30, 40, or 48 amps. The honest answer comes after a load calc — buying a 48-amp charger for a panel that can spare 24 amps, or a car that caps lower, just leaves capacity unused.

Is a 48-amp charger always better than a 40-amp one?

No. A 48-amp charger only charges faster if your panel can carry a 60-amp circuit and your car can accept 48 amps on AC. If either falls short, the extra amperage does nothing but cost more in wire. For many Bend drivers a 40-amp circuit fully recovers a day's driving overnight, so the "biggest number" isn't automatically the right one — the right one is what the car and panel justify.

What is the 125 percent rule?

An EV charger is a continuous load — it draws for three or more hours — so the National Electrical Code requires the circuit to be sized to 125 percent of the charger's rated draw. That's why a 48-amp charger needs a 60-amp breaker and wire, a 40-amp charger needs a 50-amp circuit, and so on. It's not optional padding; it's how the wire stays cool under a long continuous draw.

How do I find out what my car can accept?

Your EV's onboard charger sets a ceiling on how many amps it can pull on AC (Level 2), and it varies by model and trim. Running a circuit above that ceiling won't charge any faster. We ask which vehicle you're charging so we size the circuit to what the car can actually use, not just what the panel could theoretically deliver — that's part of getting the amperage right rather than oversized.