32-Amp vs 40-Amp EV Charger

Most amperage comparisons are about speed. This one is not, really — seven miles of range per hour is not the sort of difference anyone notices across a night. This one is about which circuit you need, and that is a question with a price attached.

The 80% rule is the whole story

Under the NEC, EV charging is a continuous load, so the circuit is sized at 125% of the charger’s current. Thirty-two amps needs a 40-amp breaker; forty amps needs a 50.

Read backwards, that is the most useful shopping rule on this site: breaker rating × 0.8 = charging amps. If your panel can spare a 40-amp double-pole breaker, you can have 32 amps of charging. If it can spare 50, you can have 40.

Which is why this comparison matters more than the speed gap suggests. Going from 32 to 40 amps means a bigger breaker, usually a heavier conductor — 6 AWG rather than 8 for a typical copper run — and one more slice of your panel’s capacity committed permanently. Our panel capacity guide covers whether that slice is available.

What the speed difference actually looks like

Thirty-two amps is 7.7 kW, about 27 miles of range per hour at our reference efficiency. Forty amps is 9.6 kW, about 34.

Across a ten-hour overnight window that is roughly 270 miles against 340. Both numbers are far beyond what an average day consumes, which is the honest framing: for the great majority of households, both chargers finish the job while you are asleep and the difference is invisible.

It becomes visible in four situations, and only four:

• Very high daily mileage— over roughly 250 miles a day, where you start to consume the whole window.
• Two cars sharing one charger, where the window is split. See our two-car roundup.
• A short window at home— shift work, or a car that leaves early.
• A narrow off-peak rate window, where fitting the entire session inside the cheap hours is worth money. That case is in time-of-use charging.

Check the car before you decide anything

The comparison is moot if the vehicle cannot use the difference. Your car’s onboard chargersets an absolute ceiling on AC charging, and a great many EVs and nearly all plug-in hybrids are rated at or below 7.7 kW — which is exactly 32 amps.

If that is your car, a 40-amp charger delivers identical sessions to a 32-amp one and the extra circuit capacity buys nothing at all. Look the rating up in the owner’s manual first; the reasoning is in the charger is inside your car.

The answer most people should take

Buy an adjustable charger and let the circuit decide.

Almost every good charger now sets its output over a wide range — EVIQO’s plug-in 40A adjusts from 6 to 40 amps in the app, Grizzl-E’s Smart offers 16, 24, 32 and 40 on a DIP switch, and ChargePoint’s Home Flex spans 16 to 50. Any of them runs at 32 amps on a 40-amp circuit today and moves to 40 later with a setting change and, if the circuit is upgraded, an electrician’s visit.

That is the correct way to buy headroom. What is not correct is installing a larger circuit than you need on the strength of a hypothetical future car. Conductors and breakers are where the money is; the setting is free. Install what you can justify, buy a charger that can be raised, and revisit it if the second EV actually arrives.

Quick picks

Ranked on published specs, charging speed, electrical fit and value. Select a row to jump to the full write-up. We have not bench-tested these chargers — here is exactly what we do instead.

#	Product	Best for	Price
1	EVIQO 40A NEMA 14-50 Charger The most charger you can get without an electrician's invoice. It plugs into a NEMA 14-50 outlet for a full 40 amps, keeps the WiFi app, the ENERGY STAR listing and the 25 ft cable from EVIQO's hardwired unit, and can be unplugged and taken with you when you move.	Adjustable 6-40A, plug-in, best all-rounder here	$449.99 · View on Amazon $510.9912% off Price as of October 18, 2026. #ad How we’re funded
2	Grizzl-E Classic Connect 40A Grizzl-E's cast-aluminum build with a WiFi radio in it. You get the IP67 body and the cold-flexible 25 ft cable that made the brand's name, plus scheduling, usage history and utility demand-response programs in the Grizzl-E Connect app — in a plug-in unit that comes off the wall when you move. The amperage is still set with a DIP switch, which is either charmingly honest or annoyingly analog depending on your taste.	16/24/32/40A on a DIP switch, cast-aluminum body	$349.99 · View on Amazon Price as of October 18, 2026. #ad How we’re funded
3	ChargePoint Home Flex The safest default for most homes: you set the amperage in the app to 16, 24, 32, 40, 48 or 50A, so one charger fits whatever circuit your panel can spare today and scales up if you upgrade later. The app is the most mature here, firmware arrives over the air, and the warranty is long.	Widest range of all — 16A to 50A	$516.71 · View on Amazon Price as of October 18, 2026. #ad How we’re funded

The verdict, by situation

• Your panel can spare 50 amps and the car accepts it: take the 40. The extra costs little at install time and the headroom is genuinely there.
• Your panel can spare 40 amps: 32 amps, without regret. It is real Level 2 charging and it will not slow your life down.
• Your car caps at 7.7 kW: 32 amps. Anything more is capacity you install and never use.
• You are not sure yet: buy adjustable, install the circuit you can justify today. This is the answer for most people.
• Two EVs, or very high mileage: neither — look at 48 amps and read 40 vs 48, remembering that 48 amps must be hardwired.

And if the panel answer came back discouraging, do not assume Level 2 is off the table. A 24-amp charger on a 30-amp circuit still adds around 20 miles of range an hour, several times what Level 1 manages — our small-panel roundup covers that ground.