Amperage explained
32 A vs 40 A vs 48 A: how many amps do you actually need?
The single most common question in home charging, answered with arithmetic rather than marketing. Bigger is not better if your panel cannot feed it.
By Sawyer V. · Published September 8, 2026
How this page is funded: we earn a commission if you buy through our Amazon links, at no extra cost to you. It does not change what we recommend, and we say plainly when the honest answer is to buy nothing. Full disclosure.
Here is the whole thing in one table, and then the reasoning behind it.
| Charger | Power | Miles per hour | Over 10 hours | Circuit needed |
|---|---|---|---|---|
| 16 A | 3.8 kW | about 13 | about 130 mi | 20 A |
| 24 A | 5.8 kW | about 20 | about 200 mi | 30 A |
| 32 A | 7.7 kW | about 27 | about 270 mi | 40 A |
| 40 A | 9.6 kW | about 34 | about 340 mi | 50 A |
| 48 A | 11.5 kW | about 40 | about 400 mi | 60 A |
The arithmetic, so you can check it
How each row is produced
Power: amps x 240 V / 1000. So 40 x 240 / 1000 = 9.6 kW.
Miles per hour: kW x efficiency. So 9.6 x 3.5 = 33.6, rounded to about 34.
Circuit: amps x 1.25, rounded up to the next standard breaker. So 40 x 1.25 = 50 A.
The 1.25 factor is the continuous-load rule -- an EV charger runs at full current for hours, so the circuit is oversized against it.
Why the fastest option is usually not the right one
Three reasons, in order of how often they apply.
- Your panel may not have 60 amps to spare. Going from a 50 A circuit to a 60 A one can be the difference between a straightforward install and a subpanel or service upgrade -- published figures put a service upgrade at $1,500 to $4,000. That is more than the entire charger.
- Your car may not accept it. The onboard charger in the car sets the ceiling. Plenty of EVs accept 7.7 kW, in which case a 48 A wall unit charges at exactly the same rate as a 32 A one.
- You are asleep. The car is plugged in for ten or twelve hours and you drove 40 miles. Everything on the table above finishes hours before you wake up.
One good charger per tier
Ranked for a first home charger. Every row jumps to the full write-up below.
| # | Product | Best for | Max output | Price |
|---|---|---|---|---|
| 1 | Grizzl-E ClassicHarsh weather and no app. J1772, 24 ft cable. | Harsh weather and no app | 40 A9.6 kW | Check price on Amazon#ad how we are funded |
| 2 | Emporia Level 2 EV Charger (Classic)A first charger, hardwired. J1772, 24 ft cable. | A first charger, hardwired | 48 A11.5 kW | Check price on Amazon#ad how we are funded |
| 3 | ChargePoint Home FlexHomes with an uncertain panel. J1772, 23 ft cable. | Homes with an uncertain panel | 50 A12 kW | Check price on Amazon#ad how we are funded |
When more amps genuinely help
- You regularly drive 150+ miles a day and need a full replacement overnight.
- Two EVs share one charger and both need meaningful charge by morning.
- You tow, which can cut efficiency to well under 2 mi/kWh.
- You are on a narrow off-peak electricity window and want the charging done inside it.
If none of those describe you, buy for your panel and your cable run, and put the savings toward the installation. How many amps do you need walks through checking your panel.
The three units in detail
A solid representative of each amperage tier.
1. Harsh weather and no app
Grizzl-E Classic
United Chargers · J1772 · 40 A / 9.6 kW · 24 ft cable
A cast-aluminum box with no app, no account and no firmware to update. If you want a charger that behaves like an appliance, this is the one.
What is good
- Cast aluminum NEMA 4 / IP67 enclosure, built for outdoor mounting
- No app, no account, no network dependency
- Amperage is set with physical switches, not software
- Protections for over-current, over-voltage, ground fault and over-temperature
What is not
- 40 A ceiling, slower than the 48 A units if your panel can take more
- No scheduling, so off-peak charging has to be set in the car
- The cold-flexible 24 ft cable is only on the Extreme Edition
| Maximum output | 40 A / 9.6 kW at 240 V |
|---|---|
| Adjustable | 16, 24, 32 or 40 A |
| Connector | SAE J1772 |
| Cable | 24 ft on the Extreme Edition |
| Enclosure | Cast aluminum, NEMA 4 / IP67 |
| Certification | UL certified |
| Warranty | 3 years |
Skip this if: Skip it if you want scheduled charging or energy tracking in an app. The Classic deliberately has neither.
Specifications above are the manufacturer’s published figures. Source: United Chargers, InsideEVs. We have not tested this unit — see how we pick.
2. A first charger, hardwired
Emporia Level 2 EV Charger (Classic)
Emporia · J1772 · 48 A / 11.5 kW · 24 ft cable
The safe default for a first home charger: 48 amps hardwired, a genuinely long cable, a NEMA 4 outdoor-rated case, and no subscription attached to the app.
What is good
- 48 A hardwired is the fastest tier most homes can realistically support
- 24 ft of cable reaches across a two-car garage without a fight
- NEMA Type 4 enclosure is rated for outdoor mounting
- Energy monitoring in the app with no subscription
What is not
- Drops to 40 A if you use the NEMA 14-50 plug rather than hardwiring
- The app is the only way to change the amperage setting
| Maximum output | 48 A / 11.5 kW at 240 V (hardwired) |
|---|---|
| Plug-in output | 40 A with the NEMA 14-50 plug |
| Connector | SAE J1772 |
| Cable | 24 ft |
| Enclosure | NEMA Type 4, indoor or outdoor |
| Certification | UL listed, Energy Star |
| Warranty | 3 years |
Skip this if: Skip it if you want a unit with no app or network connection at all. The Grizzl-E Classic is the simpler machine.
Specifications above are the manufacturer’s published figures. Source: Emporia Energy. We have not tested this unit — see how we pick.
3. Homes with an uncertain panel
ChargePoint Home Flex
ChargePoint · J1772 · 50 A / 12 kW · 23 ft cable
The most adjustable unit here. It can be set anywhere from 16 A to 50 A, which makes it the one to buy when you do not yet know what your panel will allow.
What is good
- Six selectable amperage settings from 16 A to 50 A
- Sold in both hardwired and NEMA 14-50 versions
- Rated for indoor or outdoor installation
- The app is mature and does not require a subscription
What is not
- 23 ft is a foot shorter than the longest cables in this group
- The 50 A setting needs a bigger circuit than most panels have spare
| Maximum output | 50 A / 12 kW at 240 V |
|---|---|
| Amperage settings | 16, 24, 32, 40, 48 or 50 A |
| Connector | SAE J1772 |
| Cable | 23 ft |
| Installation | Hardwired or NEMA 14-50 |
| Certification | UL listed, Energy Star |
| Warranty | 3 years |
Skip this if: Skip it if your circuit is already fixed and you just want the cheapest safe 40 A unit. You are paying for flexibility you will not use.
Specifications above are the manufacturer’s published figures. Source: ChargePoint, ChargePoint. We have not tested this unit — see how we pick.
FAQ
Questions people actually ask
Is a 48-amp charger worth it over 40 amps?
What circuit does a 32-amp EV charger need?
How many miles per hour does a 40-amp charger add?
Can my car use a 48-amp charger?
Sources
Where these numbers come from
- NEC Article 625: EV charging equipment — WireRefThe continuous-load rule behind every circuit figure in the table.
- NEC 125% rule for EV charger breaker and wire sizing — Electric Vehicle GeekPublished sizing ladder corroborating the circuit column. Fetched 2026-09-08.
- Level 2 EV charger installation cost, 2026 — SimpleSwitchPublished service-upgrade cost range cited above.
Read next
Related reading
- How many amps do you actually need?Three checks that determine your charger amperage, and why the smallest one wins.
- What size breaker and wire does an EV charger need?Breaker and wire size for every charger amperage, with the 125% rule worked through.
- EV charging speed calculatorCalculate charging speed and time from your own numbers, with the working shown.
- The best home EV chargers, for people buying their first oneSix Level 2 chargers ranked for a first-time buyer, with an honest reason to skip each one.