EnoughAmps

What Size EV Charger Do You Actually Need?

Updated · By Dariusz

Most drivers need far less EV charger than the car can accept.1 A charger running at 32 A on 240 V adds roughly 25 miles of range per hour — enough to refill a typical day's driving overnight with hours to spare. Start from the miles you drive, not the biggest charger on the shelf.

Charger size, breaker and range

Charger setting Breaker (125%) Power Range added per hour*
16 A 20 A 3.8 kW ~12 miles
24 A 30 A 5.8 kW ~18 miles
32 A 40 A 7.7 kW ~25 miles
40 A 50 A 9.6 kW ~30 miles
48 A 60 A 11.5 kW ~37 miles

*Assumes about 3.2 miles per kWh; your car may differ.2 The breaker is 125% of the charger current.3

Work out what you need

  1. Take your typical daily miles and add a buffer for the occasional long day.
  2. Divide by the hours the car is usually parked at home overnight.
  3. Pick the smallest setting that covers it.

Example: 50 miles a day, parked 10 hours → 5 miles per hour. Even a 16 A setting covers it twice over.

How chargers count on your panel

Under NEC® 2023 220.57, a charger counts at 7,200 VA or its nameplate rating, whichever is higher.4 So a 48 A charger (11,520 VA) counts noticeably more than a 32 A one (7,680 VA). Many hardwired chargers let the electrician set a lower maximum — often the cheapest fix when the free check comes back yellow or red.

Still short? Compare a load management device and a panel upgrade before you pay for new service.

Technical notes

  1. The DOE Alternative Fuels Data Center notes that some homes have insufficient electrical capacity for Level 2 equipment, that an electrician can confirm it, and that permits may be required. Source: DOE AFDC, charging at home. ↩

  2. The range column assumes 3.2 miles per kWh at the wall (about 31 kWh per 100 miles), a middle value; fueleconomy.gov lists each model's consumption, and DOE notes battery charging efficiency is often 84% to 93%. Source: fueleconomy.gov (DOE/EPA). ↩

  3. EV charging is a continuous load — it can run three hours or more. NEC® 625.41 requires the overcurrent protection for EV supply equipment to be at least 125% of the equipment's maximum load, and the branch circuit conductors are sized the same way (210.19(A)). A DOE site assessment gives the same example: a 32 A unit requires a 40 A breaker. Sources: DOE AFDC EVSE assessment; NFPA 70 (NEC®), free access. ↩

  4. 220.57 was added in the 2023 NEC®. Earlier editions counted chargers at their nameplate with no minimum, which is one reason older load calculations can differ from today's. Berkeley Lab notes most residential Level 2 installations draw 16–48 A on a 20–60 A breaker. Sources: NFPA 70 (NEC®), free access; LBNL technical brief, 2024. ↩

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Panel Capacity Worksheet

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Questions

Can I add an EV charger without upgrading my panel?

Often, yes. The load calculation decides, not the sum of your breakers. If it's tight, a lower charger setting or a load management device can make it fit.

What breaker does a 32 A or 48 A charger need?

EV charging is a continuous load, so the breaker is sized at 125% of the charger current — 40 A for a 32 A charger, 60 A for a 48 A charger.

Does a smaller charger setting lower my load calculation?

Under NEC 2023 an EV charger counts at 7,200 VA or its nameplate, whichever is higher. Settings below 30 A don't lower the calculation further, but setting a 48 A unit to 32 A can.

Sources