EV charger size by breaker and panel capacity
Short answer: Set the charger to no more than 80% of the breaker rating: 24 A on 30 A, 32 A on 40 A, 40 A on 50 A, 48 A on 60 A. NEC 625.41 requires overcurrent protection of at least 125% of the charger's load, and 625.42 treats EV charging as continuous.
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| Breaker (240 V) | Max charger setting | Power | Math | Shop |
|---|---|---|---|---|
| 30 A | 24 A | 5.8 kW | 30 A ÷ 1.25 = 24 A; 24 A × 240 V = 5.8 kW | — |
| 40 A | 32 A | 7.7 kW | 40 A ÷ 1.25 = 32 A; 32 A × 240 V = 7.7 kW | — |
| 50 A | 40 A | 9.6 kW | 50 A ÷ 1.25 = 40 A; 40 A × 240 V = 9.6 kW | — |
| 60 A | 48 A | 11.5 kW | 60 A ÷ 1.25 = 48 A; 48 A × 240 V = 11.5 kW | — |
Level 1 on a 120 V receptacle: max 12 A / 1.4 kVA on a 15 A receptacle, 16 A / 1.9 kVA on a 20 A receptacle (Brookline code excerpt). Source: Town of Brookline, MA – Electrical Code excerpt (NEC 625.41/625.42, official PDF) (accessed 2026-10-25).
Panel capacity
Whether a 100 A or 200 A panel can take a new 40–60 A circuit depends on a load calculation by a licensed electrician. We have no official threshold, so that part is data pending. If you do need an upgrade, national cost data:
| Source | Figure |
|---|---|
| Qmerit (national) | A panel upgrade adds $1,500–$3,000 to a Level 2 charger install. |
| HomeAdvisor (an Angi brand, national) | Panel replacement $518–$2,194 (average $1,347); 200A upgrade $1,300–$2,000; 100A→200A $750–$2,000 excluding new circuits; permits and drywall add $150–$300. Page dated “Updated Jun 17, 2026”. |
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Last checked: 2026-10-25. Always follow the charger's install manual and local code. Product links appear only once a partner is set (disclosure).
What size breaker do I need for a 40 amp EV charger?
A 50 A breaker. NEC 625.41 requires overcurrent protection of at least 125% of the charger's maximum load (40 A × 1.25 = 50 A).
Can I put a 48 amp charger on a 50 A breaker?
No. 48 A × 1.25 = 60 A, so a 48 A charger needs a 60 A circuit.
Is my 100 A panel big enough?
No fixed rule: an electrician must do an NEC load calculation. We have no sourced threshold, so that is data pending.