EV Charger Circuit Size Calculator
Use this EV charger circuit workflow for early continuous-load screening when EVSE current, voltage, multiplier, and comparison ratings are already known.
- Required circuit ampacity
- A
- EVSE load
- VA
- Adjusted load
- VA
- Entered ampacity margin
- A
- Preferred OCPD margin
- A
Calculation details
- Rating status
- Calculation basis
- Selection boundary
Recent results
Formulas
- Required circuit ampacity = EVSE current x continuous multiplier percent / 100
- EVSE load VA = EVSE current x voltage x phase multiplier
- Adjusted load VA = required circuit ampacity x voltage x phase multiplier
- Entered ampacity margin = entered conductor ampacity - required circuit ampacity
- Preferred OCPD margin = preferred OCPD - required circuit ampacity
Use this calculator
Estimate required circuit ampacity, EVSE load VA, adjusted VA, entered ampacity margin, preferred OCPD margin, and rating status.
Read the result
Review the calculated values with their displayed units and assumptions. The result is a planning aid for the stated inputs, not a final equipment or installation decision.
Check before final work
This EV charger circuit estimate is an arithmetic screen. It does not select conductors, breakers, EVSE settings, load management, dwelling load capacity, permits, utility approval, or code compliance.
FAQs
Does this choose a breaker?
No. It compares the required ampacity against values you enter. Breaker and conductor selection need separate code and equipment review.
Does this check panel capacity?
No. It estimates the EVSE circuit load only. Panel and service load calculations are separate workflows.
Can this approve an EV charger installation?
No. EVSE listing, settings, load management, utility, permit, and local code requirements still need review.