EV Charging Panel Load Calculator
Check whether your electrical panel can handle an EV charger: continuous circuit load, the 80% code limit, and remaining spare capacity.
How it works
Continuous ceiling = panel × 80% · Load with EV = existing + charger amps · Breaker = charger amps × 125%
An EV charger is a continuous load, so code sizes its breaker at 125% of the charger current and limits sustained draw on the service to 80% of its rating. The practical test is whether your existing peak demand plus the charger’s draw stays under that 80% ceiling. If it does not, you can drop to a lower charger amperage, add a load-management device that pauses charging under peak, or upgrade the service.
Worked example
On a 200 A panel the continuous ceiling is 200 × 0.8 = 160 A. With a 90 A existing peak, a 48 A charger brings you to 138 A — under 160 A, so it fits with 22 A to spare. The charger itself needs a 48 × 1.25 = 60 A breaker, and at 240 V delivers 11.5 kW.
Frequently asked questions
Why size the breaker at 125% of the charger current?
The US electrical code treats a load running three hours or more as continuous and requires the circuit to be rated at 125% of that load. A 48 A charger therefore needs a 60 A breaker and wiring, even though it only draws 48 A.
What if my panel can’t take the extra load?
You have three common options: set the charger to a lower amperage (many are adjustable), install a load-management system that pauses EV charging when the house nears its limit, or upgrade the electrical service. A licensed electrician should run a full load calculation first.
How do I find my existing peak load?
The most accurate way is a NEC load calculation or a review of interval data from your utility, which shows your real demand peaks. Nameplate ratings of every appliance overstate it, since they rarely all run at once.
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This calculator is for educational purposes. Double-check important results before acting on them.