Free tool

Will my service carry an EV charger?

The question an inspector asks before the permit is issued. Enter your service, what the house already pulls, and the charger you want. You get the total load, whether it fits, and the largest charger that does.






Your utility account lists this as peak demand or maximum demand, measured over fifteen minutes. No idea? A house without electric heat usually sits between 8 and 12 kW.

0 A
Enter your existing demand
Enter a service

Existing load0 A
At 125 percent0 A
Charger at 125 percent0 A
Headroom left0 A
Breaker needed0 A

Where to find your peak demand. Log in to your utility account and look for peak demand, maximum demand, or demand history. It is the highest fifteen minute average of the past twelve months, and NEC 220.87 lets that figure stand in for a full load calculation on an existing home. If your utility does not publish it, an electrician can meter the service for thirty days instead.

Why 125 percent. An EV charger runs for hours at a time, which makes it a continuous load, so the circuit and the breaker are sized at 125 percent of its output under NEC 625.42. A 40 amp charger needs a 50 amp breaker and conductors to match. The existing house load is taken at 125 percent for the same reason under 220.87.

If it does not fit. Load management is usually the cheapest answer. The charger throttles or pauses while the rest of the house is drawing current, and the reduced figure is what counts as the load. A smaller charger is the next option, and a service upgrade is the last one.

What this does not do. It does not size your conductors, check whether your panel has a spare slot or enough busbar rating, or account for a subpanel between the service and the charger. It answers one question: does the service carry it.