Can a 100-amp panel handle a Level 2 EV charger?
Often yes, but rarely at the full 48 A. Under NEC 220.87 a charger adds its amps × 1.25 on top of 125% of your existing metered demand. On a 100 A service with a 60 A peak demand, that is 75 A already used, leaving 25 A — enough for a ~16 A charger at full output, or the full charger with a load-management (EMS) device that throttles it when the house is busy.
What is NEC 220.87 and when can I use it?
220.87 sizes new load from your building's actual maximum demand instead of a paper calculation. You need at least a full year of the utility's recorded demand (or, where that isn't available, a minimum 30-day recording at 15-minute intervals during the peak season). The calculated load is 125% of that peak demand plus the new charger. It usually gives the most headroom because it reflects how the home really runs.
Do I need a service upgrade to install an EV charger?
Not necessarily. NEC 625.42 allows an energy-management system (EMS) or load-sharing device that limits the charger when the rest of the panel is loaded, so you can add a charger without upsizing the service. Lowering the charge rate (most 48 A units field-set to 40, 32, or fewer amps) is the other no-upgrade path. A service upgrade is the last resort — and the only option once your existing demand alone reaches the service rating.
What breaker does a 48-amp EV charger need?
A 60 A breaker. An EVSE is a continuous load, so the branch circuit and its overcurrent device are sized at 125% of the charger's continuous output: 48 × 1.25 = 60 A, which is a standard size. A 40 A charger needs 50 A, a 32 A charger needs 40 A. Size the conductors for the same 125% with the wire-size calculator.
Which method should I use — 220.87 or 220.83?
Use 220.87 if you can get a year of demand data from your utility; it is the most accurate. Use 220.83 (the optional dwelling calculation) when you can't — it estimates existing load from floor area plus appliance nameplates, taking 100% of the first 8 kVA and 40% of the rest, with the larger of A/C or electric heat at 100%. This tool runs whichever one you have the inputs for.
Why is the charger load multiplied by 1.25?
Because an EV charger runs at its maximum current for three hours or more, the NEC classifies it as a continuous load (625.42). Continuous loads are added to a service or feeder calculation at 125% of their rated current, which is why a 48 A charger counts as 60 A of demand, not 48 A.