A quick, rough check using a simplified version of the optional dwelling load calculation (NEC 220.82). It is not a real load calculation, but it shows whether you are probably fine, tight, or likely over.
Rough, not a load calculation. Simplified NEC 220.82: 3 VA per sq ft, 2 small-appliance circuits and 1 laundry circuit at 1,500 VA each, plus the appliance nameplates you enter; the first 10 kVA at 100% and the rest at 40%; plus the largest heating or cooling choice from NEC 220.82(C): AC at 100%, a heat pump at 100% plus 65% of backup strips that can run with it, electric heat at 65% (40% with four or more separately controlled units). Divided by 240 V. Your real answer depends on nameplates, the panel's busbar and spaces, and the electrician's calculation, or a year of utility demand data (NEC 220.87). Load management (EVEMS, NEC 625.42 / 220.70) can often avoid a service upgrade.
What if my panel is too small?
Options include a smaller charger setting, a load-management device, a subpanel if capacity allows, or a panel or service upgrade. IES can do an EV panel capacity evaluation, and a 200-amp service upgrade starts at $6,500.
About these prices: rough starting-at prices from the IES price book. The final price depends on what we find on site, your utility and your city or county. Estimates are free.
Common questions
Can a 100 amp panel handle an EV charger?
Sometimes. Many 100-amp homes with gas appliances can add a modest charger, often with load management. Homes with electric range, dryer, water heater and AC usually need a load calculation and may need an upgrade.
General information for California homes under the California Electrical Code (based on the NEC). Local rules and inspectors can vary. Not a substitute for an on-site inspection. Never work inside a panel, at the meter or on live circuits.