How do I size a Level 2 EV charger circuit at my ADU?

Start with the charger's rated current: the 2023 NEC requires an individual branch circuit for Level 2 chargers, protected by a breaker rated at least 125 percent of the charger's maximum load because charging is a continuous load. In the load calculation, the charger counts at 7,200 watts or its nameplate rating, whichever is larger, unless an energy management system limits it.

First: is EV charging required for your ADU?

Usually not. The 2025 California Electrical Code sends new-construction EV rules to CALGreen, and CALGreen Section 4.106.4 Exception 2 exempts ADUs and JADUs built without additional parking facilities. Some cities amend that exemption, for example by applying electrical capacity requirements when a panel is upgraded or a new panel is installed, so check your local rules. If you are adding a charger by choice, the sizing rules below still apply.

Circuit sizing basics

• Individual circuit. Section 625.40 requires an individual branch circuit for each outlet supplying charging equipment rated over 16 amps or over 120 volts, unless an energy management arrangement permitted by Section 625.42 lets chargers share.
• The 125 percent rule. Section 625.41 sizes overcurrent protection for continuous duty at no less than 125 percent of the equipment's maximum load. A charger that draws 32 amps continuously needs at least a 40-amp breaker (32 × 1.25 = 40), and the conductors are sized for that breaker.
• Adjustable chargers. Some Level 2 chargers can be set by the installer to a lower maximum current. A lower setting means a smaller breaker and less load, which can decide whether the charger fits on your existing panel.
• Hardwired or plug-in. Either can work. Follow the charger's listing and installation instructions and the code's protection rules for the type you choose.

Load calculation and energy management

Section 220.57 counts charging equipment at 7,200 watts or nameplate, whichever is larger. If that pushes the total past your service rating, Section 625.42 and Article 750 allow an energy management system to limit the charger's draw, and Section 220.70 lets the load calculation use the system's setpoint. PG&E also describes meter socket adapters as a possible alternative to a panel upgrade when connecting EV chargers, so ask your utility whether that option applies to your home.

Which panel should feed it?

If the parking space is near the ADU, feeding the charger from the ADU subpanel keeps the run short but adds to the ADU feeder load. If it's near the main house, the house panel may be simpler. Either way, the charger has to be counted in the calculation for whichever panel and service supply it.

What this means for your electrical plan

The plan should show the charger location, its rated or adjusted current, the breaker and conductor sizes, any energy management setting and the charger's line in the load calculation. See how ADU load calculations work, whether your ADU needs a panel upgrade and our electrical plans.

Sources: dpw.lacounty.gov, ecode360.com, larimer.gov, mikeholt.com, pge.com.