Powerwall 3 performs Rapid Shutdown (RSD) in compliance with NEC 2017, 2020, and 2023 690.12(B)(2) and 690.12(B)(1) and UL1741 standards to reduce shock hazard for emergency responders. To meet these RSD requirements, Tesla Mid-Circuit Interrupters (MCIs) must be installed within PV strings and arrays. For technical details and installation requirements for the Tesla MCI, see the Powerwall 3 installation manual.

To calculate how many MCIs are required for PV array based on the inside-the-array boundary voltage limit, see the UL 3741 Application Addendum. Tesla does not assist with these calculations; it is the sole responsibility of the Certified Installer to maintain code compliance.