Overview

Powerwall is managed by a software platform that allows the system to provide grid services, economic returns, and energy security while maintaining system limits. System limits can vary depending on the connection of the Powerwall, the electrical infrastructure on site, and the interconnection of the system.

Power Control System (PCS) is a type of Energy Management System (EMS) and is a term used by UL 1741, NEC, and Tesla to refer to software controls of production sources (Solar & Battery) to maintain system limits. PCS software can limit the power of a Powerwall system to safely interconnect with a variety of home electrical system ratings. As a result, PCS can help avoid expensive electrical upgrades, complicated load relocation, or a reduction in system performance.

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Note
PCS features are on-grid controls; controls such as frequency shifting are only available during a grid outage and are not considered part of PCS, and as such are not part of the scope of this document.

UL1741 CRD for PCS and NEC 705.13 (introduced in 2020 revision) outline a variety of requirements that a system must provide to be qualified as a Power Control System (PCS). Tesla has implemented software in accordance with these standards. PCS is implemented after review of system risks to ensure that the PCS controls, when combined with traditional design methodology and overcurrent protection, will ensure safe and effective system operation. Tesla has reviewed the behavior of all parts of the system to ensure a proper response even during a loss of communication or a hardware failure.

Power Control System (PCS) methodology and implementation can be used to manage a system to enforce the following limits:

  • Site Limit: To prevent excess Import/Export through the site meter to/from the utility connection
  • Conductor Limit: To prevent excess current through specific monitored and controlled conductors
  • Panel Limit: To prevent excess current experienced by a virtual panel, fed by a sum of site, solar, and batteries
  • Power / Current Limit (Powerwall 3 only): To limit the power and current output of Powerwall 3
Informational PurposesAn informational icon, calling your attention
Note
Site, Conductor, Panel, and Power / Current Limits are all types of PCS. These terms are distinct and specific features of Tesla’s overall suite of PCS controls.

Tesla and a Nationally Recognized Testing Laboratory (NRTL) have certified the Power Control System implementation for all three of these features to standards set forth in UL1741-CRD-PCS for 240V split-phase grid services up to 200A with Backup Switch, Backup Gateway 2, or Gateway 3.

For installations in accordance with NEC 2020 or newer, this document can be shared alongside the relevant NRTL-certified PCS VoC (available on Partner Portal) to the appropriate AHJ (Authority Having Jurisdiction) to support the inspection, permitting, and interconnection process.