Glossary

Energy Management System (EMS) Term used in NEC to refer to the software controls of production sources (Solar & Battery) to maintain system limits.
Power Control System (PCS) Term used by UL 1741, NEC, and Tesla to refer to the software controls of production sources (Solar & Battery) to maintain system limits. PCS is a type of Energy Management System (EMS).
Powerwall Powerwall is a rechargeable home battery, also called a battery energy storage system (BESS). Powerwall has an integrated energy meter and performs its own battery metering.
Powerwall 3 Expansion Powerwall 3 Expansion is a rechargeable home battery that offers additional storage for Powerwall 3 systems. Expansion units must be installed with Powerwall 3, and can only be connected to each other or Powerwall 3 via the Expansion Harness. See the Powerwall 3 installation manual for more information.
Qualified Personnel A Tesla installer or Certified Installer who has the skills and knowledge related to installation and operation of electrical equipment to recognize and avoid the hazards involved.
Site Limit Prevents excess Import and/or Export through the site meter from/to the utility connection.
Conductor Limit Prevents excess current through specific monitored and controlled conductors.
Panel Limit Prevents excess current experienced by a virtual panel, fed by a sum of site, solar, and batteries.
Power/Current Limit (Powerwall 3 Only) Configures the maximum power/current output for Powerwall 3.
Grid Measured by one or more physical site meters to measure the full current flowing into the virtual panel from the grid.
Uncontrolled Sources Any equipment not connected over direct communication, including standalone solar inverters or similar sources to the virtual panel.
Controlled Sources Any equipment connected over direct communication, including Powerwall 2, Powerwall+, or Powerwall 3 in any quantity and combination (e.g. one Powerwall+ and two Powerwall 2) that can be current limited.
Virtual Panel May include several panels and conductors, and is considered as one single panel with respect to the Panel Limit feature. As there may be more than one physical panel and conductors included, the Panel Limit is set to the rating of the smallest busbar within the “Virtual Panel.”
Energy Meter Measures voltage and current to calculate net power flow. Energy meters can be of type Site, Solar, Conductor, or Load. See the Residential Energy Metering Guide for more information about meter types.
Current Transformer (CT) Installed around conductors to monitor the current flowing through them. CTs are connected to an energy meter, which uses the current measurement to calculate how much power is being produced or consumed.
Site Controller Tesla’s Site Controller is the computer that coordinates site functions like charging, discharging, self-consumption, power control, etc. All Powerwall systems have a Site Controller.
Meter X Built-in meter in the Backup Gateway 2. Its CTs cannot be relocated.
Meter Y Built-in meter in the Backup Gateway 2 with three CT terminals. Tesla CTs are installed and connected to Meter Y.
Meter Z Built-in meter in Backup Switch and Gateway 3. Its CTs cannot be relocated.
Remote Energy Meter External meters that can be installed and paired with the Site Controller for additional metering capability. Tesla Remote Energy Meter, as well as Neurio W1 and W2 meters, are supported Remote Energy Meters.