Energy Metering

Power measurements are needed for Powerwall 3 system to operate properly, and for system data to appear in the customer's Tesla app. An energy meter accomplishes this by measuring voltage (by voltage tap) and current (by Current Transformer, or CT) at key locations in the system.

CTs are installed around conductors to monitor the current flowing through them. The CTs are connected to a meter which sends the measurements to Powerwall 3. Using this current measurement, the system calculates power measurements to determine how much power the customer is using, or how much power the PV system is producing. The power values are then displayed in the customer's Tesla app and are used by the system to operate as configured by the customer. For instance, a customer may want to store their solar power for use at night. CTs measure both solar production and the home's power consumption so that the system knows how much solar to store during the day and supply at night.

There are many possible configurations for installing metering depending on system design. However, there are two goals, site metering and solar metering.

Site Metering: Site meters show the overall power flow to/from a site from the Grid’s perspective, i.e. the Grid is treated as the source of power and the home is a consumer of that power. Site meter(s) must be installed upstream of all solar production, Powerwalls, and home loads.
Solar Metering: Solar meters capture production from solar inverter(s). There must not be any loads or Powerwalls behind the Solar CTs. This would result in under- or over-estimation of solar production.

Metering Options


Meter	Backup Gateway 2 Primary Meter X	Backup Gateway 2 Secondary Meter Y	Tesla Remote Energy Meter
Meter	Figure 1. Backup Gateway 2 internal meters		Figure 2. Tesla Remote Energy Meter CT terminals Note CT4 functionality will be available at a later date.
Compatible CTs	Not applicable (Primary Meter X has three integrated CTs)	Up to three Tesla 100A CTs (one per phase). For full specifications, see Tesla 100A CT Specifications. Note One CT is included in the accessory kit; additional CTs can be ordered individually.	Up to three Tesla 200A CTs (one per phase). For full specifications, see Tesla 200A CT Specifications. Note One CT is included in the kit; additional CTs can be ordered individually.
CT Capacity	80 A per phase / 100 A if using only one phase	100 A	200 A
Supported Locations	Site, Conductor, None	Site, Solar, Generator, Conductor, None	Site, Solar, Generator, Conductor

See Specifications for full specifications of the meters and CTs.

Primary Meter X can be used for measuring the site when the Grid connection is at the Supply terminals on Backup Gateway 2.
Figure 3. Example Whole Home Backup Metering Diagram: Meter X Measures Site
Figure 4. Example Partial Home Backup Metering Diagram: Meter X Measures Site
Note
In this configuration, the non-essential loads are downstream of Backup Gateway 2 (i.e., they are connected to the Non-Backup terminals on Backup Gateway 2).
Secondary Meter Y: When there are loads upstream of Backup Gateway 2 or the system includes AC-coupled solar, Tesla 100A CTs can be installed and connected to the Meter Y CT terminals for measuring the site or solar.
Figure 5. Example Partial Home Backup Metering Diagram: Meter Y Measures Site (Meter X Configured as None).
Figure 6. Example Partial Home Backup Metering Diagram: Meter X and Meter Y Measures Site
Figure 7. Example Partial Home Backup Metering Diagram: Meter X Measures Site and Meter Y Measures AC-Coupled Solar
Note
Meter Y can only measure the site or the AC-coupled solar, not both.
CAUTION
If AC-coupled solar is not metered correctly, Powerwall will not frequency shift to control solar during a grid outage, resulting in a serious risk of damage to the customer's home loads and/or Powerwall.
Tesla Remote Energy Meter : When there are loads upstream of Backup Gateway 2 and the system also includes AC-coupled solar, Tesla 200A CTs can be installed and connected to the Tesla Remote Energy Meter CT terminals for measuring the site or the AC-coupled solar.
Figure 8. Example Partial Home Backup Metering Diagram: Tesla Remote Energy Meter Measures Site and Meter Y Measures AC-Coupled Solar (Meter X Configured as None)
Figure 9. Example Partial Home Backup Metering Diagram: Meter Y Measures Site and Tesla Remote Energy Meter Measures AC-Coupled Solar (Meter X Configured as None)
Figure 10. Example Partial Home Backup Metering Diagram: Tesla Remote Energy Meters Measuring Site and AC-Coupled Solar (Meter X and Y Configured as None)
Powerwall 3 measures its own solar (i.e., DC-coupled solar). No additional meter needs to be installed or configured for Powerwall 3.
Note
Powerwall 3 is not compatible with Neurio remote energy meters.
Note
Powerwall 3 has an internal battery meter which will not be called out in this document, as is not installed or configured by the installer.