Visibility on power and energy data is needed for the Powerwall+ system to operate properly. An energy meter accomplishes this by measuring voltage (by voltage tap) and current (by Current Transformer, CT) at certain points in the system.

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

• Metering the Site – Site meters show the overall power flow to/from a site from the Grid’s perspective. Thus, Site meter(s) must be installed upstream of all solar production, Powerwalls, and loads. Multiple physical Site meters can be installed together where needed, but their sum should capture all of the power flows from load, solar, and Powerwall(s).
• Metering all Solar – Solar meters capture production from PV 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.