Tesla adds a ‘Charge on Solar’ feature to its Powerwall batteries

Tesla announced it has added a new Charge on Solar feature to its Powerwall app, enabling automatic charging of vehicles only on battery-stored solar generation. Using the app, Tesla drivers can ensure their vehicle is fully powered by local, emissions-free electricity. 

Following a few simple prompts, users can set charge limits and locations, charging the battery to a predefined level while relying only on electricity produced by the homeowner’s rooftop solar array. The app will enable the vehicle to adjust charge power approximately every 10 seconds to match the excess solar power and power consumption elsewhere in the home. Tesla vehicle may delay the start of  

The battery will delay charging until there is at least 1.2 kW of stable excess solar to maximize efficiency and lifetime of the charging equipment. This helps account for variability in solar power and home loads. 

The Charge on Solar feature is compatible with existing Powerwall battery charge schedules including: 

• Storm Watch
  Powerwall will prioritize charging from any source to prepare for an outage during severe weather events before allocating any excess solar power for vehicle charging. 
• Backup Reserve
  If the Powerwall’s stored energy is below the backup reserve, it will prioritize charging to the set backup reserve percentage before allocating any excess solar power for vehicle charging. 
• Self-Powered
  Powerwall will allow the Tesla vehicle to charge on excess solar until the set charge limit, while covering changes in home loads and solar production until the vehicle adjusts its charging power. Once the vehicle has met its charging limit, the Powerwall will charge on excess solar as usual. This is the recommended mode to maximize Charge on Solar operation with the vehicle.
• Time-Based Control
  The battery stores energy when energy costs are low and may sell that low-cost energy back to the grid when energy costs are higher, instead of using the excess solar energy for Charge on Solar. This also enables participation in virtual power plant or utility program events. In most cases, the vehicle will pause charging during peak to prioritize total savings or charge the Powerwall from excess solar, while charging your vehicle during off-peak from the grid.
• Go Off-Grid
  When the battery is off-grid, the Tesla vehicle will continue to charge on excess solar unless Powerwall prioritizes saving energy for home use during the outage.

Charge on Solar is currently only available to customers who own a Powerwall and a Tesla vehicle in the U.S. and Canada.