Backup power mode, called Backup-Only in the Tesla app, reserves 100% of your Powerwall energy to provide seamless power to your home in the event of an outage. Powerwall will charge from the grid (if you don’t have solar) or from your solar system and only discharge during a grid outage.
How Powerwall Provides Backup Power
When a utility power outage does occur, your Powerwall instantly disconnects from the grid and restores backup power to your home, much faster than typical standby generators. Most customers won’t even notice when an outage occurs.
Depending on the inverter, your Powerwall can recharge from your solar system, even during backup mode, so you can run your home from solar and Powerwall indefinitely. A traditional solar system without a Powerwall does not function during a grid outage but Powerwall enables your solar system to continue producing power when the grid is down.
If more solar energy is being produced than can be used or stored during an outage, Powerwall will turn off the solar system and turn it back on when the energy can be used again.
Tips for Living With Powerwall During an Outage
Lowering energy use during an outage will extend the amount of time your Powerwall will be able to provide power. The best way to do this is to limit use of non-essential or energy-intensive appliances like dishwashers, washing machines and electric heaters.
If you lose the ability to monitor your system in the Tesla app due to internet and mobile phone masts being down, monitor your system locally.
During an outage, vehicle charging is not recommended. Vehicle charging will quickly deplete Powerwall. If you must charge your vehicle at home during an outage, it would be best to limit the amount and do so when the sun is shining.
Powerwall at Low Charge
If solar is not available during a long outage due to bad weather or because you do not have solar, there is a chance your Powerwall could become depleted during an extended outage. Powerwall will turn off when it gets to a low charge to avoid becoming completely empty.
If you have a solar system, Powerwall will turn on during daytime hours to check for solar every hour for a few minutes. If Powerwall sees solar, it will charge from it. If Powerwall does not see solar, it will shut back down to conserve energy. If Powerwall has been unsuccessful at restarting solar after multiple attempts, it will cease trying to further conserve energy.
You can manually force Powerwall to restart solar by toggling the enable switch on the side of Powerwall. It is best to do this in the daytime after turning off as many home loads as possible and letting Powerwall charge up past 15% before resuming normal usage.
How to set up Backup-Only
Backup Power Notifications
If the grid has been unavailable for at least five minutes, the Tesla app will send you an alert so you can manage energy usage accordingly. A second notification will be sent once power has been restored. To ensure you receive this alert, go to ‘Settings’ and select ‘Notifications’ in the Tesla app. Here you can set preferences for receiving all notifications, including Power Outages. Ensure that your device settings allow notifications from the Tesla app.
From the home screen, tap 'Customize.'
Select Backup-Only mode.