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 your solar system and only discharge during a grid outage.
Backup-Only mode behaves similarly to setting your Powerwall in Self-Powered mode with a 100% backup reserve.
During a power outage, you might consider adjusting some behaviors to extend your use of Powerwall. Read more about life with Powerwall during an extended outage.
How to set up Backup-Only
From the home screen, tap 'Customize.'
Select Backup-Only mode.