Very slow switch to Backup + Solar

Very slow switch to Backup + Solar

I know that generally solar panels are turned off when there is a power outage due to the need preventing electrocuting utility workers. However, with the Tesla PW2 installed, we are cut off from main and the solar panels are still operational feeding into the PW2; and of course, we can use power stored in the PW2 as backup during the power outage.

Today, we have experienced a planned power outage and tried this the first time: ON the day prior we switched to "Backup Only" mode 100%. The grid turned off and the PW2 jumped on perfectly—we did not even notice.

HOWEVER, the solar panels first did not feed any energy into the house or the draining PW2 according to the app. After about 30 min they kicked in and started feeding into the PW2 and the house.

Note: There was plenty of sunshine (as usual in Sydney I might add)!

Any reason for this delay?


cwied | July 5, 2018

When you're disconnected from the grid, there's nowhere for solar energy to go except to your house and the Powerwall. This means the Powerwall needs to have room for the excess solar that your house isn't using. The Powerwall adjusts the frequency of the electricity to get the solar inverter to turn off until there's room to absorb any excess.

There's probably no reason to switch to backup-only mode if you have sufficient solar production during a planned power outage. As long as you set a reasonable reserve, the solar will fill up your Powerwalls with the excess production. I have my reserve set to 40% and in a recent unplanned power outage my Powerwalls (I have 2) filled up to 95% by the end of the day.

heiko | July 5, 2018

Ah, makes sense. Thanks!