Energy Products

Powerwall charging

My powerwall was installed about two weeks ago, I have been monitoring it via the app but I noticed that it has never reached a 100% charging. Is this normal?


  • It could be. It just depends on how much solar you are producing and how much your house is using at the same time. For example: If your solar system generates 20 kWh of energy for the day, and the PW starts at 0% SOC. Let's say the house uses 10 kWh from solar during the day. That leaves only 10 kWh of energy to charge the PW. The PW from 0% to 100% needs 13.5 kWh (there is some reserve, so actually a little less than 13.5 kWh). So it will be about 3 kWh short of 100%. I'd guess around 77% SOC in this example. Your app can show you your specific numbers.
  • Tesla rep told me that PW doesn't charge on solar if the grid is down. Is that true?
  • That is incorrect (and doesn't make any sense!)...

    When the Gateway detects grid power is offline, it will likely switch to only use the PowerWall power and turn off the solar panels (by setting the powerline frequency above 61 Hz). After 5 minutes, if the grid power is still off and the PowerWalls are not fully charged (below 96-97%), the powerline frequency should be set back to 60 Hz, turning on the solar panels.

    While the grid is down, the solar energy will power the house with excess charging the PowerWalls. And when the PowerWalls get close to fully charged, the Gateway will raise the powerline frequency again to turn off the solar power until the PowerWalls have drawn down some charge.

    When the grid power is restored, there will likely be a 5 minute wait before the Gateway will switch back to grid power, and resume normal operation.
  • > @ICEMELT said:
    > Tesla rep told me that PW doesn't charge on solar if the grid is down. Is that true?

    For me, the switchover is instant. I can kill my main breakers, and not miss a beat. Clocks don't reset and solar continues as normal - powering the house and/or charging the Powerwall.

    Now it may depend on your solar system. My solar roof was installed by Tesla along with the PWs and Gateway all at the same time in 2020.

    If you have a pre-existing solar system, most systems use micro-inverters on panels. These systems are designed to turn off solar in the event of a grid failure. My expectation is they would remain off even if you have Powerwalls.
  • To expand on @TeslaTap comments. I have a mixed solar (non-Tesla...all SunPower) with 70% on conventional inverter and 30% on micro inverter that was installed prior to PowerWalls. I have had 30 power interruptions since my PowerWall install. They are essentially invisible...utility drops out and I continue to have power - usually without a clue until I have a neighbor knock and ask to borrow a cup of electrons. The large inverters and microinverters all behave essentially the same during an outage. Depending on the exact inverter brand and configuration - you may experience a brief loss of solar output during a grid failure but they will come back on line to recharge your battery pretty quickly. The battery carries you thru the transition with no bumps or bruises.
  • Yes because I believe that Tesla powerwall has to take a small amount from grid just to know the grid is working and when you don't have power Tesla powerwall will quickly switch over to the battery
  • @Jones - That's great that the microinverters still operate without grid power with the Powerwalls. I wasn't sure about how that would work.
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