Plenty of solar to cover house and charge PW - but still pulls from grid - Why?

[Steve2498]

I'm in Time Based Control mode, Battery at 85% and charging with excess solar. Batteries will get to 100% in less than 2 hours based on current production. Most of the time it is not drawing from the grid, but periodically it starts drawing ~.2kW - ~.4kWs from the grid for 20 - 30 seconds, then goes back to drawing 0kW.

Does anyone understand this behavior?

Thanks

 

[jboy210]

I always guessed the GW was just checking to make sure the grid was there and working as expected. My system does this for 10-15 seconds every 15 minutes or so when the Powerwall reaches 100% and switches to sending the excess to the grid.

 

[Steve2498]

That sounds like a reasonable guess

 

[aesculus]

I always assumed this was some sort of rounding error in the CT math. The question is at the end of the day, how much grid power did it say you used? If it adds up to a few hundred Watts then maybe it is pulling from the grid occasionally (assuming you are 100% solar energy fulfilled). If less than a 100 Watts at the end of the day I would not even sweat it.

Note I am no where near solar break even, but when I am I occasionally see .1 of a kW come and go across various feeds.

 

[ptdusn]

@jboy210 My system is set for Self-Consumption and it does the same thing, Pulling .1-.2kW every now and again. Your reason could be plausable.

 

[slcasner]

@jboy210 My system is set for Self-Consumption and it does the same thing, Pulling .1-.2kW every now and again. Your reason could be plausable.

As the solar output and the house load vary, the Powerwalls need to adjust their charge/discharge rate to keep the net load matching the solar output for non-export (Self-Consumption) mode. That adjustment can't be instantaneous, so there is likely to be a small amount of energy going to or from the grid.

 

[George75]

My system is doing the exact same crap. I'm set to self powered, 7.2kw panels with one PW+ just installed a month ago.

Every other second it pulls about 0.1kw then stops and starts. It does this all day in the end it'll pull about 2kw total. However it stops this when the solar isn't producing anymore. It also stops this if I set PTO from the app to No. It does this again when I set PTO to Yes in the app. I have PTO from my utility.

I've opened a ticket with Tesla but I'm trying to figure out why this is. I can't imagine this is by design or normal behavior. For every kw my system wastes on this I have to generate another 2kw just to break even with my utility. They don't do 1 for 1. They only pay wholesale rates which are low.

Right now it's early morning I'm generating 4kw and I've 60% on my PW yet it's pulling 0.1kw from the grid