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No Solar Production During Grid Outage?

No Solar Production During Grid Outage?

I have a 12.2k system installed with 1 PW2. We recently had a mid-day grid outage that lasted about 20 minutes. During that time, I noticed that the house was properly drawing from the PW2, but I was confused to see that no power from the panels (bright sunny day) was going to the PW2.

I realize that there is a rule about solar production during a grid outage to protect the linemen, but I was told by Tesla that having the PW2 would mitigate that, and that our system could be self-sufficient if the grid went down -- meaning, 12.2k is enough to run our house for the day when the PW2 is included.

Is this normal, for there to be complete shutdown of the ability for the panels to charge the PW2 when the grid is down? That would basically make the entire system pointless during a grid outage - other than pulling from the PW2. What happens with a long-term outage? I want to be able to use the solar production in such a scenario.....

smaches | 22 August 2019

Sounds to me like everything is working as per the stated design. If your PW's are already *full* or near full, the TEG will shut down the DC path from the panels as there is no where for the excess to go. This is absolutely normal. Once the PW's hit their set point (I do not know what it is - you can call tech support if you're curious), the TEG will recharge them and again, shut off the inverter if the grid is still down.
It's like your glass of water at a restaurant. It just sits there for a while. You take a few sips and sooner or later the waiter will come along and fill it back up again.

david.morgan2 | 22 August 2019

@smaches -- thanks for the explanation. I am not certain, but I believe my PW2 at the time was at about 50-60%, so perhaps you are correct that there is a set point for charging.

Which brings up another question - if it is a bright sunny day and I am generating 9kw, is any of that energy able to go directly to the house load, or will it only charge the PW2 and all power used by the house comes from the PW2?

Tesla-David | 22 August 2019

@david.morgan2, I think @smaches stated it correctly. What was the status of your 1-PW2 at the end of the 20 minute outage, and did your solar kick back in after outage? If you are operating in self-powered mode what is your backup level set at. A 20 minute outage should have comfortably covered your home usage unless you were charging EV's or other high usage appliances. We have 13.2 kWh solar system wit 2-PW2's but have not experienced outage in past 14 months, so can't really comment on our experience. We operate in self-powered mode with backup at 20 percent. I would love to experience an outage to see how the PW2's work to cover our needs. We have done a few tests to make sure they work properly, and they operated like advertised.

smaches | 22 August 2019

For example: per the app and at this time, I am generating 2.7kW (it's only 9:40am), and my house load is pulling 0.9kW of that, with the rest being dumped to the powerwalls (I have 2). My walls are at 66% from my usage overnight and will fill to 100% by about 1 or 1:30 if I don't cook a large lunch (lol). Anyway, once full that same excess is dumped to grid.
Yes, the powerwall act like a bridge between the grid and your solar, with the house being the recipient of whatever combination is required to meet the demand (the TEG does all that magic). It is quite a balancing act, for sure....

Tesla-David | 22 August 2019

I would expect your solar would go to cover house loads, and secondarily to charge your PW2. My observations of our PW2's over past 14 months that is what I have been observing.

jrweiss98020 | 1 September 2019

My system was completed last week. While waiting for the PUD to install the Net Meter, I opened the main circuit breaker between the grid and the Backup Gateway (simulated grid outage). PV panels supplied house power and Powerwall recharge, with the house draw taking priority. When Powerwall was fully charged, PV output matched house load. Ran for 2 days like that, with 25-30% drawdown on Powerwall over night and full recharge well before noon.

After Net Meter was installed, all works well. House load, then Powerwall recharge have priority, and the rest goes to the grid. Changeover appears seamless as loads and PV output changes. 0 power bought from grid to date.

rlwrw | 3 September 2019

jrweiss98020 is correct. Panels and Powerwall are on house side of inverter. With grid down, panels are sole source of power. When Powerwall is at 100% only the house is drawing energy from the panels. Panels will still generate at their capacity for that time of the day, but the house will only draw what it needs. The rest... pffft. No place to put the excess energy. Wasted energy until the grid is back up.