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Powerwall 2 Off grid clarification
- Thread starter weewards
- Start date
“Off Grid” will simulate a utility power outage by opening the grid isolation relays.
In this mode, your house will be powered by solar + batteries. When there is excess solar, it will charge your battery. If your batteries are full and there is excess solar power, they will be “curtailed” by increasing the AC frequency.
So, to answer your question, Solar would charge your Powerwalls. As long as there excess solar power.
Your logic is incorrect, at least as it pertains to the solar + battery installs. The point of going "off grid" is to make your home a micro grid, and that includes solar + batteries.
For the rest of the answer I will just +1 what @lodar said.
aesculus
Still Trying to Figure This All Out
One tiny exception. For those of us who have some circuits outside of the Powerwall Gateway (my TWC for example), these would still be available during a simulated grid outage, but backed up circuits and the Powerwalls would be as described above.
I dont actually consider the off grid in the app to be really "off grid, for realsies" because of that reason.
LOL! I carefully used the term “simulates” to soften the claim
“Go Off-Grid” also doesn’t generate the nasty power transients that reboot or fry unprotected electronics that folks often think the Powerwalls would protect from.
I see, I was taking it literally that the Tesla essentially isolated itself but I can see now how the solar panels are still able to charge the Powewall, thank you.
FWIW A friend uses the Off Grid mode simply to stop exporting any solar power when his battery is full as he doesn't have an export tariff with his power utility provider.
In that case, if your friends batteries are full when thy push the off grid button, it would shut off the solar panels (because the power has no where to go). Once the batteries drain "some amount" (which appears to be configurable by Tesla / Installers per system), the PV system would turn back on and start filling the batteries again.
The Grid Isolation Relay is a mechanical device which was meant to toggle in the unlikely event of a power outage. Not sure how much Tesla has over or under engineered it for daily cycling to micromanage exports
I feel that there must be a smarter way to do this.
Is your friend trying to avoid an export penalty, or are they just trying to “stick it to The Man”?
The Grid Isolation Relay is a mechanical device which was meant to toggle in the unlikely event of a power outage. Not sure how much Tesla has over or under engineered it for daily cycling to micromanage exports
I feel that there must be a smarter way to do this.
Is your friend trying to avoid an export penalty, or are they just trying to “stick it to The Man”?
The system can be configured by Tesla for "no export" I am almost positive. I think its just a grid profile but I am not an expert by any means on this topic, but I think a lot of people in Hawaii (for example) are not allowed to export so their systems are setup that way. I know its possible, just not sure whats involved, and setting it up that way means they would never export.
They would lose control over whether they could or couldnt export if they set it up that way, but its possible if they want to pursue it I am sure.
Interesting, back to my original query, maybe I should have phrased it better & included the details about a lack of export Tariff but maybe I was right overall???
So is the result the same whether you press off grid or not if the batteries are full, the house needs are met by solar and you dont have an export tariff are the solar panels switched off until the there is somewhere for the solar energy to go?
Matt-FL
Member
I imagine that even if you don't get credit for sending power back to the grid, it may be better to send it anyways instead of sending freq changes and shutting down the inverters several times during the day. Maybe I'm just timid about forcing something to shut down. Then there's the case that it might shut down towards the end of the day, drain some batteries, and when they drain enough, -- no more sun.
Can anyone comment on whether forcing shutdowns is tougher on the equipment than just letting it run and export?
Can anyone comment on whether forcing shutdowns is tougher on the equipment than just letting it run and export?
No, tariffs alone will not curtail solar production. Tariffs control Time-Based Control operation, which optimizes for savings. Solar curtailment is not part of that process, you'd have to go off-grid for that. Another possibility (which I haven't tested): if you have the option, you can set your Permission to Export to No. This might be a lighter-weight approach to avoiding exports.
There's one scenario where you'd want to stop exporting altogether: negative feed-in tariffs, where you get charged for exports. These might happen for utilities with real-time pricing. One such example is Amber Electric in Australia, and they recommend going off-grid and document the caveats associated: Offgrid mode for Tesla customers.
I think they are as you say trying to "stick it to the man", personally IF i was in his position I would have the attitude that as my batteries were full & my house had all the power it needed then any excess should go back to the grid and if it helps in any way to alleviate the need to spin up another fossil burning power station then I would be happy with that. I also have an issue that trying to lose power/energy cant be good for the quipment anyway.The Grid Isolation Relay is a mechanical device which was meant to toggle in the unlikely event of a power outage. Not sure how much Tesla has over or under engineered it for daily cycling to micromanage exports
I feel that there must be a smarter way to do this.
Is your friend trying to avoid an export penalty, or are they just trying to “stick it to The Man”?
The accurate way to describe the situation is that the batteries will power the house and the solar will remain shut down until there is some buffer in the battery to allow battery charging from solar. When the battery gets full again, the Powerwalls will raise the frequency and the solar will shut down again. If your solar is configured to respond to small frequency shifts, the solar will remain online and will curtail according to the frequency set by the Powerwalls.
There is a difference in this statement and what you originally said. "Switched off until there is somewhere for the solar energy to go (the batteries drain some)" is not the same as "solar doesnt charge powerwalls". So, no, your original statement wasnt correct, as solar does charge the powerwalls when they drain some.
Hi Thanks for you reply, I am not sure I used the words switched off myself and i dont really mind if I was right or wrong but I do want to understand the process. Other replies here seem to indicate that when the "go off grid button" is pressed solar will charge the batteries until full but will then turn off the solar panels until needed whereas in normal conditions without the button being pressed, if the batteries are full the frequency is changed and the solar panels might be shut down until needed.
No. In normal conditions when the system is totally grid interactive, the solar will simply be exported when it exceeds the home consumption and the batteries are full. The system can only change the frequency when off grid.
Solar will only be curtailed (reduced or shut off) in two conditions:
- When the system is running off grid and there is nowhere for the solar production to go.
- Your system is grid interconnected, but not allowed to export. This can be before you have Permission to Operate, or it can be part of the interconnection agreement. Automatic curtailment to prevent export can be accomplished with Tesla solar inverters or third party inverters that independently measure the grid flow and curtail their own output independently from the Powerwalls. When Powerwall batteries are charging from solar in this situation, it looks like household load to the solar controller.
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