Solar + Powerwall: Sell solar to grid, use Powerwall for sundown peaks, charge at night?

[Hurin]

Hi All,

I've seen a lot of discussions about charging your powerwall during off-peak hours. I'm wondering just how much this can be fine-tuned?

Is this possible:

• Near-Peak and Peak Hours (sun up) 7am to 6pm: Sell excess solar to grid. Powerwalls inactive (not charging or powering anything).
• Peak Hours (no sun) 6pm to 9pm: Solar inactive. Powerwalls are powering household. No grid usage.
• Near-Peak Hours (no sun) 9pm to 11pm: Solar inactive. Powerwalls are powering household.
• Off-Peak Hours (no sun) 11pm to 7am: Solar inactive. Grid is powering household, charging car, and charging powerwalls.

Right now, I have only solar. And I bought/installed a few years ago where (due to NEM 2.0) the utility really wouldn't let us "buy as much solar" as we wanted. While grandfathered in to NEM 2.0, I don't think powerwalls really make sense from a financial perspective, unless something like the above is possible.

Best Regards,

H

P.S. I realize the plan above isn't the green-conscious option. And it's only one plan I'm considering (another being adding many panels and some powerwalls, foregoing NEM 2.0, and being entirely self-sufficient). I'd like to consider this strictly from a financial perspective rather than from an environmental/ethical perspective if everyone's willing to withhold judgement momentarily.

 

[ucmndd]

Yes it’s possible, and furthermore it’s exactly what I do using the Time Based Control and Grid Charging features of the powerwall on the PG&E EV-A plan under NEM2.

I also use the “Export Everything” setting to send all of my excess powerwall energy back to the grid during peak time for credits, assuming there’s some left after powering my home’s needs.

 

[Hurin]

Interesting! Thank you!

I'm seeing some reports of PG&E customers (like me) seeing "PAIRED STORAGE: MAXIMUM EXPORT ESTIMATION" on their bill which would seem to be PG&E's attempt at limiting just how much they'll allow a customer to export back to them?

Question for PG&E folks out there, should I assume that I too will have this limit placed on my account when I add the powerwalls?

 

[lucos71]

I've just been trying to figure all this out myself. On the phone with PG&E for a long time. They were helpful but not the entire story. What I think is true is that you can only export what your generate from Solar production. So say there is zero solar production but your battery is full and you export 50% of it to the grid. Apparently you won't get credit for this. My recent statement showed 1161 kw used, 1056 kw exported to grid, maximum PV generation 644 kw. So because I went over the maximum i only got the maximum credit of 644. And it appears that the way they credit your usage is to apply the credit first to energy used during off peak, then to part peak then to peak. In my situation I got full credit for my 570kw off peak usage, partial for my part peak and no offset for my peak usage. Arg! The PV maximum credit per month is based on a national average and not your actual production. The PV maximums per month vary by month from 386kw in Dec to 930kw in July. So you can send energy to the grid from you powerwall but don't send more than the max PV for that month. Anyway I'm still figuring this out. Would love to hear from someone who has this nailed.

 

[Eveque Fou]

Not a PG&E customer, but here's my understanding from another thread. When your system was installed, they got data that they use to calculate your expected solar production each month. They won't allow you to export more than that. However, it doesn't matter if what you export is coming directly from solar in that moment, or solar-charged batteries, or even (arguably) grid-charged batteries when your solar went to supply actual usage.

You're allowed to use the batteries to shift your load and production to any time period you like, you just can't export more than you could actually have produced.

 

[QtownTaxiGreg]

Not a PG&E customer, but here's my understanding from another thread. When your system was installed, they got data that they use to calculate your expected solar production each month. They won't allow you to export more than that. However, it doesn't matter if what you export is coming directly from solar in that moment, or solar-charged batteries, or even (arguably) grid-charged batteries when your solar went to supply actual usage.

You're allowed to use the batteries to shift your load and production to any time period you like, you just can't export more than you could actually have produced.

Does that mean he's getting 100% kWh per kWh credit on what he sends to the grid?

I'm not seeing an angle.

If you send solar to grid in peak demand you aren't charging the powerwall but you are helping out the grid.

If you use your solar in peak time you are helping out the grid.

Those are the only 2 options when the sun is shining, right?

If.you send so much juice away during the sunny day that your wall doesn't charge enough to supply the darker hours you buy power at the applicable rate which would be less than the peak rate most of the time?

Everyone's a winner?

 

[Eric99]

I had my trueup a few months ago. I am a net producer by a good amount and was surprised that my trueup was $300. I was using time based control and exporting at 3pm and using PWs til midnight, then charging the ev and running dishwasher/ clothes dryer from grid. I was exporting a lot to the grid but using a lot of grid at a “cheaper” rate. The $300 trueup came from all the NBCs of $.03/kWh.

I now am using self powered and draw zero from the grid (since march). I believe this is the way to go if you are a net producer and have NBCs.