Time of Use Power Shifting for Powerwall 2

[cwied]

Can you automate this like run a Raspberry Pi to call the PW API at the desired times of the day?

This would give us TOU-time-shifting without waiting for Tesla.

You definitely could automate this on a raspberry Pi (or any computer that runs all the time). In fact, since the requests are made to Tesla's servers, not to the Powerwall locally, you could probably build an automated solution using the IFTTT maker channel and AWS Lambda. Once I get my Powerwalls next week, I might give it a shot.

The part that's missing for me is charging from the grid and/or being able to offset the house load while exporting to the grid during peak hours. I'm on the E6 rate plan and I have a south-west facing array, so I don't really care to charge at partial-peak in the morning just to discharge at partial-peak in the afternoon.

 

[NuShrike]

The part that's missing for me is charging from the grid and/or being able to offset the house load while exporting to the grid during peak hours. I'm on the E6 rate plan and I have a south-west facing array, so I don't really care to charge at partial-peak in the morning just to discharge at partial-peak in the afternoon.

I expect this part boils down to just changing the reserve-level, and/or changing the mode between self-consumption or backup.

 

[cwied]

I expect this part boils down to just changing the reserve-level, and/or changing the mode between self-consumption or backup.

One problem is that according to Tesla a Powerwall installed with a PV system will only charge from solar, not from the grid. The other problem is that during the peak period the Powerwall won't discharge to offset the house load because the net flow is to the grid, not from the grid. Instead, it'll try to charge itself. As I understand the self-consumption mode, it will only reduce the grid consumption to zero, it won't make it more negative.

 

[miimura]

One problem is that according to Tesla a Powerwall installed with a PV system will only charge from solar, not from the grid. The other problem is that during the peak period the Powerwall won't discharge to offset the house load because the net flow is to the grid, not from the grid. Instead, it'll try to charge itself. As I understand the self-consumption mode, it will only reduce the grid consumption to zero, it won't make it more negative.

1. A PW2 with solar will only charge from solar. You can see that in my chart above.
2. If you have solar production during Peak hours and the PW2 is capable of absorbing it all, it will do that. There will be no solar export until the battery is full.

#2 above is why I want to avoid PW discharge during Off-Peak. You're losing money to negative arbitrage because the solar was generated during Part-Peak and you're using it during Off-Peak. That's a losing proposition. If you avoid Off-Peak discharge, then the battery will be full earlier in the afternoon so that you can earn Peak credits. Those credits will only be the excess from your household consumption. In theory, Tesla could allow PW discharge during the Peak period to match your household consumption and allow the solar to ALL go to the grid and earn credits. However, I don't really expect them to do that even though there is probably no regulatory reason they couldn't, even with a non-export interconnect agreement.

 

[Frankman60]

Thanks for that explanation. If I understand you correctly, your best scenario given the the current PW capabilities is to not import any power from the grid during peak hours. And that would mean that the combination of PW energy and solar energy must at least equal the house consumption during the peak period. So the charge level of the PW batteries when the peak period begins is an important part of that equation. While I am waiting for 2 PWs to be installed, I have been trying to determine if I can accomplish this by simply setting the reserve to the right level rather than manually switching to/from backup and self-consumption modes. Because my peak period doesn’t begin until 4 PM, there are more daylight hours to recharge the PWs. I am hoping that eventually Tesla will allow the PWs to be programmed to drain down during the peak period so surplus solar could be exported to the grid. This would involve changing the priority of how solar energy is used. I believe in self-sustaining mode sufficient solar energy goes first to house consumption, PW battery charging until full, and then to the grid in that order. During peak hours, I would like the order to be house consumption, and then excess to the grid (not charging the PWs). If solar energy is not sufficient to cover house consumption during peak, draw from the PW until it gets down to the reserve level, but continue exporting solar to the grid. Is this possible given the way that the hardware works?

1. A PW2 with solar will only charge from solar. You can see that in my chart above.
2. If you have solar production during Peak hours and the PW2 is capable of absorbing it all, it will do that. There will be no solar export until the battery is full.

#2 above is why I want to avoid PW discharge during Off-Peak. You're losing money to negative arbitrage because the solar was generated during Part-Peak and you're using it during Off-Peak. That's a losing proposition. If you avoid Off-Peak discharge, then the battery will be full earlier in the afternoon so that you can earn Peak credits. Those credits will only be the excess from your household consumption. In theory, Tesla could allow PW discharge during the Peak period to match your household consumption and allow the solar to ALL go to the grid and earn credits. However, I don't really expect them to do that even though there is probably no regulatory reason they couldn't, even with a non-export interconnect agreement.

 

[cwied]

During peak hours, I would like the order to be house consumption, and then excess to the grid (not charging the PWs). If solar energy is not sufficient to cover house consumption during peak, draw from the PW until it gets down to the reserve level, but continue exporting solar to the grid. Is this possible given the way that the hardware works?

It's not a hardware issue, but a firmware issue, but this is exactly what's missing from my scenario. There is no way to prioritize house load over charging the Powerwalls with the current firmware. If you set to self-consumption mode, it will charge the Powerwall rather than exporting to the grid. If you set it to back-up mode, it won't do anything, and solar will go to cover the house load.

 

[eml2]

It's not a hardware issue, but a firmware issue, but this is exactly what's missing from my scenario. There is no way to prioritize house load over charging the Powerwalls with the current firmware. If you set to self-consumption mode, it will charge the Powerwall rather than exporting to the grid. If you set it to back-up mode, it won't do anything, and solar will go to cover the house load.

I don't think it needs any prioritization. All it needs is to add a scheduling scheme for when PW is allowed to be charged. Just set it not to be charged during peak.

 

[KJD]

Well, supposedly, TOU shifting will be available "shortly". Idk about SoCal but when I lived on PG&E territory, it would have been nice to fill a PW at off-peak and use it during peak. I'd wait to see how the software pans out.

So in Tesla Time that could be tomorrow or any day in the next 5 years right ?

 

[Frankman60]

I agree. That would solve the problem.

I don't think it needs any prioritization. All it needs is to add a scheduling scheme for when PW is allowed to be charged. Just set it not to be charged during peak.

 

[cwied]

I don't think it needs any prioritization. All it needs is to add a scheduling scheme for when PW is allowed to be charged. Just set it not to be charged during peak.

That's already supported - just turn it to backup mode. The key is I want it to discharge during peak. As I understand it there are regulations prohibiting exporting power from the Powerwall to the grid, but I would think that covering the house load from battery while exporting all of the solar power should be ok.

Edit: just to clarify - my peak is 1pm to 7pm, so I'm usually a net exporter for the entire peak period during the summer.

 

[eml2]

That's already supported - just turn it to backup mode. The key is I want it to discharge during peak. As I understand it there are regulations prohibiting exporting power from the Powerwall to the grid, but I would think that covering the house load from battery while exporting all of the solar power should be ok.

Edit: just to clarify - my peak is 1pm to 7pm, so I'm usually a net exporter for the entire peak period during the summer.

Turning it to backup mode will make PW charged at max rate of 1.7 kW per PW from solar. Any excess solar will use up by the house, the rest export to grid. I thought this is not what you want. You want it not to be charged during peak.

I don't think the key is to discharge during peak. The key is to discharge to cover the house load and minimize import from grid, which it is already doing it now. If you only want it to discharge during peak, then you don't want to discharge during off-peak, and instead use the grid? Remember that if you have solar, you can't charge it using the grid.

Also, electrons from PV panels or PW looks the same to the grid, meaning the grid can't tell if the export power is coming from solar or PW. The gateway cannot export all the power from solar to grid while discharging your PW to cover house load. All it can do is minimize grid import.

 

[cwied]

I don't think the key is to discharge during peak. The key is to discharge to cover the house load and minimize import from grid, which it is already doing it now. If you only want it to discharge during peak, then you don't want to discharge during off-peak, and instead use the grid? Remember that if you have solar, you can't charge it using the grid.

Also, electrons from PV panels or PW looks the same to the grid, meaning the grid can't tell if the export power is coming from solar or PW. The gateway cannot export all the power from solar to grid while discharging your PW to cover house load. All it can do is minimize grid import.

I think maybe I wasn't clear enough about my goals. My goal in buying the Powerwalls is ultimately backup and TOU load shifting to take advantage of the cheapest grid power. So the answer is correct, I don't care to discharge during off-peak. Ideally I would also like to charge from the grid, but I do understand that that isn't currently allowed, even if I'm not taking the ITC.

I also understand that the electricity is fungible, but I have an interconnection agreement for my solar system that allows me to export any electricity the solar panels produce to the grid. I figure adding the Powerwalls is the same thing as shutting off my house load, and I should be allowed to export up to my total solar production to the grid. The gateway is measuring both house load and solar production, so it certainly has all the data necessary to figure out what that amount is. Where the actual electrons come from is irrelevant - it's only the amount of energy that flows through the meter that matters.

What I'm hoping will eventually happen is that there will be a real-time rate option available from PG&E where the current rates determine whether I charge or discharge the batteries. I know this is years (maybe decades) off, but it seems to me there's no reason distributed Powerwalls couldn't perform the same grid-stabilizing function the Powerpacks are doing in Southern Australia.

 

[eml2]

I think maybe I wasn't clear enough about my goals. My goal in buying the Powerwalls is ultimately backup and TOU load shifting to take advantage of the cheapest grid power. So the answer is correct, I don't care to discharge during off-peak. Ideally I would also like to charge from the grid, but I do understand that that isn't currently allowed, even if I'm not taking the ITC.

I also understand that the electricity is fungible, but I have an interconnection agreement for my solar system that allows me to export any electricity the solar panels produce to the grid. I figure adding the Powerwalls is the same thing as shutting off my house load, and I should be allowed to export up to my total solar production to the grid. The gateway is measuring both house load and solar production, so it certainly has all the data necessary to figure out what that amount is. Where the actual electrons come from is irrelevant - it's only the amount of energy that flows through the meter that matters.

What I'm hoping will eventually happen is that there will be a real-time rate option available from PG&E where the current rates determine whether I charge or discharge the batteries. I know this is years (maybe decades) off, but it seems to me there's no reason distributed Powerwalls couldn't perform the same grid-stabilizing function the Powerpacks are doing in Southern Australia.

All I am saying is that probably all we need is TOU for charging PW, no need for TOU for discharging. And if the new TOU feature is only dealing with charging, does the interconnection agreement still come into play? If not, then the TOU feature is only a software change, no need to get any agreement with POCO.

 

[cwied]

All I am saying is that probably all we need is TOU for charging PW, no need for TOU for discharging. And if the new TOU feature is only dealing with charging, does the interconnection agreement still come into play? If not, then the TOU feature is only a software change, no need to get any agreement with POCO.

Fair enough. I was under the impression that the correct combination of mode and reserve would make the powerwalls not charge even when the solar is producing. If that's not possible, then that would be a minimum first step. My install is next Thursday/Friday, so hopefully I can start playing with it after that.

 

[NuShrike]

All I am saying is that probably all we need is TOU for charging PW, no need for TOU for discharging. And if the new TOU feature is only dealing with charging, does the interconnection agreement still come into play? If not, then the TOU feature is only a software change, no need to get any agreement with POCO.

No, I need TOU support to prevent discharging during off-peak. I do not want to use expensive TOU solar electrons when grid electrons are cheaper.

I'm fine with PW charging in early morning because of ITC, but the important part is controlling PW's SoC level during peak discharges with an empirically calculated reserve. By keeping the SoC at an optimum level, it charges up faster with the cheaper morning electrons to arbitrage the peak hours.

For instance, I can find a reserve value (70%, 50%, or 20%) that will give me maximum annual feed-in credits vs an arbitrary setting. I've done some simulations and this can work, but requires very controlled discharging.

 

[zanary]

Lookie what showed up today. Looks like the iOS version of the Tesla App was updated this afternoon and a new Customize feature showed up today. I'm still on Powerwall OS 1.11.2.

I'm guessing that the mobile app has arrived in preparation for ToU without PV which should arrive mid February (that was the last I was told) for all of us with Powerwall without PV.

Woohoo!

 

[liuping]

ship before a Tesla Roaster gets to Mars' Orbit. Probably."

Lookie what showed up today. Looks like the iOS version of the Tesla App was updated this afternoon and a new Customize feature showed up today. I'm still on Powerwall OS 1.11.2.

I'm guessing that the mobile app has arrived in preparation for ToU without PV which should arrive mid February (that was the last I was told) for all of us with Powerwall without PV.

Woohoo!

I seems like they streamlined it a bit, but the option to set the reserve was there before, you just had to go to another page to set the backup reserve.

 

[zanary]

I seems like they streamlined it a bit, but the option to set the reserve was there before, you just had to go to another page to set the backup reserve.

There was no setting the reserve for just Powerwall (without PV) owners. This is the first we've seen it. All the capabilities excited for PV owners, but up to this point without PV, all you had were the other two options.

This is huge for us Powerwall no PV owners.

 

[liuping]

There was no setting the reserve for just Powerwall (without PV) owners. This is the first we've seen it. All the capabilities excited for PV owners, but up to this point without PV, all you had were the other two options.

This is huge for us Powerwall no PV owners.

Ah. Cool. Hopefully the TOU firmware update is out soon.

 

[zanary]

Ah. Cool. Hopefully the TOU firmware update is out soon.

I was told the week of February 12 last month. I'm hoping this is a sign that it's true!