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Tesla App Utility plan configuration: Multiple Peaks, Buy/Sell Behavior, etc

I agree with Redhill.

Although, while 0.01 for buy may be close to realistic for what the OP indicated the utility is charging (since I think the OP said they have zero charge for offpeak), like Redhill mentioned, I think to force the PW behavior the OP wants they'd want to fill in a higher number for Buy, say like 0.10 or higher, and for the sell side the OP should set a very much lower number, so could leave it at 0.01... those values should tell the PW that it doesn't make sense to sell back to the grid since the sell is so much lower than the buy. The closer those buy/sell values are, the less predictable it will be what the system does in terms of buying/selling power.

My experience has been that if the system sees a similar buy and sell, and if the system predicts any extra PV capacity (whether accurate or not), then most likely it will think it makes sense to offset usage by selling back to the grid if the costs are even close to similar (for buy and sell). I've never used 0.01 for buy and sell, but when I've set BOTH buy and sell values to be equal at around 4-5 cents, it has always tried to sell back to the grid for even the off-peak windows. Where as if buy is much higher than sell, then the system sees no benefit to selling power back to grid then it will focus on powering the house and/or raising the PW SOC.

So with BOTH buy and sell values set to 0.01 it's not surprising to me that the system was selling back to the grid based on my experience, even though selling for a single penny does seem ridiculous for sure relative to the OPs peak costs.
Thanks for the feedback. I may have had the same buy and sell values all along (peak and off-peak were more realistic at the start of my tests). I'll try using the values you suggest and report back. That said, things like draining the PW when the grid cost is $0.01, or nor sending solar to the grid when it sells for $1.50 doesn't make a lot of sense. Those look like software logic issues.
 
I'm still not seeing the result I'd like. This is what I'd like to see:
Off-peak: House is 100% powered by grid. Powerwall charges from solar then excess solar (if any) goes to grid
Peak: Powerwall powers house. All solar goes to grid
After changing the prices as recommended, I'm still seeing some Powerwall usage during off-peak and solar powering the house during peak

Until the latest software updates I had this working beautifully.

6kW solar, 1 Powerwall (Oct 2020). I'm on PG&E in California.
 

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miimura

Well-Known Member
Aug 21, 2013
7,187
7,146
Los Altos, CA
I'm still not seeing the result I'd like. This is what I'd like to see:
Off-peak: House is 100% powered by grid. Powerwall charges from solar then excess solar (if any) goes to grid
Peak: Powerwall powers house. All solar goes to grid
After changing the prices as recommended, I'm still seeing some Powerwall usage during off-peak and solar powering the house during peak

Until the latest software updates I had this working beautifully.

6kW solar, 1 Powerwall (Oct 2020). I'm on PG&E in California.
Because your solar is relatively large compared to your battery and usage, the battery SOC remains pretty high. If you don't want it to discharge during Off-Peak, try increasing the Reserve.
 
I'm still not seeing the result I'd like. This is what I'd like to see:
Off-peak: House is 100% powered by grid. Powerwall charges from solar then excess solar (if any) goes to grid
Peak: Powerwall powers house. All solar goes to grid
After changing the prices as recommended, I'm still seeing some Powerwall usage during off-peak and solar powering the house during peak

Until the latest software updates I had this working beautifully.

6kW solar, 1 Powerwall (Oct 2020). I'm on PG&E in California.
You didn't use the numbers that I recommended:
  • Off Peak - Buy $0.12 and Sell $0.10 (20%) versus your Buy $0.20 and Sell $0.16 (25%)
  • Peak - Buy $0.36 and Sell $0.30 (20%) versus your Buy $0.60 and Sell $0.58 (3.4%)
The 25% difference between the Buy/Sell during Off-Peak plus the system expecting that it can get your single Powerwall to 100% before Peak is likely why it is discharging. You want 100% solar to got to the Powerwall first before going to the Home/Grid, so I would recommend that you change your Off-Peak Buy/Sell to $0.20/$0.20 and leave your Peak as-is. The equal amounts during Off-Peak should have the system charge the Powerwalls at 100% as there is economic disadvantage of drawing from the grid.

Note: My earlier recommendation of 20% differential I think is too high to prevent unwanted discharges during Off-Peak my own settings are
  • Off Peak - Buy $0.07 and Sell $0.06 (16.7%)
  • Peak - Buy $0.10 and Sell $0.09 (11.1%)
This gets me what I want, with Powerwall discharge during Peak and Solar going to House first then Powerwall then Grid when recharging during Off-Peak. I do get a couple of blips of random discharge/charge during Off-Peak, but it is less than 0.5 kWh total during any single day.

Tesla Developer Lurkers - Again, please just give us the option to explicitly set the charge/discharge priorities by TOU period. We should not have to reverse engineer how your algorithm behaves in response to Buy/Sell levels.
 
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You didn't use the numbers that I recommended:
  • Off Peak - Buy $0.12 and Sell $0.10 (20%) versus your Buy $0.20 and Sell $0.16 (25%)
  • Peak - Buy $0.36 and Sell $0.30 (20%) versus your Buy $0.60 and Sell $0.58 (3.4%)
The 25% difference between the Buy/Sell during Off-Peak plus the system expecting that it can get your single Powerwall to 100% before Peak is likely why it is discharging. You want 100% solar to got to the Powerwall first before going to the Home/Grid, so I would recommend that you change your Off-Peak Buy/Sell to $0.20/$0.20 and leave your Peak as-is. The equal amounts during Off-Peak should have the system charge the Powerwalls at 100% as there is economic disadvantage of drawing from the grid.

Note: My earlier recommendation of 20% differential I think is too high to prevent unwanted discharges during Off-Peak my own settings are
  • Off Peak - Buy $0.07 and Sell $0.06 (16.7%)
  • Peak - Buy $0.10 and Sell $0.09 (11.1%)
This gets me what I want, with Powerwall discharge during Peak and Solar going to House first then Powerwall then Grid when recharging during Off-Peak. I do get a couple of blips of random discharge/charge during Off-Peak, but it is less than 0.5 kWh total during any single day.

Tesla Developer Lurkers - Again, please just give us the option to explicitly set the charge/discharge priorities by TOU period. We should not have to reverse engineer how your algorithm behaves in response to Buy/Sell levels.
My bad! I had modified the numbers some more this morning, and my attempt to revert to what was used yesterday failed. Peak was $0.60 / $0.48.

I now have off-peak set to $0.20 / $0.20 and peak at $0.60 / $0.48. I'll collect a day's worth of graphs on Thursday. I'm not hopeful though given I started with off-peak set to $0.01 / $0.01.

With only 1 Powerwall, bad weather can leave it at less than 100% when peak rates start. Add a heavy usage day like Thanksgiving I can easily need to draw power from the grid at peak rates. I agree with your appeal to Tesla Developers - it shouldn't be this difficult!
 

slcasner

Active Member
Supporting Member
Feb 20, 2011
1,529
1,066
Sunnyvale, CA
I'm still not seeing the result I'd like. This is what I'd like to see:
Off-peak: House is 100% powered by grid. Powerwall charges from solar then excess solar (if any) goes to grid
Peak: Powerwall powers house. All solar goes to grid
The system can't work exactly as stated because the grid, home, solar and battery are all connected together. If the Powerwall and/or solar sources push harder on that connection point so the voltage is greater than what the grid is trying to deliver, then power will flow back to the grid. If they are pushing less so the voltage is lower, then power will be drawn from the grid.

In off-peak you can't have some electrons going from solar to the grid while other electrons come from the grid to power house loads. The two cancel out. A more accurate description would be that in off-peak any excess solar (if greater than the Powerwall maximum charge rate or after the Powerwall fills) powers house loads and then any further excess goes to the grid. If the house load is greater than the excess solar, the balance is drawn from the grid.

Similarly for Peak, there aren't two separate pathways for power to flow. Stating that the Powerwall powers the house means that you are asking the Powerwall to discharge at the same rate as the house load. (Discharging at a higher rate than the house load would not be allowed because that would flow to the grid.) If solar is also pushing power at the common connection point, that power would flow to the grid. But if the house load is greater than what the Powerwall can supply, part or all of the solar will go to the house load. Any excess will go to the grid.
 
The system can't work exactly as stated because the grid, home, solar and battery are all connected together. If the Powerwall and/or solar sources push harder on that connection point so the voltage is greater than what the grid is trying to deliver, then power will flow back to the grid. If they are pushing less so the voltage is lower, then power will be drawn from the grid.

In off-peak you can't have some electrons going from solar to the grid while other electrons come from the grid to power house loads. The two cancel out. A more accurate description would be that in off-peak any excess solar (if greater than the Powerwall maximum charge rate or after the Powerwall fills) powers house loads and then any further excess goes to the grid. If the house load is greater than the excess solar, the balance is drawn from the grid.

Similarly for Peak, there aren't two separate pathways for power to flow. Stating that the Powerwall powers the house means that you are asking the Powerwall to discharge at the same rate as the house load. (Discharging at a higher rate than the house load would not be allowed because that would flow to the grid.) If solar is also pushing power at the common connection point, that power would flow to the grid. But if the house load is greater than what the Powerwall can supply, part or all of the solar will go to the house load. Any excess will go to the grid.
Leaving the Powerwall out of it, then you are correct that the grid, home and solar are connected. Powerwall has hall-effect sensors that measure the current used by the house and produced by solar. Since it also knows the voltage it can calculate the power - which is what is displayed in the app.

Powerwall has both an inverter and a charger. These both appear to be smart and can charge/discharge the batteries at whatever rate Powerwall decides is correct. So by measuring house power consumption it is able to have its inverter produce power at the same rate. So it is possible to have a situation where the Powerwall is providing all the house's power needs, and at the same time all the solar production is going to the grid.

I believe there are relays in the Telsa Gateway that also help with redirecting power between the various sources.

Until the recent software updates this was working, so I know it can work as I want it to.
 
I believe there are relays in the Telsa Gateway that also help with redirecting power between the various sources.
The only relay in the GW is the main contactor that isolates the home from the grid in a grid out scenario.

Otherwise as @slcasner said everything is directly tied together. Think of it as a series of pipes directly teed together. You can only change how fluid flows between the various sources and sinks by changing their relative pressure. You can't have the fluid flowing both directions in the same pipe.


I think the only error in your scenario is the off peak behavior. You can't have the house 100% powered by the grid and send solar power back to the grid. Power can only flow both directions at a time.
 

slcasner

Active Member
Supporting Member
Feb 20, 2011
1,529
1,066
Sunnyvale, CA
Until the recent software updates this was working, so I know it can work as I want it to.
By that do you mean you saw the power flow graphic in the v3 app showing power flowing from solar and curving to the grid while power flowing from the Powerwall curved to the home? That graphic was an illusion because there aren't separate paths. There really should just have been a dot in the center with all four lines connected to it. Solar and Powerwall would both be pushing power towards that dot while power flowed out to the grid and home. By looking at the power numbers you could tell whether the flow to the grid was the same as what was produced by solar (and in that case the amount discharged by the Powerwall and the amount consumed by the home would also have to be equal). Note that the graphic in the v4 app has the image of the main service panel in the center with all four lines connected to it.
 
I still see the Powerwall discharging during the 12am - 3pm off-peak period. I also see solar powering the house after 3pm, instead of sending production to the grid. To recap, this is what I want to achieve:
Off-peak: Powerwall does not discharge. Solar charges Powerwall first, after which solar can go to the home or grid
Peak: Powerwall powers house. All solar goes to grid

This used to work until the recent software updates.
 

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I still see the Powerwall discharging during the 12am - 3pm off-peak period. I also see solar powering the house after 3pm, instead of sending production to the grid. To recap, this is what I want to achieve:
Off-peak: Powerwall does not discharge. Solar charges Powerwall first, after which solar can go to the home or grid
Peak: Powerwall powers house. All solar goes to grid

This used to work until the recent software updates.
I've been seeing the same behavior as you and have been trying without success to achieve the same behavior you're seeking, including trying some of the tweaks @Redhill_qik suggested.

additionally, there's a message in the app saying Powerwall will not cycle this season because the the differences in peak and off-peak rates are insufficiently small...yet the Powerwalls ARE indeed cycling...
 
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Off-peak: House is 100% powered by grid. Powerwall charges from solar then excess solar (if any) goes to grid

Based on what I've been seeing in testing with my own system, you're going to need to zero our your Off-peak sell value, it will need to be 0.00 if you want to see no PW usage during off-peak. Also, in my case I've set that period to "Super Off Peak", with a sell value of 0.00 and I'm finally getting the behavior I expect. To be sure, I eventually need to set it back to "off-peak" with a sell value of 0.00 - but right now Super Off-Peak is working this way with a zero sell value. It looks like maybe you still have 0.20 for your off peak sell value in the snapshots, and you might try changing that period to Super Off Peak.

Similar to what you saw, when I had my Off-Peak set to sell with even just a 0.01 sell value, if the SOC was high it would at times power the house from the PW. It does seem to me setting a much lower sell than buy should be enough to tell the system not to discharge the power wall during off-peak, but right now in my testing it has done so unless I zero out the off-peak sell value.

I also see solar powering the house after 3pm, instead of sending production to the grid.
From the snapshots, it seems like you have maybe a high reserve set on those days where you took the snapshots you show, like 62%, and your POW charge chart shows your SOC is not much above this during most of the day (athough clearly that's also because it was discharging when you didn't want it too - so note above applies). Because of this I think it's going to try to power the house from solar first, and if possible rebuild SOC buffer that it thinks you need to cover your entire peak window plus any peak-period usage spikes and such over and above that reserve level. Just my best guess, but based on information shown in your snapshots this one isn't too surprising to me. So I'm guessing you were caught in a bit of a cycle with setting the reserve high to get it to stop discharging during offpeak, while at the same time these changes impacting the behavior of the system during peak.

The change of sell to 0.00, and setting it to super off-peak, and lowering the reserve and leaving it there to all settle in, all taken together may help solve this ultimately. Just my best guesses, but that seems to be working for me.
 
Last edited:

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
14,240
17,978
Riverside Co. CA
Thanks for the info!

Sure, np. FWIW, if you use self powered mode with a reserve, you are also lessening your impact on the grid (meeting the "pull less from the grid" objective you mentioned). The only "issue" if you can call it that, is that powerwalls are only (roughly) 90% efficient, so you are losing some of the solar power by running it through the powerwalls, provided you have net metering and are allowed to export to the grid.

Your location says honolulu, and I thought I remembered Hawaii being pretty restrictive on whether you could feed back to the grid at all, so if thats the case for you (no grid export at all), then you likely want to get as much use out of your solar as possible, so that also matches self powered mode with a reserve that makes sense to you (enough to get you through the night till morning sunrise, etc).
 
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