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Cost savings vs. balanced

Sep 24, 2015
835
698
San Diego (Oceanside)
My PW's have been in self powered since installation. Now that the 90+ degree weather ended my self powered steak, I'd like to understand the difference between cost savings vs. balanced for my specific tariff.

During winter, I only have off peak and semi peak at basically the same price of $.22 kwh. During summer, off peak is roughly $.25 kwh, off peak and peak $.42 kwh. Off peak is 10p-6a weekdays and all weekend.

If I set peak in the PW to 6a - 10p weekdays, PW understands cheap is 10p-6a.

The 'learn more' states that PW will charge during off peak / shoulder. There's no sun during my off peak. Will choosing balanced or cost savings mean the PW won't charge?

The behavior I'd like when its hot is for the solar/pw to help during 6a-10p with cooling, charge PW in the AM/mid morning, then after 10p switch to grid to keep the PW from getting too low when the AC runs at night which would extend charge time the next day.

Thanks for any suggestions.
 

miimura

Well-Known Member
Aug 21, 2013
6,495
6,260
Los Altos, CA
In my experience, Cost Saving mode does not work well if you don't have solar generation during Off-Peak. Balanced has worked well for me in that situation, but the behavior is not as predictable as I would have liked during the Shoulder (Part-Peak) period.

It's not clear to me from your post when your shoulder is. I'm sure your're not being charged $0.42/kWh starting at 6am.
 

eml2

Member
Sep 28, 2017
272
214
Massachusetts
Balanced mode also works well for me and is predictable. Here is my experience with Balanced mode:
  1. Regardless of periods (peak/shoulder/off-peak), excess solar will go to charge PW. When PW is full, then export to grid
  2. During peak, PW will try very hard not to use grid. If solar is not enough to satisfy house load, PW will discharge to cover
  3. During shoulder, PW will not try as hard not to use grid. I notice it will draw some power from the grid for up to 30 seconds at a time
  4. When it first switch to off-peak, it will stop discharging PW and use the grid. Before the end of the off-peak, if PW still has a lot of stored energy above reserve, it will start to discharge before the end of off-peak. It seems to me that it is trying to get closer to the reserve at the end of off-peak.
 
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Sep 24, 2015
835
698
San Diego (Oceanside)
I'm sure your're not being charged $0.42/kWh starting at 6am.

I am.

I left it in balanced and this AM (7 when I looked) the house was running on what was left of the battery and the solar was all going to the grid. I'm guessing once the PW hit reserve, the solar would power the house and export and leave the battery at minimums. I had to switch it to Self Powered to get it to charge the battery. I'm guessing I'm going to have to fake a shoulder period. Maybe until noon?

Screen Shot 2020-08-19 at 4.20.16 PM.png



Screen Shot 2020-08-19 at 4.20.39 PM.png
 
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getakey

Active Member
Jan 28, 2020
1,416
451
95762
Balanced mode also works well for me and is predictable. Here is my experience with Balanced mode:
  1. Regardless of periods (peak/shoulder/off-peak), excess solar will go to charge PW. When PW is full, then export to grid
  2. During peak, PW will try very hard not to use grid. If solar is not enough to satisfy house load, PW will discharge to cover
  3. During shoulder, PW will not try as hard not to use grid. I notice it will draw some power from the grid for up to 30 seconds at a time
  4. When it first switch to off-peak, it will stop discharging PW and use the grid. Before the end of the off-peak, if PW still has a lot of stored energy above reserve, it will start to discharge before the end of off-peak. It seems to me that it is trying to get closer to the reserve at the end of off-peak.

In #4. if thats the way it works, you could be powering house with power stored at Shoulder Rates rather than powering house with Off Peak rates from Grid. That's not right
 

miimura

Well-Known Member
Aug 21, 2013
6,495
6,260
Los Altos, CA
I am.

I left it in balanced and this AM (7 when I looked) the house was running on what was left of the battery and the solar was all going to the grid. I'm guessing once the PW hit reserve, the solar would power the house and export and leave the battery at minimums. I had to switch it to Self Powered to get it to charge the battery. I'm guessing I'm going to have to fake a shoulder period. Maybe until noon?
Wow. Just Wow. Semi-Peak the same price as Peak. I knew SDGE was expensive, but that's nuts.

Two options.
1. Set the Partial Peak according to the schedule even though it's the same price as Peak. This is like your "fake shoulder" above.
2. Don't set any Peak at all. Off-Peak is according to the schedule and the rest is Shoulder. I've personally never tried this, but the idea is that it might act like Self-Powered during the middle of the day.

In the end, it really depends on the relative size of your solar compared to your Powerwall capacity compared to your consumption. However, having it set to Peak during the whole solar generating period is not going to work well.
 
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Reactions: NathanielHrnblwr
Sep 24, 2015
835
698
San Diego (Oceanside)
I set it to option #2 and will see how it goes. I had to use balanced as cost savings started discharging the PW during the day. It's going to warm up here over the next few days so hopefully this works.

I have the AC set to 77 at 10pm (vs 79 during the day) so both compressors will kick on then and run randomly through the night. At 5am, I have them set to 73 to attempt to cool the house as much as possible before rates jump at 6am when the AC goes back to 79.

EDIT: Nope, both balanced and cost savings seems to pull from the battery from shoulder while exporting all solar to grid.

Any other suggestions?
 
Last edited:
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