Powerwalls during PG&E PSPS 2020-10-25

[miimura]

Getting back to the Price Schedule settings, I'm curious how the Northern CA/PGE folks handle the partial peak period. I too, live in Northern CA, Oakland to be exact, and I entered the exact times for Peak (4 - 9) and Off-peak (12 - 3). Although you can't directly enter the time for partial peak, it appears that it still calculates it and shows it in the diagram. What I don't know is how it handles the partial peak time in terms of decisions about charging or sending back to the grid. Does it treat it like Peak, Off-peak, or some combination? I know some people just set Peak to include the partial peak time. How do others with PGE approach that?

If you have enough energy generated by your solar, it will eliminate the grid usage during Part-Peak and even export solar if available. When I had enough solar generation, my system would try to get to 100% before 3pm, the start of my Part-Peak period. Now that my generation is barely enough to cover my Peak usage, it allows the house to draw from the grid during that 3-4pm Part-Peak hour and just uses battery energy for the Peak period.

You can see in the chart below, it stopped charging at 3:15pm and ran down to the Reserve at about 8:55pm.

Earlier in the fall when there was more generation, it got to 100% before 3pm and then let the surplus solar export. It also mostly powered the house through the evening Part-Peak until midnight.

 

[RobbL]

@miimura, I see from your images that you have chosen to enter Peak exactly as it is defined by PGE, and having the partial peak fill in those undefined times. And you are right, the amount of solar generation is a moving target as we move into Fall and Winter. My question, though, is what decisions is the system making about those partial peak periods? Does it treat them like Off-peak? How does it weigh the partial peak times as it makes decisions as to energy use and allocation?

 

[getakey]

I eliminated partial peak. App does strange things

 

[RobbL]

@getakey, so have you set it up again to now include partial peak? Did you enter peak exactly in the hours it covers?

 

[arnolddeleon]

If you have enough energy generated by your solar, it will eliminate the grid usage during Part-Peak and even export solar if available. When I had enough solar generation, my system would try to get to 100% before 3pm, the start of my Part-Peak period. Now that my generation is barely enough to cover my Peak usage, it allows the house to draw from the grid during that 3-4pm Part-Peak hour and just uses battery energy for the Peak period.

What I've observed is that my system in Cost Savings mode will happily charge and discharge during part peak depending on what I think its prediction is. For example, if I've been running air conditioning so my peak load is high, it will charge during part peak because it expects to dump it during peak. On the other hand sometimes it correctly predicts that peak load will be low so it makes sense to discharge energy that was gather from off peak during part peak as well. I've also seen it charge and discharge in part peak on the same day I suspect this occurs when the batteries are not full yet when it enters part peak but predicts it will need energy from part peak to cover the peak but then the situation changes and it decides that it can make more money by discharging during par peak as well (assuming it had some off peak energy stored).

Today I noticed an interesting case, it didn't charge to 100%. When it reach part peak it stopped charging. I suspect this is because it predicted that it had enough energy stored to cover the peak load (which turned out to be correct) and I think it is waiting for the weekend to fully charge the batteries with off peak power.

 

[MorrisonHiker]

Getting back to the Price Schedule settings, I'm curious how the Northern CA/PGE folks handle the partial peak period. I too, live in Northern CA, Oakland to be exact, and I entered the exact times for Peak (4 - 9) and Off-peak (12 - 3). Although you can't directly enter the time for partial peak, it appears that it still calculates it and shows it in the diagram. What I don't know is how it handles the partial peak time in terms of decisions about charging or sending back to the grid. Does it treat it like Peak, Off-peak, or some combination? I know some people just set Peak to include the partial peak time. How do others with PGE approach that?

This page describes it a little more: Powerwall Time-Based Control | Tesla Support

They used to have another page with a confusing table but I can't find it anymore.

We use peak, part-peak and off-peak schedules. Since there is no "scheduled self-powered" mode, we use the balanced time-based mode and schedule the peak and part-peak periods to be longer than they really are. This allows us to run off the Powerwalls for 22 hours a day.

 

[getakey]

What I've observed is that my system in Cost Savings mode will happily charge and discharge during part peak depending on what I think its prediction is. For example, if I've been running air conditioning so my peak load is high, it will charge during part peak because it expects to dump it during peak. On the other hand sometimes it correctly predicts that peak load will be low so it makes sense to discharge energy that was gather from off peak during part peak as well. I've also seen it charge and discharge in part peak on the same day I suspect this occurs when the batteries are not full yet when it enters part peak but predicts it will need energy from part peak to cover the peak but then the situation changes and it decides that it can make more money by discharging during par peak as well (assuming it had some off peak energy stored).

Today I noticed an interesting case, it didn't charge to 100%. When it reach part peak it stopped charging. I suspect this is because it predicted that it had enough energy stored to cover the peak load (which turned out to be correct) and I think it is waiting for the weekend to fully charge the batteries with off peak power.

Thats exactly why I eliminated partial peak. It will stop charging on PArt Peak on Fridays in anticipation of the long Off Peak on the weekend. My problem with that is what happens if Saturday is suddenly cloudy and then you have an unexpected outage. The $ savings is peanuts for those short periods of time

 

[getakey]

@getakey, so have you set it up again to now include partial peak? Did you enter peak exactly in the hours it covers?

I have Peak exactly equaal to PG&E Peak, but all other time I put as Off Peak. This came as a suggestion from someone on this forum. Wish I could remember to give them credit

 

[power.saver]

I have Peak exactly equaal to PG&E Peak, but all other time I put as Off Peak. This came as a suggestion from someone on this forum. Wish I could remember to give them credit

It may have been me. I've been doing that for over a year now. The Part Peak algorithm just doesn't seem to work right.

 

[getakey]

It may have been me. I've been doing that for over a year now. The Part Peak algorithm just doesn't seem to work right.

I totally agree with you and thanks for the tip

 

[miimura]

@miimura, I see from your images that you have chosen to enter Peak exactly as it is defined by PGE, and having the partial peak fill in those undefined times. And you are right, the amount of solar generation is a moving target as we move into Fall and Winter. My question, though, is what decisions is the system making about those partial peak periods? Does it treat them like Off-peak? How does it weigh the partial peak times as it makes decisions as to energy use and allocation?

The system is just guessing based on available inputs. It would be much better if they would allow us to put the actual prices for each time period. If the feed-in (export) and consumption (import) prices are different, those should be input as well. With that data, it could do a better job of doing the right thing. As it is, it's really only optimal if you have true net metering. Luckily, I'm in NorCal near the Tesla HQ, so their assumptions, and resulting system behavior, works well for me.

The Part-Peak behavior is different than the Off-Peak and Peak behavior. When I have enough generation, it will usually fill to 100% during Off-Peak then export Surplus Solar during the afternoon. The Powerwall is actually in Standby in that case. That is my second chart above. If there is not enough solar during Part-Peak, it will let the power come from the grid and usually not charge or discharge the batteries during that period. This is like the first chart above. It was charging from solar at the beginning of Part-Peak but it stopped after about 15 minutes even though it was not full.

As it is, I am happy with the way it works in Balanced Mode. The only thing I do is raise the Reserve as the daily generation falls. I leave enough headroom above the Reserve for my daily solar generation. If you have a larger solar system, you would not need to do that.