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Powerwall - Settings Q

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H

hslee

Member
Jun 24, 2020
18
0
Boston, MA
#1
I recently got my PTO on 2/12 this year. Despite the gloomy weather and snow on my panels (which is finally melting - we have odd peaks/valleys on the roof), I am quite happy with the setup.

I live in MA and have municipal utility that has crappy net metering so it isn't typically worth sending power back to the grid. The rate that is credited is only the wholesale rate. AND recently switched to TOU (12pm to 7pm is peak, the rest is a lower rate including the weekend).

My question: Is it possible to send back all my solar generation back to the grid during peak and just use the battery during the peak time (I usually have enough battery power to last me the peak hours).

I need to confirm but I believe I would be credited the higher rate during peak which would make it worth it - definitely not during off-peak. Let's assume that this is the case.

I reviewed what I could by searching and googling and I didn't see if it is possible. I don't think it is possible - unless I am missing something. So I am checking here. Thanks!
 
#3
Hmmm, maybe I mis-understood OP's post but I think he wants to bank the solar energy collected from 8am to noon in his Powerwalls. Then once he enters peak time, he has his Powerwalls discharge some (but not all) to the grid in addition to whatever solar he's producing in excess of what is consumed by his house.

It seems like he thinks the residual energy left in the battery after dusk can carry him to 7pm where his TOU rates drop to the cheaper tier.
 
#4
holeydonut said:
Hmmm, maybe I mis-understood OP's post but I think he wants to bank the solar energy collected from 8am to noon in his Powerwalls. Then once he enters peak time, he has his Powerwalls discharge some (but not all) to the grid in addition to whatever solar he's producing in excess of what is consumed by his house.

It seems like he thinks the residual energy left in the battery after dusk can carry him to 7pm where his TOU rates drop to the cheaper tier.
Click to expand...

Yes. Usually most mornings we have enough solar banked in the PW to cover the peak hours of 12-7pm.

Ideally the PW is 100% used by the house and all solar is pushed back to the grid.

Is that possible?
 
#5
hslee said:
Yes. Usually most mornings we have enough solar banked in the PW to cover the peak hours of 12-7pm.

Ideally the PW is 100% used by the house and all solar is pushed back to the grid.

Is that possible?
Click to expand...

If I understand what you are asking correctly. Either of the Advanced Time Base Settings (Balanced and Cost Savings) will do what you want or come close.

First you have set peak hours correctly in the app. The PW will charge from solar in the morning using "off peak" hours. If you are set for Cost Saving the PW will likely consume all the solar it can absorb. If you are set for balanced the PW will probably consume the surplus solar (what is left after house loads) to charge itself. The behavior may differ based on the forecast that Tesla is making and what it has learned of your patterns. Once the batteries are full then the PW will go on standby. Once peak rates kick in the PW will start discharging to offset what your house is consuming. This will result in "all" your solar going to the grid. Depending the size of your battery, battery reserve, solar and history of consumption, the Tesla PW may choose to start right at the beginning of peak or somewhere later. It will generally try use up all the stored energy just before the next set of peak hours. I'm not remembering at the moment what differences might occur between Balanced and Cost Saving during this phase.
 
#6
holeydonut said:
Hmmm, maybe I mis-understood OP's post but I think he wants to bank the solar energy collected from 8am to noon in his Powerwalls. Then once he enters peak time, he has his Powerwalls discharge some (but not all) to the grid in addition to whatever solar he's producing in excess of what is consumed by his house.

It seems like he thinks the residual energy left in the battery after dusk can carry him to 7pm where his TOU rates drop to the cheaper tier.
Click to expand...

Maybe I am reading it differently but I didnt read anything about pushing powerwall energy to the grid. I read about pushing solar energy to the grid while running on powerwalls.

hslee said:
I
My question: Is it possible to send back all my solar generation back to the grid during peak and just use the battery during the peak time (I usually have enough battery power to last me the peak hours).

I need to confirm but I believe I would be credited the higher rate during peak which would make it worth it - definitely not during off-peak. Let's assume that this is the case.

I reviewed what I could by searching and googling and I didn't see if it is possible. I don't think it is possible - unless I am missing something. So I am checking here. Thanks!
Click to expand...

Advanced setting should send solar generation to the grid during whatever the defined peak time is, while the home runs on the powerwall energy. Maybe I am reading the question incorrectly though.
 
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#7
What utility provider do you have? What size is your system (ac and dc)?

I ask since I’m in Mass and wasn’t aware of much in the way of TOU plans, well any that were even close to worth while.
 
#8
TORQU3 said:
What utility provider do you have? What size is your system (ac and dc)?

I ask since I’m in Mass and wasn’t aware of much in the way of TOU plans, well any that were even close to worth while.
Click to expand...

Solar: 8.84k, 10kW SolarEdge inverter and PW 27kW.

RMLD is the utility that offers TOU. We are forced to stick to a rate plan for a year - I will share the data after a few months on TOU + Solar + PW. So I am hoping with a certain pattern of usage with the Powerwalls I can maximize savings. So far I have been able to not pull from the grid during peak hours of 12-7pm for most days. On the days that I did need to pull from the grid it was cloudy/storms and after the last large snow storm - the panels had snow on them. I need to be better about ensuring that the snow has a chance to slide off the roof (hopefully no more snow storms this year!).

Today is a nice sunny day. My current settings is Advanced: Time-Based: Cost Savings. I set the peak at 12-7pm and off-peak for the rest of the hours (weekdays). Weekends are all off-peak. Currently (9am EST), I have perhaps 3 panels with still some snow and I am pulling 6kW. However, I would have thought with my current settings all of the solar would go to the battery until it hits 100% - usual pattern, and the house would use 100% grid. At the moment, the house and battery are using solar (no grid). Battery is at 80% at the moment.

Seemingly based on history, the pattern is different.
 
Last edited:
#9
hslee said:
Solar: 8.84k and PW 27kW.

RMLD is the utility that offers TOU. We are forced to stick to a rate plan for a year - I will share the data after a few months on TOU + Solar + PW. So I am hoping with a certain pattern of usage with the Powerwalls I can maximize savings. So far I have been able to not pull from the grid during peak hours of 12-7pm for most days. On the days that I did need to pull from the grid it was cloudy/storms and after the last large snow storm - the panels had snow on them. I need to be better about ensuring that the snow has a chance to slide off the roof (hopefully no more snow storms this year!).

Today is a nice sunny day. My current settings is Advanced: Time-Based: Cost Savings. I set the peak at 12-7pm and off-peak for the rest of the hours (weekdays). Weekends are all off-peak. Currently (9am EST), I have perhaps 3 panels with still some snow and I am pulling 6kW. However, I would have thought with my current settings all of the solar would go to the battery until it hits 100% - usual pattern, and the house would use 100% grid. At the moment, the house and battery are using solar (no grid). Battery is at 80% at the moment.

Seemingly based on history, the pattern is different.
Click to expand...

I dont use that mode (advanced) but its my understanding that there are some algorithms at play, where its trying to calculate how much it needs to fill the batteries to last through peak, etc. I have read about people saying that it sometimes does things they dont understand, and also read about that it sometimes takes a few days for the system to sort of figure out what its supposed to do.
 
#10
I know others have requested or suggested it but there should be an option for perhaps finer grain control. Largely since there is so much variation from installation to installation potentially. Or set better goals for the system instead of the ability to fine tune it. I would love a goal to be to maximize savings that understands the net metering plans that we may or may not have.

I can get Tesla wanting to have a "black box" to optimize for the general population and they may need to due to the warranty that they offer. I am new install so I am hopeful that the system will generally do the right thing :)
 
#11
hslee said:
Solar: 8.84k, 10kW SolarEdge inverter and PW 27kW.

RMLD is the utility that offers TOU. We are forced to stick to a rate plan for a year - I will share the data after a few months on TOU + Solar + PW. So I am hoping with a certain pattern of usage with the Powerwalls I can maximize savings. So far I have been able to not pull from the grid during peak hours of 12-7pm for most days. On the days that I did need to pull from the grid it was cloudy/storms and after the last large snow storm - the panels had snow on them. I need to be better about ensuring that the snow has a chance to slide off the roof (hopefully no more snow storms this year!).

Today is a nice sunny day. My current settings is Advanced: Time-Based: Cost Savings. I set the peak at 12-7pm and off-peak for the rest of the hours (weekdays). Weekends are all off-peak. Currently (9am EST), I have perhaps 3 panels with still some snow and I am pulling 6kW. However, I would have thought with my current settings all of the solar would go to the battery until it hits 100% - usual pattern, and the house would use 100% grid. At the moment, the house and battery are using solar (no grid). Battery is at 80% at the moment.

Seemingly based on history, the pattern is different.
Click to expand...


Ahh you are on a municipal power provider. Did they have different net metering rules? What kind of TOU pricing do you have?
 
#12
TORQU3 said:
Ahh you are on a municipal power provider. Did they have different net metering rules? What kind of TOU pricing do you have?
Click to expand...

I assume all the municipal can have different plans in MA. RMLD isn't as straightforward as I would like. There are several different charges however the TOU primary affects the fuel charge (there are other slight changes):
  • Standard Plan - fuel charge is ~.04 per kWH. With the other charges, it is about .015 per kWH
  • TOU: off-peak fuel charge is ~.02 per kWH and peak is ~.08 per kWH (not sure the the total charges are yet).
BTW, I am in my peak period and the battery is full and not being used unfortunately. Cost-Saving Mode during 12pm to 7pm. Solar is powering the house and sending the excess to the grid - which is not is optimal for my use case.
 
#15
hslee said:
I assume all the municipal can have different plans in MA. RMLD isn't as straightforward as I would like. There are several different charges however the TOU primary affects the fuel charge (there are other slight changes):
  • Standard Plan - fuel charge is ~.04 per kWH. With the other charges, it is about .015 per kWH
  • TOU: off-peak fuel charge is ~.02 per kWH and peak is ~.08 per kWH (not sure the the total charges are yet).
BTW, I am in my peak period and the battery is full and not being used unfortunately. Cost-Saving Mode during 12pm to 7pm. Solar is powering the house and sending the excess to the grid - which is not is optimal for my use case.
Click to expand...

How long ago did you make the change to advanced? If it was "yesterday" I believe it takes a few days for those advanced algorithms to kick in.
 
#17
hslee said:
Actually it has been in this mode since 2/12 - anyways I will keep it and see how it goes.
Click to expand...

I use self powered myself so am not too familiar with this mode other than what tesla says on it and what I read from others here. I do remember reading others say there is strange behavior with setting "shoulder" periods instead of simply peak and off peak, but from reading what you posted, you only used peak and off peak, so thats not it.

Wish I could help you more on this.
 
#19
Contact Tesla.... I got my PTO in early Feb but my PW wasn't discharging consistently during peak hours. I called Tesla twice and the CS I talked to on my 2nd call understood the problem and said he would ask the other team to look at it.... After a couple days my PW is discharging during peak hours while sending all solar to the grid like it is supposed to.
 
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#20
I am going give it another 2 weeks and see what happens. Not sure if the snow covered panels + cloudy weather has thrown the algorithm off. I am watching Power Flow UI and it is “everywhere” in terms of behavior - not consistent at all in terms of solar flows to the grid/house and the battery occasionally powering the house.
 
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