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Are these operating modes possible?

RKCRLR

Member
Apr 13, 2020
434
168
Garden Valley, CA
During off-peak I'd like the house to run off solar with the excess recharging the Powerwalls, and then excess solar to the grid once the Powerwalls are charged; and NEVER discharge the Powerwalls during this period.

During peak I'd like the house to run off solar with the excess going to the grid with the house running off the Powerwalls (until the reserve is hit) when there isn't sufficient solar; and the Powerwalls are NEVER recharged during this period.

Is this possible?
 

getakey

Active Member
Jan 28, 2020
1,321
429
95762
In cost saving mode, PWs will never charge during Peak. They will run the house until reserve is hit. During Off Peak, Solar will charge PWs until 100% and then power house and/or send to grid depending on house draw
 

RKCRLR

Member
Apr 13, 2020
434
168
Garden Valley, CA
In cost saving mode, PWs will never charge during Peak. They will run the house until reserve is hit. During Off Peak, Solar will charge PWs until 100% and then power house and/or send to grid depending on house draw
I'm using cost saving mode now. However, during off-peak priority is given to recharging the Powerwalls and the house runs off the grid until the Powerwalls are recharged. During peak all solar is diverted to the grid and the house runs completely off the Powerwalls with no solar going to the house.

This type of operation increases NBCs and, during peak, increases the cycles on the Powerwalls.
 

getakey

Active Member
Jan 28, 2020
1,321
429
95762
I'm using cost saving mode now. However, during off-peak priority is given to recharging the Powerwalls and the house runs off the grid until the Powerwalls are recharged. During peak all solar is diverted to the grid and the house runs completely off the Powerwalls with no solar going to the house.

This type of operation increases NBCs and, during peak, increases the cycles on the Powerwalls.
That is all true and will save you money. What is your priority?
 

RKCRLR

Member
Apr 13, 2020
434
168
Garden Valley, CA
My annual solar generation is about equal to my annual production. I.e., if I were still under NEM 1 and on a basic non-tiered rate plan I would have a $0 true-up (and no NBCs).

Under NEM 2 and EV2A, the Powerwalls basically are used to offset the TOU rates (the main objective is to have the Poweralls as backup during an outage).

My goal is to have a $0 true-up while minimizing NBCs and cycling of the Powerwalls, and still keep a reasonable reserve for power outages.
 

Redhill_qik

Member
Aug 16, 2020
305
216
South SF Bay, California
During off-peak I'd like the house to run off solar with the excess recharging the Powerwalls, and then excess solar to the grid once the Powerwalls are charged; and NEVER discharge the Powerwalls during this period.

During peak I'd like the house to run off solar with the excess going to the grid with the house running off the Powerwalls (until the reserve is hit) when there isn't sufficient solar; and the Powerwalls are NEVER recharged during this period.

Is this possible?
It is not possible with the current configurations supported by the app and this is exactly how I want to operate it as well.

I switch to Cost Savings in the afternoon before Peak and then to Balanced when I wake up to feed the dog her meds & breakfast at 6:30am before solar starts generating. Highly annoying, but it gets the behavior.
 
Last edited:

Redhill_qik

Member
Aug 16, 2020
305
216
South SF Bay, California
That is all true and will save you money. What is your priority?
How does importing from the grid save you money while sending 100% of solar to recharging the PWs?

First, it is inefficient to be pulling from the grid from a remote source when the rooftop solar can be powering the house and recharging due to line losses.

Second, in CA you are incurring at least NBCs for the imported kWh during this period. The MDC of $0.32854/day gets you about 15 kWh of NBCs at no additional charge, but if/when NEM 3.0 drops the 100% credit for exports then the cost to import during the recharge will go up significantly making this mode even more desirable.
 

wjgjr

Active Member
May 11, 2020
1,254
998
Silver Spring, MD
It is not possible with the current configurations supported by the app and this is exactly how I want to operate it as well.
I agree it appears to not be possible with the Tesla app. It seems like what is needed is to run in "cost savings" mode during peak and "self powered" other times. Since the API does include the ability to change the operating mode, an option might be to look at solutions that have been implemented to use the API to schedule mode changes. This might get you what you need unless and until Tesla adds more options to their own app.

It seems like Tesla should at least add an option to indicate you have NBCs. When those exist, the software could potentially be configured to still get the PWs to 100% in time for peak, but only pull home load from the grid where it appears (based on usage and weather) that solar alone won't be able to do the job. Right now, it seems like Tesla assumes all grid imports/exports are full net metering. So, while it provides for TOU rates, it does not consider the potential asymmetry between import and export amounts.
 
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RKCRLR

Member
Apr 13, 2020
434
168
Garden Valley, CA
It seems like Tesla should at least add an option to indicate you have NBCs. When those exist, the software could potentially be configured to still get the PWs to 100% in time for peak, but only pull home load from the grid where it appears (based on usage and weather) that solar alone won't be able to do the job. Right now, it seems like Tesla assumes all grid imports/exports are full net metering. So, while it provides for TOU rates, it does not consider the potential asymmetry between import and export amounts.
Not hitting 100% charge would be my main concern about prioritizing the home during of-peak hours.

If Tesla had a Utopia plan for me, it would be to have a $0 annual true-up target that hones in on the goal while minimizing NBCs and cycles. It would take actual rate schedules and NBC costs into account.

But I suspect Tesla is unable or unwilling to do something like this.
 

arnolddeleon

Supporting Member
Jul 21, 2012
841
909
SF Bay Area
During off-peak I'd like the house to run off solar with the excess recharging the Powerwalls, and then excess solar to the grid once the Powerwalls are charged; and NEVER discharge the Powerwalls during this period.

During peak I'd like the house to run off solar with the excess going to the grid with the house running off the Powerwalls (until the reserve is hit) when there isn't sufficient solar; and the Powerwalls are NEVER recharged during this period.

Is this possible?

Have you tried "balanced"? It tries to be self-powered in whenever practical. When it is charging the Powerwalls it will only take the excess so the you are not pulling or pushing to the grid (unless your off peak window is so small that it thinks it needs all of it to charge the PW for the peak period). You can use the "shoulder" (aka part peak) setting to bias when you want to it to use the batteries during real off peak hours if you want to fine tune it.

I've been running in balanced for a little while now it and it seems to do the job reasonably well.
 
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RKCRLR

Member
Apr 13, 2020
434
168
Garden Valley, CA
I agree it appears to not be possible with the Tesla app. It seems like what is needed is to run in "cost savings" mode during peak and "self powered" other times.
Is there a cost savings mode that prioritizes the home over the grid? I use cost savings and my house never runs off solar during peak.
 

RKCRLR

Member
Apr 13, 2020
434
168
Garden Valley, CA
Have you tried "balanced"? It tries to be self-powered in whenever practical. When it is charging the Powerwalls it will only take the excess so the you are not pulling or pushing to the grid (unless your off peak window is so small that it thinks it needs all of it to charge the PW for the peak period). You can use the "shoulder" (aka part peak) setting to bias when you want to it to use the batteries during real off peak hours if you want to fine tune it.

I've been running in balanced for a little while now it and it seems to do the job reasonably well.
I tried balanced but it will discharge the Powerwalls during off-peak which is not what I want.
 

Redhill_qik

Member
Aug 16, 2020
305
216
South SF Bay, California
Not hitting 100% charge would be my main concern about prioritizing the home during of-peak hours.
This will be highly dependent on house load during peak and the PV size. For my own personal situation, during the winter I encounter only 2 days where my PWs did not fully charge before Peak.

This should be the AI learned function that is Balanced. Understanding your house load during peak plus the expected weather and PV generation. My sprinkler system knows the weather and adjusts the watering timer, big data Tesla should be able to do the same.
 

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
I tried balanced but it will discharge the Powerwalls during off-peak which is not what I want.
For me, this is exactly what I want, use the PW's as much as possible. PW's only discharge until solar comes on line, then all they do is charge and wait until 3pm peak to run the house again 100%
 
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RKCRLR

Member
Apr 13, 2020
434
168
Garden Valley, CA
For me, this is exactly what I want, use the PW's as much as possible. PW's only discharge until solar comes on line, then all they do is charge and wait until 3pm peak to run the house again 100%
This does three things I don't like:

Depending on system size and conditions, it increases the likelihood that you won't hit 100% charge prior to peak rates. This may be compensated by the AI but I didn't stay on it long enough to find out.

It increases the likelihood that you won't have enough reserve if a power outage occurs. PG&E is unreliable in my area so this is important to me.

It increases the cycles on the Powerwalls and thus shortens their life. I'm in the camp that cycle life is the driving factor for Powerwall life and that the fewer cycles put on a Powerwall the longer it will last beyond warranty expiration.
 

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
This does three things I don't like:

Depending on system size and conditions, it increases the likelihood that you won't hit 100% charge prior to peak rates. This may be compensated by the AI but I didn't stay on it long enough to find out.

It increases the likelihood that you won't have enough reserve if a power outage occurs. PG&E is unreliable in my area so this is important to me.

It increases the cycles on the Powerwalls and thus shortens their life. I'm in the camp that cycle life is the driving factor for Powerwall life and that the fewer cycles put on a Powerwall the longer it will last beyond warranty expiration.
It has changed its behavior that it has hit 100% charge 100% of the time!!

This time of the year, who cares about power outage, solar will charge.

No proof on cycles, but again, for me, who cares, we have warranty. 10 years for electronics is they end up being replaced probably anyways.
 
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RKCRLR

Member
Apr 13, 2020
434
168
Garden Valley, CA
It has changed its behavior that it has hit 100% charge 100% of the time!!

This time of the year, who cares about power outage, solar will charge.

No proof on cycles, but again, for me, who cares, we have warranty. 10 years for electronics is they end up being replaced probably anyways.
This time of year you're probably right. But winter this isn't the case for me.

While there is currently no data on how long Powerwalls will last, it is a reasonable assumption that the Powerwall life will be similar to other lithium NMC chemistry batteries and thus life is driven by cycles. If an electronics board fails it can be replaced, and it is quite possible that the electronics don't fail. However, if the cycle life has been used up it probably wouldn't be cost effective to repair. I'm hoping to stretch the Powerwall life to match the 20 year NEM contract.
 

getakey

Active Member
Jan 28, 2020
1,321
429
95762
How does importing from the grid save you money while sending 100% of solar to recharging the PWs?

First, it is inefficient to be pulling from the grid from a remote source when the rooftop solar can be powering the house and recharging due to line losses.

Second, in CA you are incurring at least NBCs for the imported kWh during this period. The MDC of $0.32854/day gets you about 15 kWh of NBCs at no additional charge, but if/when NEM 3.0 drops the 100% credit for exports then the cost to import during the recharge will go up significantly making this mode even more desirable.

First priority is to make sure the PWs get to 100%. Thus solar should charge PWs until 100%. You are "banking" low cost kWhs into the PW. During peak, you want to power house from PW and send solar to grid at the Peak rates. That is where the cost savings occurs. You can control how much power is pulled from PW using reserve setting.
 

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
This time of year you're probably right. But winter this isn't the case for me.

While there is currently no data on how long Powerwalls will last, it is a reasonable assumption that the Powerwall life will be similar to other lithium NMC chemistry batteries and thus life is driven by cycles. If an electronics board fails it can be replaced, and it is quite possible that the electronics don't fail. However, if the cycle life has been used up it probably wouldn't be cost effective to repair. I'm hoping to stretch the Powerwall life to match the 20 year NEM contract.
I totally agree with Winter. Not sure what I will be doing, other than I guess adjusting the reserve amount up from the 10% I have now. Even so, was thinking last night, if I get a power outage, one of my battery banks is just for heating. I can live without that for a while. The other is just my house, and if we are smart, we can go a long time on these. And solar is not zero in the winter. Oh well, I always have my generator ready if all else fails.
 

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
First priority is to make sure the PWs get to 100%. Thus solar should charge PWs until 100%. You are "banking" low cost kWhs into the PW. During peak, you want to power house from PW and send solar to grid at the Peak rates. That is where the cost savings occurs. You can control how much power is pulled from PW using reserve setting.
My reserve 10%. Batteries low point is like 38% this morning. When it gets real hot, shall be interesting to see what happens.
 

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