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Newbee Question on App Display/Settings

getakey

Active Member
Jan 28, 2020
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thats not what it is supposed to do at least under Cost Savings. During off peak, all solar should be going to PW.
What setting would change that?
 

miimura

Well-Known Member
Aug 21, 2013
6,254
5,878
Los Altos, CA
thats not what it is supposed to do at least under Cost Savings. During off peak, all solar should be going to PW.
What setting would change that?
Mine varies between "all solar" and "surplus solar" when in Balanced Mode. To me, if you have sufficient solar production, there is no point to charging faster to 100% just to go into Standby and let the surplus solar go to the grid before the Off-Peak period ends. With grid rules like NEM 2.0 that has Non-Bypassable Charges, it is beneficial to self-consume some of the solar so that you don't pay NBCs for those kWh during production hours.
 

miimura

Well-Known Member
Aug 21, 2013
6,254
5,878
Los Altos, CA
Example chart. In the morning it charges from All Solar and then when it has enough to predict 100% SOC by the end of Off-Peak, it only charges from Surplus Solar. Then during Part-Peak from 3p-4p it exports Surplus Solar and during Peak 4p-9p it exports All Solar. It continues to mostly power the house from PWs throught Part-Peak 9p-12mid.

2020-07-23r.jpg
 
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getakey

Active Member
Jan 28, 2020
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seems to me the priority should be to make sure PW is 100% prior to peak. Looking at the graph with the negative spikes, it isn't obvious that this would always be the case with that behavor.
 

getakey

Active Member
Jan 28, 2020
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Mine varies between "all solar" and "surplus solar" when in Balanced Mode. To me, if you have sufficient solar production, there is no point to charging faster to 100% just to go into Standby and let the surplus solar go to the grid before the Off-Peak period ends. With grid rules like NEM 2.0 that has Non-Bypassable Charges, it is beneficial to self-consume some of the solar so that you don't pay NBCs for those kWh during production hours.

But if the PW is going to get to 100%, doesn't matter if you charge it fast or slow. Same amount of power goes the the wall. Rest of the solar will power house and go to grid. As long as PW gets to 100% it doesn't matter if you stretch it out or do it as fast as you can, My concern would be in the stretch out scenario, you mat not get to 100%. What if cloud cover comes in the afternoon?
 

miimura

Well-Known Member
Aug 21, 2013
6,254
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Los Altos, CA
But if the PW is going to get to 100%, doesn't matter if you charge it fast or slow. Same amount of power goes the the wall. Rest of the solar will power house and go to grid. As long as PW gets to 100% it doesn't matter if you stretch it out or do it as fast as you can, My concern would be in the stretch out scenario, you mat not get to 100%. What if cloud cover comes in the afternoon?
It does matter if you have NBCs or your feed-in to the grid is reimbursed less than your retail consumption rate. Once you take power from the grid to allow your PWs to charge faster, you have already taken it. Once you hit 100%, you have to let the solar go to the grid. In PG&E territory, these fine points are not really consequential because we're only talking about a couple cents per kWh or less.
What about cloud cover? The PWs can always go back to charging from All Solar if it's not on track to hit 100%. Also, getting all the way to 100% may not matter as long as it gets pretty close.
 

bob_p

Active Member
Apr 5, 2012
3,691
2,801
Cost Savings mode appears to have a bug - it should reduce the electricity usage in the peak mode as much as possible.

We are under a FREE NIGHTS plan (free from 9PM to 9AM).

The TEG should not use any PowerWall energy during the Off-Peak period - and if there's excess during the Peak period, it is sent to the grid.

But that's not what's happening. The TEG is using PW energy overnight, sometimes dropping us well below our Reserve % (which is set at 30%) - I've seen the charge level drop close to 20% before the panels start getting solar power.

This must be a bug - because unless the grid is down, the system should not draw power from the PW below the Reserve %.

As a temporary workaround - a Tesla owner has published a Samsung Smart Things app that will automatically change the settings on a schedule. I tried it out, putting the system in Cost Savings mode between 9AM to 9PM and then in Backup Mode (with 100% reserve) between 9PM to 9AM, and that stopped the power draw from the PW overnight. The downside of doing this is that I lose the daily, weekly, monthly reporting in the Tesla app on the Peak vs. Off-Peak power usage.
 

miimura

Well-Known Member
Aug 21, 2013
6,254
5,878
Los Altos, CA
I get the NBCs
But if you don't get to 100%, NBC is trivial
Not getting to 100% only matters if you routinely use up all the energy down to your Reserve. This time of year, my Reserve is set to 25% and my Powerwalls never go below 50%, even when they power the house from 4pm to midnight.
 

miimura

Well-Known Member
Aug 21, 2013
6,254
5,878
Los Altos, CA
Cost Savings mode appears to have a bug - it should reduce the electricity usage in the peak mode as much as possible.

We are under a FREE NIGHTS plan (free from 9PM to 9AM).

The TEG should not use any PowerWall energy during the Off-Peak period - and if there's excess during the Peak period, it is sent to the grid.

But that's not what's happening. The TEG is using PW energy overnight, sometimes dropping us well below our Reserve % (which is set at 30%) - I've seen the charge level drop close to 20% before the panels start getting solar power.

This must be a bug - because unless the grid is down, the system should not draw power from the PW below the Reserve %.
Agree. It should not discharge below the Reserve.

I really wish there was a button for "Never Discharge during Off-Peak".
 
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getakey

Active Member
Jan 28, 2020
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Not getting to 100% only matters if you routinely use up all the energy down to your Reserve. This time of year, my Reserve is set to 25% and my Powerwalls never go below 50%, even when they power the house from 4pm to midnight.

I'm still on a 2pm to 9pm Peak. I have Reserve set at 30%. We are east of Sacramento and much hotter than you. If it gets above 95, I cannot make it all the way to 9pm. For the last 2 weeks or so we have been over 95. Usually runs out about 7:30pm
 

miimura

Well-Known Member
Aug 21, 2013
6,254
5,878
Los Altos, CA
I'm still on a 2pm to 9pm Peak. I have Reserve set at 30%. We are east of Sacramento and much hotter than you. If it gets above 95, I cannot make it all the way to 9pm. For the last 2 weeks or so we have been over 95. Usually runs out about 7:30pm
Sounds like you either need to do pre-cooling before Peak hours or you need more Powerwalls.
 

getakey

Active Member
Jan 28, 2020
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406
95762
I could change my reserve to make it through, but I want to keep at 30%. I have 3 PWs. I also have a whole house fan and house is well insulated. It just gets hot here and house is 4000 sq ft
 

TheDon

Member
Jun 26, 2019
62
7
Southern California
thats not what it is supposed to do at least under Cost Savings. During off peak, all solar should be going to PW.
What setting would change that?

I am using the Balanced setting which is a bit different than Cost Savings. In my case, I can use the battery from 1600-2100 (peak time) and it will continue to use it through the night. It depends on the algorithm that they use and SOC. When the sun comes up, it powers back up the battery and powers the house. If it cools down so I don't use AC, it will fill the battery to 100% before noon. If I use AC, it takes till 1230 to fill the battery.

To address the initial issue, the numbers on the App now makes sense and are very close to the raw data downloaded. (Within rounding error from Teslas' database.) The old days are still wrong but I have the raw data to do calculations on.

In cost savings, the behavior is "Powerwall will charge from excess solar during off-peak and shoulder (if required).
Powerwall will discharge during peak and discharge in other periods to ‘make room’ for solar based on energy forecast."

It differs for Balanced in it says "Powerwall will discharge during all periods, minimizing exports during shoulder and off-peak." So if you have free times, balanced will be sure not to export power to the grid for free. Mine costs something no matter when so exporting at peak ($0.41kWh) and non-prime ($0.15kWh) helps reduce costs. That's why I do the calculations to be sure I get more $$$ credit than I do to purchase from them.

The last time I charged my M3 it costs about $0.32 to purchase energy from Edison.
 

getakey

Active Member
Jan 28, 2020
1,237
406
95762
In cost-savings, it doesn't use excess solar, it uses all the solar during off peak until fully charged.
I removed all shoulder time so that PW only discharges during Peak. I didn't like the predictive algorithyms.
 

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