Time Based Control Expected Behavior

[Steve2498]

I'm on a EV-A rate plan with Peak, Partial-Peak and off-Peak rates. When I use Time Based Control (TBC), the Powerwall is only discharging during the peak periods. In partial-peak and off-peak periods the house is always powered by the grid with any excess solar going to the PowerWalls or back to the grid. Is this expected behavior?

For the last few sunny days the PowerWalls have charged to 100% every day, so why not use the battery more during the partial-peak times? It is obviously great to not draw anything from the grid during peak, but why not also reduce grid use during partial-peak periods?

To get to what I think is better behavior, today I switched to Self Powered at 7AM, when partial-peak starts. That is eliminating grid use during partial-peak and it still looks like the batteries will get up to 100% so I'll be in good shape to continue no grid use during the peak period which starts at 2 PM.

I guess what I'd like to have is mode that eliminates grid use during peak as a priority, but then also eliminates partial-peak as much as possible when there is enough solar to keep the battery at a high SOC and then use the grid for any off-peak times.

Still trying to figure all this out.

 

[garrett5688]

Is this a new install? I think it’s recommended to set it and forget it so it learns usage patterns.

I’ve noticed that with the most recent update, where you can input more utility rate details, it seems to be working “smarter” for me. It used to discharge during off peak, to “make room” for future solar, which to me is idiotic. I haven’t noticed this recently, but it’s also winter so I don’t really have any “extra” energy for it to discharge.

What if you just give it 1 long peak period, and no partial peak?

 

[Steve2498]

It is a fairly new install, about 1 month. It is been in Time Based Control for nearly the entire time so I'd think it has had time to learn. There are still some start up things that haven't worked themselves out yet. I have the latest Tesla app but my ability to go off grid within the app still doesn't show up nor does the option to select the rate plan. I don't know how to get those features enabled. I know some of this takes time, like storm watch and vehicle charging when off grid weren't there at first but did show up a few days after the install.

Re: 1 long peak period and no partial peak. I've considered that. I'd lose the resolution of knowing how much energy was used during peak vs partial-peak, which perhaps in the long term doesn't matter. Like I said, still trying to figure all this out.

 

[dailo]

I am on the same plan and it is the expected behavior. With TOU it will always use grid during off peak and only use PW and send whatever solar is available back to the grid. You can customize the plan and change the hours for off peak and on peak so that you can utilize your powerwall more. When I had more solar production it did sometimes use solar to offset my grid usage and use the remainder for charging, so maybe there is some algorithm that figures out if it can charge the battery before peak starts but I’m not sure.

 

[tomuo]

Time based control did poorly for me yesterday.
On days with no cloud, PW reaches 100% by noon, so the algorithm does self-powered from 9am till full (good & smart).
But yesterday there was cloud all day, so it was still doing self-powered from around 9am and only got to around 80% by the time we switch to peak TOU(4pm), but overall we'd had enough solar to go to 100% PW otherwise.
My guess is that it looks at the previous day's usage (or average over several days) to know when to do self-powered.

I was hoping it could look at the weather forecast and know that on that day it should prioritize charging.
On these days, we're more likely to need to run the heat pump heating during peak as well, so it would be nicer to have a mode for "priority charge PW".

 

[Steve2498]

Time based control did poorly for me yesterday.
On days with no cloud, PW reaches 100% by noon, so the algorithm does self-powered from 9am till full (good & smart).
But yesterday there was cloud all day, so it was still doing self-powered from around 9am and only got to around 80% by the time we switch to peak TOU(4pm), but overall we'd had enough solar to go to 100% PW otherwise.
My guess is that it looks at the previous day's usage (or average over several days) to know when to do self-powered.

I was hoping it could look at the weather forecast and know that on that day it should prioritize charging.
On these days, we're more likely to need to run the heat pump heating during peak as well, so it would be nicer to have a mode for "priority charge PW".

I think I’ve devised a plan that might model the behavior I’m looking for, which is to only use the grid in off peak periods.

1st, this assumes solar production is enough to recharge the batteries to 100% before reaching the peak period (for me that is 2PM). Which on sunny January days it is currently doing. For the past few weeks, if I start the peak period at 100%, at the end of the peak, when the TOU algorithm goes back to using the grid, the batteries are between 80% and 85%. Then the next day solar gets the battery back to 100% by noon.

So,I’m going to try This:

Start the day off at 7 AM (start of partial peak) with battery >= 80%
Use Self powered mode
Set the reserve to 80%

Based on what I see from today, I’ll be using the battery From 7AM, solar will charge the battery to 100% by noon while also powering the house. The battery will discharge to 80% some time after 9PM when I’m back to a partial peak rate but likely before 11PM, when I’m back to an off peak rate. The grid would then power the house until 7AM the next day. All with no changes needed in the app.

Of course as soon as I have one or more low solar production day(s) I’d have to manually change things.

 

[aesculus]

My guess is that it looks at the previous day's usage (or average over several days) to know when to do self-powered.

I was hoping it could look at the weather forecast and know that on that day it should prioritize charging.
On these days, we're more likely to need to run the heat pump heating during peak as well, so it would be nicer to have a mode for "priority charge PW".

No weather is used. It does use what it saw in days prior, so when weather changes it can make a big difference, especially it was sunny and then it's not on following days.

Also Fridays and sometimes Thursdays are the worst for the correct balance of charging and discharging because it may decide based on recent experience it could do better by sending power back in partial peak vs saving it in the PW for peak, thinking you won't need it for an upcoming rate change on the weekend. But then you find out the next day your solar production is less that before or your usage went up, and you are forced to by peak power when your PWs hit your reserve.

 

[jjrandorin]

OP you likely should be reading through this thread:

Tesla App Utility plan configuration: Multiple Peaks, Buy/Sell Behavior, etc

Starting a thread to document behavior I'm seeing using the new multiple peaks configurations (really multiple of any type). Maybe this information exists elsewhere but I couldn't find it when I first had my system go live a couple years ago, and I'm not really seeing if for the multiple peak...

teslamotorsclub.com

To look at trying to fine tune it to do what you want. You can likely get it to do what you want, by setting up schedules that do what you want (see the above thread for discussion on this from people who fine tune this).

Regular time based control just discharges during peak, from what I understand. I use self powered mode so dont have direct pointers myself but people in the above thread are talking about the new configuration abilities etc.

 

[MY2021f]

If it doesn't think you're going to make it through peak time then it won't use the powerwall during partial peak. And if your partial peak charge isn't much more than off peak then it won't use it either, because it's not worth the efficiency losses.

 

[NikoV6]

My TBC seems to have worked out we really do need full charge every day during winter as our ASHP comes on from 04:30 to heat the house and can deplete the PW to about 30% before the sun shines (long story, old cottage that needs serious insulation work!)

My problem is that on a nice sunny day like today, in TBC not all solar goes into battery to recharge, often some is going back to grid. I do not have FIT and cant get SEG as I DIY installed my system (stupid MCS requirement for SEG!)

Solution is to switch to self powered and then all generation up to 5Kw goes to battery. If I forget to switch it back however, no overnight charge!

So, can I add to the TBC wish list, can we have an export slider as well please! So I can set it to never export if batteries need charging.

Obviously, excess solar over the 5Kw charge rate of the battery and any the house is using should still go to the grid, we throttle ours to a max export of 3.6Kw DNO requirement using G100 compliant inverter and CT

 

[BGbreeder]

If you browse around here, I think that you may see that many of us have found that playing with the pricing table in the utility rate section nudges the TEG to the desired behavior. E.g. lower the value for the exported power during the morning/midday, and make the grid charge window overnight very low. I found that adding slightly more than the expected efficiency loss causes the algorithm in the TEG not to export during my off peak rate and fill the powerwall and then export during mid-peak rates, and power the house during peak rates.

All the best,

BG