Advanced: Cost Saving Hack to maintain PW2 at peak capacity

[NinjaVece]

Most folks that are under Time Of Use (TOU) pricing either voluntarily or as NEM 2.0 customers especially in California, will use the Powerwall 2 (PW2) in Advanced: Cost Saving mode.

Weekday settings accessible behind the 'Edit Price Schedule' button in the 'Customize' portion of the iPhone or Android app when Advanced is check-marked is fairly straight-forward. Simply set up any Off-Peak, Shoulder-Peak and Peak timeframes (and set the Reserve level you wish to allow the PW2 to drop to before reaching Standby) and the PW2 will automatically recharge the PW2 each morning through Off-Peak and Shoulder-Peak periods. It will then discharge during Peak periods to the Reserve level and the cycle begins again the next day.

Weekend settings, however, do not function as Weekday setting do under even the most current firmware release (I currently have 1.24.0 but this bug has been around for a long time).

Most grid providers either ONLY have Off-Peak periods for weekends OR they have a combination of Off-Peak and Shoulder-Peak periods. For those only with Off-Peak periods, this can be set with the 'All Day Off-Peak' toggle or by manually setting up the Off-Peak timeframe in the graph for the entire day.

During the weekend, the PW2 will NOT recharge during any Shoulder-Peak periods OR if there is only Off-Peak in the settings (either through the toggle or manual setup). This is a known bug which prevents the PW2 from recharging from Friday's usage on Saturday morning and relegates the PW2 to the Reserve level reached on Friday afternoon all through the weekend and into Monday morning until the PW2 recharges that day.

In order to, instead, force the PW2 to recharge on Saturday morning so that the PW2 is 100% charged over the weekend, a 'hack' must be employed for the Weekend setting.

Simply set the Off-Peak period from 9pm to 8:30pm (23.5 hours) and set the Shoulder-Peak period from 8:30pm to 9pm. When the PW2 sees the tiny Shoulder-Peak period, it will allow the battery to recharge throughout the day to the 100% level. The tiny half hour period at night will discharge the battery maybe 5% which will quickly be recharged Sunday morning and again Monday morning (as the half hour period would also apply to Sunday night).

The reason for the 8:30pm to 9pm Shoulder-Peak period versus even later at night is for those who actually do have a Shoulder-Peak on the weekend - which usually lasts till 10pm (SCE for example with their TOU plan). That way, if you have, for example a Tesla that you charge at night and Off-Peak begins at 10pm so you defer the charging to that time, the battery isn't discharging when you are using a lot of power - as grid power is cheaper during Off-Peak.

This solution should suffice for anyone that wants to make sure their PW2 is fully charged between Saturday and Monday while using Advanced: Cost Saving mode.

Here is a pic of the setting as I have it:

 

[miimura]

Balanced mode will charge to full during a completely Off-Peak weekend. It will not discharge during Off-Peak. I am very happy with Balanced mode on the PG&E EV rate plan.

 

[NinjaVece]

Balanced mode will charge to full during a completely Off-Peak weekend. It will not discharge during Off-Peak. I am very happy with Balanced mode on the PG&E EV rate plan.

Just a question regarding Balanced mode. Are you seeing your PW2 discharge at night?

Powerwall Modes with Solar | Tesla Support

'Use stored solar power to power your home when electricity is expensive and after the sun goes down'

Let me know if that is the case for you. For a person under TOU pricing, discharging of the battery at night is a complete waste.

 

[miimura]

Just a question regarding Balanced mode. Are you seeing your PW2 discharge at night?

Powerwall Modes with Solar | Tesla Support

'Use stored solar power to power your home when electricity is expensive and after the sun goes down'

Let me know if that is the case for you. For a person under TOU pricing, discharging of the battery at night is a complete waste.

My system NEVER discharges during Off-Peak. Period. It may or may not continue discharging during the Part-Peak period 9pm-11pm on weeknights, depending on SOC and other factors. It will pretty much always discharge during Part-Peak on Friday nights because so much of Saturday is Off-Peak and that battery energy can be replaced with low cost Off-Peak generation.

Here is yesterday and today's charts as an example. There was a power outage from 6:25-7:26am so that's why there was discharge during that time. I plugged in both my cars at 9:15pm and there was a 4 minute draw while the JuicePlug connected to the internet and the Powerwalls did discharge to offset that. When the JuicePlug told the car to start charging at 11:00pm the Powerwalls were in Standby and the car charged from cheap Off-Peak grid energy. Coincidentally, the RAV finished charging and the Model 3 started at 2am.

 

[MorrisonHiker]

Just a question regarding Balanced mode. Are you seeing your PW2 discharge at night?

Powerwall Modes with Solar | Tesla Support

'Use stored solar power to power your home when electricity is expensive and after the sun goes down'

Let me know if that is the case for you. For a person under TOU pricing, discharging of the battery at night is a complete waste.

I only tried it one night so far but didn't see the Powerwalls discharge at all during off-peak period.

I don't know if it is a complete waste. If I could use 0 kWh from the grid vs. using the Powerwalls to power my house, wouldn't I want to do that? I was nearly 100% self-powered for the two weeks before I got TBC. When I tried TBC, that dropped to 80%. I guess it does cause more wear and tear on the Powerwalls. Perhaps as a cost/benefit analysis, it costs more to use the Powerwalls but at least it's all clean energy that I'm using.

I'm still trying to figure out if I should use TBC or Self-powered. We have a large solar system with Powerwalls that can cover almost all our usage. Our peak period is only 4 hours long and we probably only use 6 kWh during peak on a typical day so that can easily be covered by the Powerwalls. We are on TOU but we would've only gotten a measly 1.5 cents per kWh if we sold power back to the grid so that didn't make much sense. We opted for the kWh bank instead so that generation in the summer will be able to offset winter usage.

So my options are Self-powered and use virtually no grid power or TBC and use a lot more grid power than Self-powered mode. Maybe I should start a different thread...or do you know if there's another one that already discusses these two options?

 

[miimura]

Whether you want to use TBC or Self Powered really depends on your solar generation relative to your usage. It also depends on your rate structure. I have a relatively small array. It would only offset my household usage and can't cover my EV charging, so I use TBC to get the maximum net metering credit for my Peak period generation. That allows be to buy more Off-Peak energy for EV charging. Before Powerwalls, I was paying about $1,000 per year for my net metered usage. It should be less than half that the first year with the Powerwalls.

 

[NinjaVece]

My system NEVER discharges during Off-Peak. Period. It may or may not continue discharging during the Part-Peak period 9pm-11pm on weeknights, depending on SOC and other factors. It will pretty much always discharge during Part-Peak on Friday nights because so much of Saturday is Off-Peak and that battery energy can be replaced with low cost Off-Peak generation.

Here is yesterday and today's charts as an example. There was a power outage from 6:25-7:26am so that's why there was discharge during that time. I plugged in both my cars at 9:15pm and there was a 4 minute draw while the JuicePlug connected to the internet and the Powerwalls did discharge to offset that. When the JuicePlug told the car to start charging at 11:00pm the Powerwalls were in Standby and the car charged from cheap Off-Peak grid energy. Coincidentally, the RAV finished charging and the Model 3 started at 2am.

View attachment 338896 View attachment 338899

Miimura, I'm seeing your Powerwall discharge on your first photo after the Peak period - I'm assuming until it reaches Reserve level. That is EXACTLY what I'm trying to avoid.

There is very little value in the PW2 battery discharging during Shoulder-Peak price-wise (for most installations) and it removes coverage your battery might have extra during a real outage.

Do you see what I'm seeing? This is the reason I stay with Cost Saving - it is not supposed to discharge during Shoulder-Peak periods. The error is that on weekends, it will - thus my hack.

 

[dswansonsb]

Miimura, I'm seeing your Powerwall discharge on your first photo after the Peak period - I'm assuming until it reaches Reserve level. That is EXACTLY what I'm trying to avoid.

Couldn't you simplify configure only peak and off-peak times (no shoulder)?

 

[cwied]

Couldn't you simplify configure only peak and off-peak times (no shoulder)?

I think the goal would be to be able to configure time periods for charging, standby and discharging. Off-peak is charging, peak is discharging and the closest to standby is shoulder. There are times when you want to leave the battery at a low SoC to make room for charging later. I don't think you can do this without shoulder periods.

 

[miimura]

Miimura, I'm seeing your Powerwall discharge on your first photo after the Peak period - I'm assuming until it reaches Reserve level. That is EXACTLY what I'm trying to avoid.

There is very little value in the PW2 battery discharging during Shoulder-Peak price-wise (for most installations) and it removes coverage your battery might have extra during a real outage.

Do you see what I'm seeing? This is the reason I stay with Cost Saving - it is not supposed to discharge during Shoulder-Peak periods. The error is that on weekends, it will - thus my hack.

Yes, depending on SOC, my system does discharge during the shoulder-peak evening period. I have two Powerwalls and currently have the Reserve set at 25%. It has never hit that reserve. IIRC, I changed it from 50% to 25% around June. I will change it back to 50% when the weather turns bad or my generation drops to 50% of the peak summer level, which would be about 12.5kWh/day, or a little less than one PW worth.

This is my way of looking at it.
1. My generation happens during Shoulder or On-Peak periods. Therefore, the value of the solar is the same as the shoulder-peak rate.
2. I never want it to give away that value by discharging during Off-Peak, which it obeys.
3. Because I have NEM 1.0 Net Metering, discharging during shoulder-peak is only cycling the battery more, it doesn't cost me anything.
4. Discharging during shoulder-peak can make me money if the battery energy is replaced with weekend Off-Peak generation.

So, I am satisfied with the way my system is working in Balanced Mode. The two charts I posted above are from Thursday and Friday. That small amount of discharge during the evening Part-Peak period will be made up during the weekend Off-Peak generation, so it will actually make me a little bit of money if the clouds would bugger off. Today's production was only 11.1kWh while Monday's was over 16kWh.

 

[NinjaVece]

Couldn't you simplify configure only peak and off-peak times (no shoulder)?

The effect would be the same.

 

[NinjaVece]

Yes, depending on SOC, my system does discharge during the shoulder-peak evening period. I have two Powerwalls and currently have the Reserve set at 25%. It has never hit that reserve. IIRC, I changed it from 50% to 25% around June. I will change it back to 50% when the weather turns bad or my generation drops to 50% of the peak summer level, which would be about 12.5kWh/day, or a little less than one PW worth.

This is my way of looking at it.
1. My generation happens during Shoulder or On-Peak periods. Therefore, the value of the solar is the same as the shoulder-peak rate.
2. I never want it to give away that value by discharging during Off-Peak, which it obeys.
3. Because I have NEM 1.0 Net Metering, discharging during shoulder-peak is only cycling the battery more, it doesn't cost me anything.
4. Discharging during shoulder-peak can make me money if the battery energy is replaced with weekend Off-Peak generation.

So, I am satisfied with the way my system is working in Balanced Mode. The two charts I posted above are from Thursday and Friday. That small amount of discharge during the evening Part-Peak period will be made up during the weekend Off-Peak generation, so it will actually make me a little bit of money if the clouds would bugger off. Today's production was only 11.1kWh while Monday's was over 16kWh.

The way a PW2 can pay for itself is in the savings it accrues for you under TOU. I, too, am an NEM 1.0 customer, but after I accrue data through my grid operator (SCE) for a few more months using the PW2 as if I was under TOU, I will have a better picture if the PW2 will save me significant money going to that arrangement.

Thus, the reason for my hack. I'm trying to keep the PW2 to ONLY discharging during Peak periods to see if it will save me money off my SCE bill in the long run.

 

[miimura]

I can definitely see the difference in my bills due to Powerwall allowing max export during Peak hours. I used to use almost all my Peak Period generation after the sun went down. Now I can see significant net export during the Peak period on my bills. I should do a bar chart comparison of each TOU period Apr-Sept 2017 vs. 2018.

 

[power.saver]

The way a PW2 can pay for itself is in the savings it accrues for you under TOU. I, too, am an NEM 1.0 customer, but after I accrue data through my grid operator (SCE) for a few more months using the PW2 as if I was under TOU, I will have a better picture if the PW2 will save me significant money going to that arrangement.

Thus, the reason for my hack. I'm trying to keep the PW2 to ONLY discharging during Peak periods to see if it will save me money off my SCE bill in the long run.

It will save you money, because you won't have any peak draw, and will instead export excess or all solar during the peak. In fact, TOU-D-A with just solar is better than tiered rates, the PW with TBC only makes it better.

SCE just changed over to winter season, so the price difference between shoulder and peak is only 5c/kWh and the savings will be less than what it is in the summer with a 14c/kWh difference. Next month Daylight Saving Time ends, so there will be less useable sunlight in the peak period (probably just 2 hours from 2pm to 4pm).

 

[MITE46]

Thanks! I was wondering why my PWs were not charging from the grid during off peak weekends

 

[NinjaVece]

It will save you money, because you won't have any peak draw, and will instead export excess or all solar during the peak. In fact, TOU-D-A with just solar is better than tiered rates, the PW with TBC only makes it better.

SCE just changed over to winter season, so the price difference between shoulder and peak is only 5c/kWh and the savings will be less than what it is in the summer with a 14c/kWh difference. Next month Daylight Saving Time ends, so there will be less useable sunlight in the peak period (probably just 2 hours from 2pm to 4pm).

SCE winter rates are actually 7c/kWh difference between Shoulder-Peak and Peak (27c/35c).

Time-Of-Use Residential Rate Plans | Rates | Your Home | Home - SCE

Otherwise, I agree completely.

 

[NinjaVece]

Thanks! I was wondering why my PWs were not charging from the grid during off peak weekends

Most welcome. The PW2 bug is that, under Advanced: Cost Saving, it treats Shoulder-Peak differently on the Weekend setting than on the Weekday setting. On Weekdays, it defaults to only discharging during Peak and recharging during Off-Peak and Shoulder-Peak. On Weekends, when there is no Peak, it treats the Shoulder-Peak as a period it cannot recharge the battery - only Off-Peak periods can recharge and they are usually during low-light or night hours so do nothing to recharge your PW2. Finally, if you ONLY have Off-Peak, it simply doesn't recharge at all on Weekends.

Thus the hack to trick the PW2 into recharging on the weekends, while only allowing for a small half hour discharge late at night. Remember, if you do use any appliances during true Off-Peak periods (under SCE this is 10pm to 8am) to get the lowest cost grid power (I have a Model 3 I charge at that time), don't have that short half-hour Shoulder-Peak period during those times. This will drain the PW2 just when you want to use grid power. Thus, the reason I set Shoulder-Peak between 8:30-9pm.

If Tesla fixes this error, you can likely go back to specifying exactly how your grid operator has set up their Weekend settings. Until then, this is a simple fix.

 

[Frankman60]

I am getting ready for 2 PWs to be installed later this year and am trying to relate the “Hack” by NinjaVece to my SDG&E TOU periods. Peak is 4 to 9 PM every day of the week. However, the Off Peak time periods are different on weekdays and weekends. Off Peak is 12 AM to 6 AM weekdays, and 12AM to 2 PM weekends. The PWs have more than enough capacity to fully cover all of our Peak period usage so all solar generation during Peak should be exported to the grid. I would prefer that the PWs do not discharge at all during Off Peak. Will the “hack” be necessary to do this or can I just run the Balanced or Cost Savings TBC profiles?

 

[MorrisonHiker]

I am getting ready for 2 PWs to be installed later this year and am trying to relate the “Hack” by NinjaVece to my SDG&E TOU periods. Peak is 4 to 9 PM every day of the week. However, the Off Peak time periods are different on weekdays and weekends. Off Peak is 12 AM to 6 AM weekdays, and 12AM to 2 PM weekends. The PWs have more than enough capacity to fully cover all of our Peak period usage so all solar generation during Peak should be exported to the grid. I would prefer that the PWs do not discharge at all during Off Peak. Will the “hack” be necessary to do this or can I just run the Balanced or Cost Savings TBC profiles?

Based on what I've seen, that's how it works. By default, they seem to only discharge during peek and part-peak. Mine aren't discharging at all in off-peak. Since I actually wanted them to discharge, I actually had to extend my part-peak times.

 

[power.saver]

You won't need this since you have a peak period every day. It's only necessary for those of us that don't have a peak period on the weekend and want to force the PW to charge when it otherwise wouldn't.