PW TOU Price Settings for Buy & Sell

[Mayer]

What parameters are reasonable to enter into settings for buy/sell behavior?
I’m not necessarily looking to maximize return but rather avoid blocking buy/sell with matching amounts for buy/sell.
Image shows current setting: my TOU rates, and my buy/sell parameters, all match.
Is this a reasonable setup?
Or am I canceling out any buy/sell by making it match?

 

[BGbreeder]

@Mayer you might get better answers if folks knew your utility/locale...

 

[Mayer]

@Mayer you might get better answers if folks knew your utility/locale...

Thank you @BGbreeder
Southeastern Pennsylvania
PECO

 

[miimura]

If you have 1:1 net metering then it makes sense to set the buy and sell equal.

I was just converted to NEM2 from NEM1 because I expanded my solar array. NEM1 has 1:1 net metering and I used equal Buy and Sell pricing. Now that I am on NEM2, I pay a small "Non-Bypassable" charge for each kWh taken from the grid. What this means is that if you use a lot of energy from the grid outside of solar hours and then turn around and export a lot, you will have significant minimum charges that won't be offset by your export credits. Therefore, I set the Sell price to be smaller than the Buy price by the amount of the Non-Bypassable Charge plus 10% for round trip losses.

My Off-Peak Buy is $0.35 and Off-Peak Sell is $0.28. When there is sufficient solar generation, this encourages the Powerwall system to charge only with surplus solar. However, in the Winter when there is not enough solar, it continues to supply the house from the grid while all solar goes to charge the batteries. The most important thing is to have enough energy to make it through the higher rate periods on battery energy. The NBCs are a lesser concern.

 

[RKCRLR]

If you have 1-1 net metering and no non-bypassable charges then your best financial option is to not use your Powerwalls for anything other than backup power during outages.

 

[Jeremy3292]

Similar questions for me.

My issue is I have TOU periods (on/off peak/super off peak) with monthly netting within each TOU period. The monthly netting gives me an effective 1:1 net metering, but only when solar can offset the grid usage.

Super Off Peak (12am-6am spring/summer/fall only): Buy $0.08 Sell $0.08
On Peak (weekdays only, 6-9pm spring/summer/fall + 6-9am winter): Buy $0.20 Sell $0.20
Off Peak (all other times): Buy $0.11 Sell $0.11

However, any excess energy exported within each TOU period is credited at only $0.04 per kWh, the utility's alleged avoided cost of electricity. So as you can see the only times I will be generating solar is during the off peak period (unless I export PW stored energy).

How would I set this up in the Tesla app? I obviously do not want to use my PW's at any time other than the peak period(s) and I would want my car charging to be done from the grid/solar without pulling from the PW's.

My best guess is leave the off peak at the same buy/sell ratio of $0.11, set up on peak at something ridiculous like $1.00 buy and $0.01 sell, and then for the super off peak period maybe just deal with whatever energy the house uses while asleep?

 

[Mayer]

If you have 1-1 net metering and no non-bypassable charges then your best financial option is to not use your Powerwalls for anything other than backup power during outages.

I have TOU option with price for peak hours (2-6 PM) substantially higher than off peak.

So my PW automatically draws down during peak hours and charges from the grid during off peak hours.

I believe I have 1-1 Net Metering through PECO (Pennsylvania) but with TOU rates, it still makes sense to draw from PW during peak hours and sell the solar production to the grid?

If so, should Sell and Buy pricing match each other, and match the TOU pricing from PECO?

 

[RKCRLR]

I have TOU option with price for peak hours (2-6 PM) substantially higher than off peak.

So my PW automatically draws down during peak hours and charges from the grid during off peak hours.

I believe I have 1-1 Net Metering through PECO (Pennsylvania) but with TOU rates, it still makes sense to draw from PW during peak hours and sell the solar production to the grid?

If so, should Sell and Buy pricing match each other, and match the TOU pricing from PECO?

Yea, I forgot to mention TOU (brain fart). If you have TOU then there is a good reason to use the powerwalls.

 

[Mayer]

However, any excess energy exported within each TOU period is credited at only $0.04 per kWh, the utility's alleged avoided cost of electricity.

I wondered what compensation is given from PECO for solar produced and transferred to the grid during peak hours.

So PECO likely draws from my Solar during peak hours but only pays me off peak rates?

 

[Mayer]

My best guess is leave the off peak at the same buy/sell ratio of $0.11, set up on peak at something ridiculous like $1.00 buy and $0.01 sell, and then for the super off peak period maybe just deal with whatever energy the house uses while asleep?

It’s confusing.
If your correct that you can stop your system from drawing from grid during peak times by adjusting buy/sell prices, what happens when you set your sell price above what utility carrier will pay.

Your extra solar must go someplace or your system shuts down.

I have a feeling this arbitrage idea of setting your buy/sell price is B.S.

The utility company sets the price.

At best we control what we are willing to sell from the small amount of stored energy in our PW(s) during peak hours and, if set too high, there will be no draw from power wall to grid, and only excess solar will go to grid, but at what price or credit?

Conclusion: 1 to 1 net metering is confusing when layered onto TOU fluctuations

Conclusion: PW Arbitrage is mostly BS

 

[BGbreeder]

It’s confusing.
If your correct that you can stop your system from drawing from grid during peak times by adjusting buy/sell prices, what happens when you set your sell price above what utility carrier will pay.

Your extra solar must go someplace or your system shuts down.

I have a feeling this arbitrage idea of setting your buy/sell price is B.S.

The utility company sets the price.

At best we control what we are willing to sell from the small amount of stored energy in our PW(s) during peak hours and, if set too high, there will be no draw from power wall to grid, and only excess solar will go to grid, but at what price or credit?

Conclusion: 1 to 1 net metering is confusing when layered onto TOU fluctuations

Conclusion: PW Arbitrage is mostly BS

Setting the pricing to different values is just to influence the Powerwall/gateway to do what you want at the times that you want. Because, we, like @miimura have NBCs, I adjust the pricing to account for the cost of imports, and for the inefficiency of using solar to charge the Powerwalls, rather than direct export. California rates have some other wrinkles that can make NBCs better under certain conditions, e.g. net power exporter annually. @RKCRLR has posted extensively on this.

When we had 1:1 net metering with TOU, I just made sure that there was at least a 10% difference in the buy/sell price. The powerwalls then did what I wanted which was covering peak power rates.

All the best,

BG

 

[Mayer]

Setting the pricing to different values is just to influence the Powerwall/gateway to do what you want at the times that you want.

This adds clarity.

And yes, I’d just like PWs to power house during peaks, and be left fully charged during all off peak hours.

Right now PW is still being depleted off peak, like on weekends, for no reason which reduces backup in case of outage.

It would be better if we could completely eliminate access to PW before and after peak hours.
I guess adjustments to buy/sell pricing is the work around.

 

[Jeremy3292]

When we had 1:1 net metering with TOU, I just made sure that there was at least a 10% difference in the buy/sell price. The powerwalls then did what I wanted which was covering peak power rates.

Buy/sell price 10% difference in the same TOU period? Meaning like buy $0.10 and sell $0.09 per kWh? Any advice on how to prevent powerwall usage when charging your car? Use grid/solar only.

 

[miimura]

Buy/sell price 10% difference in the same TOU period? Meaning like buy $0.10 and sell $0.09 per kWh? Any advice on how to prevent powerwall usage when charging your car? Use grid/solar only.

Yes, that price difference is what we’re talking about.
I use Time Based Control to prevent Powerwall usage while charging my car. The cars are both set to charge between midnight and 8am. The Powerwalls never discharge during that Off-Peak period. If I want to use surplus solar to charge the Tesla, I use the “Charge on Solar” feature. In order to ensure that it only uses Surplus Solar I only turn on the feature after the Powerwalls are above 95%. Then the car will soak up the afternoon solar until the rates go up. Then it will automatically stop.
If you want to charge a non-Tesla EV with surplus solar you have to use an EVSE that has that feature. Emporia is supposed to have it but I have not looked into the details. Zappi is famous for this feature outside North America.

 

[Mayer]

Buy/sell price 10% difference in the same TOU period? Meaning like buy $0.10 and sell $0.09 per kWh? Any advice on how to prevent powerwall usage when charging your car? Use grid/solar only.

I was wondering how to apply 10% guideline suggested by @BGbreeder too.

Regarding how to stop PW useage whike charging EV, I just slide PW Backup to 100% and set myself a reminder to adjust it back

 

[miimura]

I was wondering how to apply 10% guideline suggested by @BGbreeder too.

Regarding how to stop PW useage whike charging EV, I just slide PW Backup to 100% and set myself a reminder to adjust it back

If you are using Self Powered mode, I think the slider is your only option.

 

[Jeremy3292]

Yes, that price difference is what we’re talking about.
I use Time Based Control to prevent Powerwall usage while charging my car. The cars are both set to charge between midnight and 8am. The Powerwalls never discharge during that Off-Peak period. If I want to use surplus solar to charge the Tesla, I use the “Charge on Solar” feature. In order to ensure that it only uses Surplus Solar I only turn on the feature after the Powerwalls are above 95%. Then the car will soak up the afternoon solar until the rates go up. Then it will automatically stop.
If you want to charge a non-Tesla EV with surplus solar you have to use an EVSE that has that feature. Emporia is supposed to have it but I have not looked into the details. Zappi is famous for this feature outside North America.

Gotcha. So if I just set a crazy high on peak period (like $1 buy/$0 sell) and then a normal off peak period ($0.11 buy/$0.11 sell) it won’t use the powerwalls during off peak? I’ve seen a lot of threads on here where people have struggled with this so want to double check.

 

[miimura]

Gotcha. So if I just set a crazy high on peak period (like $1 buy/$0 sell) and then a normal off peak period ($0.11 buy/$0.11 sell) it won’t use the powerwalls during off peak? I’ve seen a lot of threads on here where people have struggled with this so want to double check.

I would start with your actual rates and see what it does. For the periods that are likely to have excess export, put the actual reimbursed rate of $0.04 instead of the zero you mentioned above. From what I’ve seen, you don’t have to put extreme numbers in to get the system to do what most people want.

 

[BGbreeder]

Buy/sell price 10% difference in the same TOU period? Meaning like buy $0.10 and sell $0.09 per kWh? Any advice on how to prevent powerwall usage when charging your car? Use grid/solar only.

If you have a Tesla, there is charge on solar. Personally, I just set a low(ish) charge rate and times when I know the solar is likely in excess. I don't micromanage it as we are generally net exporters. What I do focus on is trying to use power when we have solar. Dead of winter, the car charges at midnight for off peak, as the difference between on and off peak is too little to worry about. (i.e. close to 10% difference, so, here it is not worth trying to utilize Powerwalls, but I think that's highly dependent on your local rates, net export, and the energy balance during the day.

YMMV...

all the best,

BG

 

[Jeremy3292]

If you have a Tesla, there is charge on solar. Personally, I just set a low(ish) charge rate and times when I know the solar is likely in excess. I don't micromanage it as we are generally net exporters. What I do focus on is trying to use power when we have solar. Dead of winter, the car charges at midnight for off peak, as the difference between on and off peak is too little to worry about. (i.e. close to 10% difference, so, here it is not worth trying to utilize Powerwalls, but I think that's highly dependent on your local rates, net export, and the energy balance during the day.

YMMV...

all the best,

BG

I’m still awaiting my install from Tesla so trying to get good info beforehand. Based on PVwatts, in the spring/fall I’ll likely be a net exporter, in the summer I’ll likely be neutral/net zero, and in the winter I’ll definitely be pulling from the grid and be a net importer.

Yes, I have a Tesla and will use charge on solar during the day, but I usually charge after the sun goes down. This will likely be between 9pm-12am during off peak.

I feel as though my TOU periods with monthly netting complicates the situation, but perhaps I’m overthinking it. I listed the info and periods previously, but basically I need to avoid on peak with the powerwalls first and foremost. That seems pretty easy to do and setup in the app.

What I’m trying to figure out is how to set up my off peak rates, as that is going to be almost all of my solar production period. My buy and sell rate is effectively the same during this TOU period, until I become a net exporter during the month and then I only get $0.04 per kWh instead of the “buy” rate of $0.11 per kWh.

Basically anything over net zero for the month is $0.04 per kWh at any time of any day.