Dumping Excess Power During Peak Period

[MichaelCo]

Just had the PW2 installation completed on Tuesday, and have it configured for "Cost Saving". I had been told I would be able to dump PW excess power to the grid during peak periods, by setting the "Reserve for Power Outages", and the "Price Schedule" (Off Peak, Shoulder and Peak). The PWs will fully charge by the start of the peak period, and I'd like to have it dump power to the grid until the it hit the "Reserve for Power Outages" set point.

The best I can achieve is to have house load sourced by the PWs during Peak Period, but, it's limited to the house draw, and none of the PW power will go to the grid. I am in PG&E territory - Is the PW unable to do this, or, is there a way to accomplish?

 

[Sonus]

You can't dump PW power the grid (at least not yet), you can use its power to power your home and if you have solar, the solar, during that time, will go to the grid. if you don't have solar you can't send power to the grid at all.

 

[miimura]

I had this misunderstanding before I had Powerwalls installed too. I assumed that I would be able to fully discharge the Powerwall each day regardless of my actual consumption. It is not true.

Actually, if you have solar and you read the tariff, you will see that PG&E specifically disallows credit for any energy exported that is in excess of your solar production. So, the best you can do is to power your house from the Powerwall batteries and let all your solar go to the grid during Peak hours. This is what Time Based Control will do. When you get the Powerwall billing from PG&E you will see that there is a column in the report called "Solar Generation Eligible for Credit". This was implemented in the NEM Paired Storage billing system in 2019.

 

[power.saver]

The CPUC ruled on this last year.

CPUC Decision here

It is now permissible to do this in California. However, PWs do not (yet) have a configuration setting that allows it to happen.

 

[miimura]

It is now permissible to do this in California. However, PWs do not (yet) have a configuration setting that allows it to happen.

IIRC, the decision allows you to export from batteries to the grid, but only if charged from on-site generation. No grid charge from Off-Peak and discharge into Peak is allowed. Am I remembering that right?

 

[power.saver]

Correct. You can either have "No Grid Export" (e.g. Grid Charging) or "No Grid Charging" (e.g. Export allowed). But any export must come from on-site generation. The idea is you can load up the batteries in the morning and then export that energy later in the peak, to help reduce grid demand.

 

[MichaelCo]

I had this misunderstanding before I had Powerwalls installed too. I assumed that I would be able to fully discharge the Powerwall each day regardless of my actual consumption. It is not true.

Actually, if you have solar and you read the tariff, you will see that PG&E specifically disallows credit for any energy exported that is in excess of your solar production. So, the best you can do is to power your house from the Powerwall batteries and let all your solar go to the grid during Peak hours. This is what Time Based Control will do. When you get the Powerwall billing from PG&E you will see that there is a column in the report called "Solar Generation Eligible for Credit". This was implemented in the NEM Paired Storage billing system in 2019.

Thanks for your response. We produce excess power in the range of 30-50 KWh in a given day - I would like to send most of this excess to the grid and choose the timing when the grid has it's highest demand - irregardless to whether it was produced during the off peak period. Seemed like this would be desirable for all, even for the utility (to some degree) - It could be viewed as all of the PW installations as an extension of entire power infrastructure. When utilities invest in energy storage they "even out" the loading and often "bank" energy produced during off peak times which is distributed during peak period.

Sounds like the rules for credit require the power sent to the grid to have been created at the moment, and not created some time earlier (off peak).

 

[MichaelCo]

It is now permissible to do this in California. However, PWs do not (yet) have a configuration setting that allows it to happen.

Thanks, good to hear - do you have a link to this change, or words to do a Google search?

 

[jjrandorin]

Thanks for your response. We produce excess power in the range of 30-50 KWh in a given day - I would like to send most of this excess to the grid and choose the timing when the grid has it's highest demand - irregardless to whether it was produced during the off peak period. Seemed like this would be desirable for all, even for the utility (to some degree) - It could be viewed as all of the PW installations as an extension of entire power infrastructure. When utilities invest in energy storage they "even out" the loading and often "bank" energy produced during off peak times which is distributed during peak period.

Sounds like the rules for credit require the power sent to the grid to have been created at the moment, and not created some time earlier (off peak).

They dont want people setting up to be mini utilities, is what it seems like to me, which seems extremely reasonable. "Residential" should mean that you are offsetting your own power usage, either by creating solar and pulling it back later (net metering) or using it via batteries.

It makes zero financial sense for any utility to allow a person to charge their powerwalls off peak, then discharge during peak. It does make financial sense to allow you to use power from your powerwalls during peak time, and send any power you are generating at that moment to the grid because you dont need it.

People want to, in effect, say ""I want to buy that cookie from you at midnight for 12 cents, and then I want to sell it back to you tomorrow at 4pm for 45 cents... sounds like a good deal to me. You just turn around and sell that cookie for 45 cents to someone else once I sell it back to you"

I cant imagine how that would ever work at any sort of scale.

 

[power.saver]

Sounds like the rules for credit require the power sent to the grid to have been created at the moment, and not created some time earlier (off peak).

No. The new Decision allows for on-site generation to be stored in batteries and returned to the grid at a later time.

Thanks, good to hear - do you have a link to this change, or words to do a Google search?

The Decision can be found here. Additional information from CALSSA can be found here.

They dont want people setting up to be mini utilities, is what it seems like to me, which seems extremely reasonable. "Residential" should mean that you are offsetting your own power usage, either by creating solar and pulling it back later (net metering) or using it via batteries.

It makes zero financial sense for any utility to allow a person to charge their powerwalls off peak, then discharge during peak. It does make financial sense to allow you to use power from your powerwalls during peak time, and send any power you are generating at that moment to the grid because you dont need it.

People want to, in effect, say ""I want to buy that cookie from you at midnight for 12 cents, and then I want to sell it back to you tomorrow at 4pm for 45 cents... sounds like a good deal to me. You just turn around and sell that cookie for 45 cents to someone else once I sell it back to you"

I cant imagine how that would ever work at any sort of scale.

The CPUC did this to allow you to shift your on-site generation to a time that's more beneficial to the grid. But they included restrictions that prevent you from charging batteries from the grid at one rate and discharging at another rate. You must agree to either "no grid charging" or "no storage export". For PW with solar, the practical use case is "no grid charging" so that you can do storage export.

 

[aesculus]

It is now permissible to do this in California. However, PWs do not (yet) have a configuration setting that allows it to happen.

Let me ask the hypothetical:

Lets say I generate 25 kWh or solar a day but only consume 5 kWh of energy during the "peak" period. For me that would be 3pm to 9PM M-F.

Would the new rule, if implemented in the PW, allow me to export the remaining 20 KWh of generated power back to the utility during peak period and then consume from them during partial and off peak? ie not WHEN I generate the extra power which is how it works now, but at the time I get the most value from it cost wise.

Of course my PWs would have to have the capacity to play that game but just wondering.

 

[MichaelCo]

It makes zero financial sense for any utility to allow a person to charge their powerwalls off peak, then discharge during peak.
.

There is value to the utility to have PWs storing energy and releasing during high demand periods. Whether it makes financial sense at the ~$.45 rate is another matter. But, there is value (to some degree), and should be compensated at some premium. One could question whether it makes sense for the utility to pay the off peak price when buying back power, as this is well above the wholesale price. At some point, when the ratio of solar installations to non solar tilts too far this may need to be revisited.

 

[aesculus]

BTW a bit off topic but this is about the first week we have had constant sun. I also lowered my reserve from 60% to 50%. And most importantly we have not needed much electrical heating during peak so our consumption has gone down dramatically.

I noticed today that my PWs have been sending power to the utility even though the PWs are only 75% charged during partial peak. Up until today they would first charge to 100% and then send the extra solar to the grid, or when we hit peak, all solar to the grid and drain the pws.

I was alarmed and called Tesla support and they told me that is the way cost savings mode works. It runs a rolling week load analysis and figures out how much power it thinks it needs for peak consumption plus your stated reserve and that is the SoC it uses to determine when to send power to the grid.

So in my case it thinks I won't use more than 25% during peak plus my 50% reserve. So 75% is my new max SoC.

 

[power.saver]

Let me ask the hypothetical:

Lets say I generate 25 kWh or solar a day but only consume 5 kWh of energy during the "peak" period. For me that would be 3pm to 9PM M-F.

Would the new rule, if implemented in the PW, allow me to export the remaining 20 KWh of generated power back to the utility during peak period and then consume from them during partial and off peak? ie not WHEN I generate the extra power which is how it works now, but at the time I get the most value from it cost wise.

Of course my PWs would have to have the capacity to play that game but just wondering.

Yes, that is correct. The idea is to use batteries as distributed storage, so solar generation during the solar peak, which is when there is too much generation already, can be put back into the grid later during the time when generation costs are high.

 

[MichaelCo]

No. The new Decision allows for on-site generation to be stored in batteries and returned to the grid at a later time.



The Decision can be found here. Additional information from CALSSA can be found here.



The CPUC did this to allow you to shift your on-site generation to a time that's more beneficial to the grid. But they included restrictions that prevent you from charging batteries from the grid at one rate and discharging at another rate. You must agree to either "no grid charging" or "no storage export". For PW with solar, the practical use case is "no grid charging" so that you can do storage export.

They dont want people setting up to be mini utilities, is what it seems like to me, which seems extremely reasonable. "Residential" should mean that you are offsetting your own power usage, either by creating solar and pulling it back later (net metering) or using it via batteries.

It makes zero financial sense for any utility to allow a person to charge their powerwalls off peak, then discharge during peak. It does make financial sense to allow you to use power from your powerwalls during peak time, and send any power you are generating at that moment to the grid because you dont need it.

People want to, in effect, say ""I want to buy that cookie from you at midnight for 12 cents, and then I want to sell it back to you tomorrow at 4pm for 45 cents... sounds like a good deal to me. You just turn around and sell that cookie for 45 cents to someone else once I sell it back to you"

I cant imagine how that would ever work at any sort of scale.

here

Thank you for the link and information.

 

[Skryll]

You can't dump PW power the grid (at least not yet), you can use its power to power your home and if you have solar, the solar, during that time, will go to the grid. if you don't have solar you can't send power to the grid at all.

But it doesn't even do that fully. I have had it charged to 90% and the only thing it does right at peak is to stop charging the battery and start using solar to power the home and feed the leftovers to the grid.

Sometimes for a short period of time, i.e. at low incoming solar after 5pm, it would do what I would love it to do all the time during peak, which is power home from battery and direct all solar to grid. But most of the time it doesn't, even with the battery charged to 90%.

I have 3 home batteries close to 40kWh capacity, 10kW solar panels (40x250W) via two SMA sunny boy inverters.

 

[power.saver]

But it doesn't even do that fully. I have had it charged to 90% and the only thing it does right at peak is to stop charging the battery and start using solar to power the home and feed the leftovers to the grid.

Sometimes for a short period of time, i.e. at low incoming solar after 5pm, it would do what I would love it to do all the time during peak, which is power home from battery and direct all solar to grid. But most of the time it doesn't, even with the battery charged to 90%.

I have 3 home batteries close to 40kWh capacity, 10kW solar panels (40x250W) via two SMA sunny boy inverters.

What is your configuration setting? Are you using TBC Cost Savings? That's what I use, and it does what you want (powers the house from battery and all solar goes to the grid during the Peak period).

 

[Sonus]

But it doesn't even do that fully. I have had it charged to 90% and the only thing it does right at peak is to stop charging the battery and start using solar to power the home and feed the leftovers to the grid.

Sometimes for a short period of time, i.e. at low incoming solar after 5pm, it would do what I would love it to do all the time during peak, which is power home from battery and direct all solar to grid. But most of the time it doesn't, even with the battery charged to 90%.

I have 3 home batteries close to 40kWh capacity, 10kW solar panels (40x250W) via two SMA sunny boy inverters.

Are you sure you are on cost savings? and the peak times are set correctly? what you are describing is not what is shod do in cost-savings mode.

 

[Skryll]

What is your configuration setting? Are you using TBC Cost Savings? That's what I use, and it does what you want (powers the house from battery and all solar goes to the grid during the Peak period).

In advanced / cost savings mode I use the PG&E EV-A time settings (off-peak, mid-peak and on-peak times). It does charge the battery at mid-peak which makes sense since that starts at 7am, and solar kicks in shortly after that. It does stop charging the battery at peak which makes sense. However it is NOT using the battery to offset all home use in peak, even when very highly charged. I have it set with 20% backup capacity and it may still have 70% left after peak time is over.

Because of that I sometimes switch by hand to fully self powered so that it covers all of home use with the battery and then just before peak starts, switch to advanced so that it can do its thing until peak is over, then switch back to self powered for the night.

This of course works mostly so well because I am not changing my cars at night since we don't commute during shelter in place due to covid19. I envision that in the future it would be staying on advanced mode over night and charge the car off the grid in the off-peak time window.

Example:

Note how 3pm to 4pm it did the right thing, using the battery. Then despite still being at say 80% or so, it stopped using it and so despite having enough energy to donate all solar to grid, it just doesn't as the home use went high from AC and cooking.

 

[power.saver]

Probably the manual switching between self powered and TBC isn't helping. I don't do any switching and it works fine.