Powerwall Arbitrage DEAD: San Diego's SDGE

[wwhitney]

I'm in PG&E territory, but I had the same question, and here at least the answer is no. The interconnection request with the power company just has to be submitted properly. I ended up submitting my own interconnection request with PG&E, so I can't confirm whether or not Tesla is doing it properly, but hopefully they are.

Cheers, Wayne

 

[markb1]

I am in SDG&E territory and am also considering a PW to mitigate change in peak period hours on EV-TOU2. I am presently grandfathered in NEM 1.0. Installing Powerwalls doesn’t trigger a change that would bump me into NEM 2.0 would it?

I don't think it does, but if it did, is that a big deal? The big different with NEM 2.0 is the non-bypassable charges, which is a few cents per kWh on the NET amount of energy you export in a month (if I understand it correctly)

 

[wwhitney]

The big different with NEM 2.0 is the non-bypassable charges, which is a few cents per kWh on the NET amount of energy you export in a month (if I understand it correctly)

As I understand it, everyone pays the non-bypassable charges on the net amount of energy they use. For NEM 1.0, that net is calculated across an entire billing period. For NEM 2.0, it is calculated separately for each billing interval (I think 60 minutes for residential), with no credit for billing periods with net production.

So if I have that correct, then take a simple example where consumption is 20 kWh daily during nighttime hours, and production is 20 kWh daily during daytime hours. Under NEM 1.0, there would be no NBCs. Under NEM 2.0, there would be 20 kWh/day of NBCs.

Cheers, Wayne

 

[markb1]

As I understand it, everyone pays the non-bypassable charges on the net amount of energy they use. For NEM 1.0, that net is calculated across an entire billing period. For NEM 2.0, it is calculated separately for each billing interval (I think 60 minutes for residential), with no credit for billing periods with net production.

So if I have that correct, then take a simple example where consumption is 20 kWh daily during nighttime hours, and production is 20 kWh daily during daytime hours. Under NEM 1.0, there would be no NBCs. Under NEM 2.0, there would be 20 kWh/day of NBCs.

Cheers, Wayne

I'm not following. If your consumption equals your production in a monthly billing period*, your net is zero, so no NBCs, or at least that's the way I thought it worked.

*It's sloppy of them to say "billing period" when they mean monthly, because net metering customers are really billed annually, but that's another rant.

 

[FlatSix911]

There are hard-to-believe programs like this (sadly not in my locality though):
Retail Value for Surplus Generation
Rooftop Solar : Silicon Valley Clean Energy

I am enrolled in the SVCE NEM Program and dumped PG&E ... SVCE rocks

 

[wwhitney]

I'm not following. If your consumption equals your production in a monthly billing period*, your net is zero, so no NBCs, or at least that's the way I thought it worked.

That's the way it works with NEM 1.0, you look at each month's net consumption, and if it is zero or less (net production), no NBCs; if it is positive, you pay NBCs on the net consumption for that month. If you are a net producer during the month, you don't get any NBC credits to use against the NBCs in a month in which you are a net consumer; i.e. the NBCs are not net metered in that way.

With NEM 2.0, you instead look at each hour's net consumption. So for each hour in which you are net consumer, you pay NBCs on that hour's net consumption; for the hours in which you are a net producer, you pay no NBCs. Again, you also don't get a NBC credit for the hours in which you are a net producer.

At least, that is my understanding.

Cheers, Wayne

 

[markb1]

That's the way it works with NEM 1.0, you look at each month's net consumption, and if it is zero or less (net production), no NBCs; if it is positive, you pay NBCs on the net consumption for that month. If you are a net producer during the month, you don't get any NBC credits to use against the NBCs in a month in which you are a net consumer; i.e. the NBCs are not net metered in that way.

With NEM 2.0, you instead look at each hour's net consumption. So for each hour in which you are net consumer, you pay NBCs on that hour's net consumption; for the hours in which you are a net producer, you pay no NBCs. Again, you also don't get a NBC credit for the hours in which you are a net producer.

At least, that is my understanding.

Cheers, Wayne

For NEM 2.0, here's my source: http://regarchive.sdge.com/tm2/pdf/ELEC_ELEC-SCHEDS_NEM-ST.pdf

Nonbypassable charges will be calculated by multiplying the rate for each charge by the kWhs
consumed in each metered interval net of exports over the course of each monthly billing period.

I think "NET ENERGY METERING - SUCCESSOR TARIFF" is the official name of NEM 2.0.

I'm pretty sure there are no per-kWh NBCs in NEM 1.0. At least, I've never seen anything like that on my bill. There is a minimum monthly charge, though.

 

[wwhitney]

Right, it's the "in each metered interval" part that is new to NEM 2.0. The interval is (I believe) 60 minutes for residential (and I think 15 minutes for commercial). Delete the "in each metered interval" and you have NEM 1.0, which just looks at your net consumption over the entire billing period.

So if a billing period is 30 days and the interval is 60 minutes, you get 720 numbers for the billing period (the net consumption, positive or negative, for each interval). NEM 1.0 you add up all the numbers, and if the sum is positive multiply by the NBC rate. NEM 2.0 you add up just the positive numbers, ignoring the negative ones, and then multiply that partial sum by the NBC rate. That means NBCs are always higher in NEM 2.0.

Cheers, Wayne

 

[markb1]

Right, it's the "in each metered interval" part that is new to NEM 2.0. The interval is (I believe) 60 minutes for residential (and I think 15 minutes for commercial). Delete the "in each metered interval" and you have NEM 1.0, which just looks at your net consumption over the entire billing period.

So if a billing period is 30 days and the interval is 60 minutes, you get 720 numbers for the billing period (the net consumption, positive or negative, for each interval). NEM 1.0 you add up all the numbers, and if the sum is positive multiply by the NBC rate. NEM 2.0 you add up just the positive numbers, ignoring the negative ones, and then multiply that partial sum by the NBC rate. That means NBCs are always higher in NEM 2.0.

Cheers, Wayne

Ok, I will concede your point on NEM 2.0. I didn’t consider the meaning of “metering interval”, but it makes sense, now.

On NEM 1.0, where are you getting that there are NBCs?

 

[wwhitney]

On NEM 1.0, where are you getting that there are NBCs?

OK, I'm using the terminology loosely. If by NBCs we mean those charges that are netted out over each metering interval rather than netted out over the whole billing period, as far as I know in NEM 1.0 there are no NBCs. I was using the term NBC with respect to NEM 1.0 to refer to those components of the unbundled rates that have NBC status under NEM 2.0. In other words, as far as I know, the NBCs are not a new line item in the unbundled rates, just a new way of accounting for some of the existing unbundled components of the rates.

Cheers, Wayne

 

[wwhitney]

[NEM 1.0] If you are a net producer during the month, you don't get any NBC credits to use against the NBCs in a month in which you are a net consumer; i.e. the NBCs are not net metered in that way.

This part may be wrong; I don't know if any of the unbundled rate components are handled this way under NEM 1.0, or if they are all eligible for net metering on an annual basis.

Cheers, Wayne

 

[miimura]

I am enrolled in the SVCE NEM Program and dumped PG&E ... SVCE rocks

You are still paying PG&E delivery charges when using a CCA like SVCE. I am on SVCE Green Prime. Here's how the billing works:
1. Calculate PG&E Minimum Delivery Charge. Add to Amount Due.
2. Calculate PG&E charges on your chosen tariff, ie. EV-A, add to PG&E True-Up total
3. Calculate Generation portion from unbundled rates on that tariff. Subtract from PG&E True-Up total.
4. Calculate Power Charge Indifference Adjustment. Add to PG&E True-Up total.
5. Calculate SVCE Generation from their tariff. If a positive balance is owed, add to Amount Due. If credit balance, carry forward to SVCE true up.

The main benefit is for people who have dollar credit balances at the end of the year. SVCE will pay out all generation credits while PG&E will wipe out your credit balance. PG&E only pays for surplus kWh generation at ~3.5c/kWh. PG&E will still wipe out negative balances from distribution charges at true-up.

 

[FlatSix911]

The main benefit is for people who have dollar credit balances at the end of the year. SVCE will pay out all generation credits while PG&E will wipe out your credit balance. PG&E only pays for surplus kWh generation at ~3.5c/kWh. PG&E will still wipe out negative balances from distribution charges at true-up.

Thank you for reinforcing my point ... SVCE will also pay out credits at the full retail rate vs. wholesale with PG&E

 

[jtinla]

You need to check the interconnect agreement with the utility. I believe PG&E currently prohibits discharging batteries into the grid. So, the best arbitrage you can do during the Peak period is to satisfy your internal loads with the battery and let the solar feed into the grid. Also, if you take the SGIP incentive or the ITC tax credit you have to charge the batteries from solar, so the best you can do is charge up the batteries in the morning, hopefully before the Peak period starts, then ride it through the Peak period on batteries.

Finally, someone has stated it correctly. There is no arbitrage with PW2 because: 1) the PW2 does not have the software capable of determining when is the best time to discharge to the grid and 2) because the utility will not allow the PW2 to discharge to the grid because it can be charged from either solar or the grid; if a battery is capable of being charged from the grid, then it cannot discharge to the grid. The PW2 is strictly for backup power of "critical loads" (i.e. those circuits wired into a subpanel determined by homeowner to be necessary during a grid outage) and self-consumption. Obviosuly, the loads you plan to backup will determine how long you can run a PW2, and almost guaranteed you will not be running you A/C on backup. Even the "whole home backup" option from Tesla (which is two PW2s) won't likely do the trick. However, the PW2 can TOU shift, which simply means the homeowner can store PV-generated kWh in the PW2 during daytime hours and they can draw that power from the PW2 at night when power is more expensive (under NEM 2.0 and upcoming mandatory TOU tariffs with late afternoon/evening peak periods). By the way, those of you who think you are grandfathered at your current rates or peak periods because you're part of NEM 1.0, this is not the case. You are grandfathered at those rates/periods for only 5 years from PTO or 2022, whichever is later. There are other products on the market that allow true arbitrage (i.e. export to the grid), but PW2 is not one of them currently.

 

[miimura]

Finally, someone has stated it correctly. There is no arbitrage with PW2 because: 1) the PW2 does not have the software capable of determining when is the best time to discharge to the grid and 2) because the utility will not allow the PW2 to discharge to the grid because it can be charged from either solar or the grid; if a battery is capable of being charged from the grid, then it cannot discharge to the grid. The PW2 is strictly for backup power of "critical loads" (i.e. those circuits wired into a subpanel determined by homeowner to be necessary during a grid outage) and self-consumption. Obviosuly, the loads you plan to backup will determine how long you can run a PW2, and almost guaranteed you will not be running you A/C on backup. Even the "whole home backup" option from Tesla (which is two PW2s) won't likely do the trick. However, the PW2 can TOU shift, which simply means the homeowner can store PV-generated kWh in the PW2 during daytime hours and they can draw that power from the PW2 at night when power is more expensive (under NEM 2.0 and upcoming mandatory TOU tariffs with late afternoon/evening peak periods). By the way, those of you who think you are grandfathered at your current rates or peak periods because you're part of NEM 1.0, this is not the case. You are grandfathered at those rates/periods for only 5 years from PTO or 2022, whichever is later. There are other products on the market that allow true arbitrage (i.e. export to the grid), but PW2 is not one of them currently.

One clarification. You likely cannot run your A/C from the PowerWall during a grid outage unless it is small and has a soft start. However, you can use the PowerWall to offset its energy use while the grid is up, even if it is on a panel that is not backed up. The PowerWall should be measuring the total usage just inside the utility meter and offset the usage the best it can.

 

[miimura]

Thank you for reinforcing my point ... SVCE will also pay out credits at the full retail rate vs. wholesale with PG&E
View attachment 275838

Just to be absolutely clear, SVCE "retail value for surplus generation" is not the same as the PG&E retail tariff. SVCE rates on EV are as follows:

The PG&E retail tariff is roughly double that. Sure, SVCE reimbursement is better than the 3.5c/kWh from PG&E Net Surplus Compensation, but it's not the full TOU credit balance that you would see on your PG&E true-up.

 

[suwaneedad]

Finally, someone has stated it correctly. There is no arbitrage with PW2 because: 1) the PW2 does not have the software capable of determining when is the best time to discharge to the grid and 2) because the utility will not allow the PW2 to discharge to the grid because it can be charged from either solar or the grid; if a battery is capable of being charged from the grid, then it cannot discharge to the grid. The PW2 is strictly for backup power of "critical loads" (i.e. those circuits wired into a subpanel determined by homeowner to be necessary during a grid outage) and self-consumption. Obviosuly, the loads you plan to backup will determine how long you can run a PW2, and almost guaranteed you will not be running you A/C on backup. Even the "whole home backup" option from Tesla (which is two PW2s) won't likely do the trick. However, the PW2 can TOU shift, which simply means the homeowner can store PV-generated kWh in the PW2 during daytime hours and they can draw that power from the PW2 at night when power is more expensive (under NEM 2.0 and upcoming mandatory TOU tariffs with late afternoon/evening peak periods). By the way, those of you who think you are grandfathered at your current rates or peak periods because you're part of NEM 1.0, this is not the case. You are grandfathered at those rates/periods for only 5 years from PTO or 2022, whichever is later. There are other products on the market that allow true arbitrage (i.e. export to the grid), but PW2 is not one of them currently.

Fascinating read, this entire thread, from an Atlantan back East. I've never considered that I could make a solar and PW investment and then have the local utility come along and change the rules on the fly (TOU, and the various games embedded within the various tariffs). The entire concept of the utility NOT rewarding at retail for energy pushed back onto the grid, regardless of whether that energy was sourced off-peak or from solar, is Exhibit A of just how self-interested the utilities and their respective public utility commissions have become.

For example, in Georgia the rate payers footed the bill to construct a hydro power plant that pushes water uphill into a reservoir overnight at cheap pricing, and then lets that water flow through the hydro generators during afternoon peak into the reservoir below. Lather/Rinse/Repeat daily. To think that the very same utility and PUC will not pay residential customers to engage in the very same activity on a micro level is ridiculous. I used to audit the local power company; ostensibly a huge part of their mission is to engage in various capacity reduction initiatives to dampen necessary capital investment in the system, just as they create TOU plans to load-level. I suspect that these bad actors at the power companies and PUCs will ultimately be penalized: my aim is to simply get off the grid by using sufficient Tesla Solar Roof + PW2 capacity to render the local utility irrelevant to my life. Cut the cord, 21st century-style!

 

[FlatSix911]

Just to be absolutely clear, SVCE "retail value for surplus generation" is not the same as the PG&E retail tariff. SVCE rates on EV are as follows:

View attachment 276031

The PG&E retail tariff is roughly double that. Sure, SVCE reimbursement is better than the 3.5c/kWh from PG&E Net Surplus Compensation, but it's not the full TOU credit balance that you would see on your PG&E true-up.

Thanks for the clarification ... I'll take 19.8c/kWh peak any day compared to the reimbursement of 3.5c/kWh from PG&E
BTW, we live in the same village ... what size is your PV system?

 

[miimura]

Thanks for the clarification ... I'll take 19.8c/kWh peak any day compared to the reimbursement of 3.5c/kWh from PG&E
BTW, we live in the same village ... what size is your PV system?

Too small. 4.32kW DC on Enphase micro inverters. It's only enough to offset the house, not the two EVs. Two PowerWalls going in next week, allegedly.

 

[FlatSix911]

Too small. 4.32kW DC on Enphase micro inverters. It's only enough to offset the house, not the two EVs.
Two PowerWalls going in next week, allegedly.

Let us know how the PW installation goes and post some photos