Powerwall 2: TOU/Rate Arbitrage

[David L]

The financial case for the Powerwall 2 may get a bit stronger after SDG&E changes their TOU rate peak time to 3 to 9PM sometime in 2018, in which case the battery can offset peak usage from sunset to 9PM. Time-of-Use Period Grandfathering for Net Energy Metering Customers | San Diego Gas & Electric

By the way, can people from San Diego recommend solar and/or Powerwall 2 installers (besides SolarCity)? I'm planning to get solar and possibly a Powerwall 2 installed. Any idea if Tesla is prioritizing Powerwall 2 deliveries through SolarCity vs. 3rd party installers?

 

[miimura]

PG&E EV rate already goes to 9pm and has since inception. This schedule was initiated with the predecessor E-9 Experimental EV rate.

 

[Brovane]

I was looking at the SGIP weekly statewide Report this morning and running some numbers in Excel

Pacific Gas and Electric - Small Residential Step 1 - Total is 423 SGIP Applications and 133 RRF Confirmed so 31% of Step 1 Small Residential SGIP applications have been RRF confirmed.

SCE - Small Residential Step 1 - Total is 329 SGIP Applications and 0 RRF confirmed. So in over 2-months SCE has been able to confirm Zero SGIP applications. Great Job as usual SCE.

 

[bkp_duke]

Yep, that sounds like SCE.

I'm leaning towards keeping my two PW's just to stick it to SCE when they change TOU times to evening. Pump back into the grid at max profit time so they can kiss my A$$.

 

[Merrill]

Yes as soon as Pacific Graft and Extortion takes away net metering, which they are trying to do then I get a powerwall. They say in their marketing that they want you to save money with efficient mechanicals and they are all over solar, but their actions are the opposite.

 

[electracity]

Yes as soon as Pacific Graft and Extortion takes away net metering, which they are trying to do then I get a powerwall. They say in their marketing that they want you to save money with efficient mechanicals and they are all over solar, but their actions are the opposite.

Is PG&E taking away net metering for existing solar owners? I thought is was grandfathered long enough to roughly pay off existing systems.

 

[SoundDaTrumpet]

PG&E grandfathering of net metering only partially protects solar owners interests, and is not comprehensive enough. PG&E can "at will" change the rate schedules, especially peak pricing hours. I bought into solar during the time when E-1, E-6, and EV-A/B was available and wondered why at the time installers didn't factor in time-of-use (TOU) rate schedule when sizing systems. Now I know why. The installers didn't want to be liable for rate schedule changes in the future. Yes it was a smart move on their part as peak to non-peak rates for the current available E-TOU (for non-EV owners) only carry a 10-30%, which isn't great for solar. To worsen the benefits to solar, future E-TOU peak will shift to 4-9PM as stated in the rate schedule. In essence, E-TOU is practically "flat rate" rate schedule during optimal solar production effectively eliminating rate arbitrage. Although net metering isn't going away for ~20 years, PG&E is indirectly taking it away by chipping away at solar benefits. I am not at all trying to bad mouth PG&E. On contrary, I am 100% on-board with their attempt to level-out demand of grid users. The installation of a powerwall will be grid friendly and well worth the wait.

I am on the EV rate schedule which is leaps and bounds the best rate schedule. I suspect the only reason it exists is that PG&E simply don't want us charging the cars immediately after our commutes, and wish to collect some revenue while their 24/7 natural gas base power stations operate throughout the night.

 

[Merrill]

Is PG&E taking away net metering for existing solar owners? I thought is was grandfathered long enough to roughly pay off existing systems.

No, I'm grandfathered in til 2020. But I think they will figure away to somehow collect more money.

 

[miimura]

Is PG&E taking away net metering for existing solar owners? I thought is was grandfathered long enough to roughly pay off existing systems.

PG&E Net Metering may be going away in less than 20 years, but any customer who is currently interconnected under the NEM Tariff or the NEM2 Tariff is guaranteed 20 annual true-ups from their original utility interconnection Permission to Operate (PTO) under their original Net Metering Tariff. For example, a new solar system in 2022 may not get full Net Metering treatment and instead follow whatever scheme is available at that time, but I will be allowed to continue on the NEM Tariff until December 2032 because I received my PTO in December 2012. This treatment is transferrable to subsequent customers (either property renters or purchasers) for the full original term. This is all spelled out in the Tariff documents available here.

 

[Skotty]

 

[electracity]

Will Tesla provide sophisticated management? Like "charge my car with solar before my powerwall"?

 

[miimura]

Will Tesla provide sophisticated management? Like "charge my car with solar before my powerwall"?

I think that case is already covered by "charge Powerwall with surplus solar only". The more magical thing would be "charge my car with surplus solar after the PowerWall is above X%".

 

[ohmman]

I think that case is already covered by "charge Powerwall with surplus solar only". The more magical thing would be "charge my car with surplus solar after the PowerWall is above X%".

They are promising a TOU setting on the app "soon." I think this will allow for much more granular control. I'd love to use my PWs to supply my late peak power (sundown-9pm). I bought them for backup purposes, but that would be a decent economic bonus.

 

[Dave EV]

They are promising a TOU setting on the app "soon." I think this will allow for much more granular control. I'd love to use my PWs to supply my late peak power (sundown-9pm). I bought them for backup purposes, but that would be a decent economic bonus.

That would also be good for the grid and reduce CO2 emissions as well by taking load off of inefficient peaker plants.

 

[jeffy1021]

Looks like the NBCs for PG&E are a tad higher. The total is $0.02329/kWh and is based on interval data.

• Public Purpose Programs (all usage) $0.01501
• Nuclear Decommissioning (all usage) $0.00149
• Competition Transition Charges (all usage) $0.00130
• DWR Bond (all usage) $0.00549

This is taken from the PG&E's EV Tariff. The NEM2 tariff reference CPUC Decision D.16-01-044 and CPUC Resolution E-4792 regarding the calculation of NBCs.

Figured it out. According to this page: Net Energy Metering Program | San Diego Gas & Electric
NBCs are made up of the following (with the apparent rates at the end of each):

• Public Purpose Programs (PPP) charge - $0.01063
• Nuclear Decommissioning (ND) charge - $-0.00049
• Competition Transition Charge (CTC) - $0.00177
• Department of Water Resources Bond Charge (DWR-BC) - $0.00549

Add it all up and you get $0.0174 / kWh.

 

[insaneoctane]

I have a question that I'm not googling to an answer about the PW2.....

I've got 6kW solar today on TOU at SCE in Southern California with net metering. I currently am a NET CONSUMER off the grid, but with TOU I'm able to time-shift my usage in a very advantageous manner such that at the end of my 12 month true-up period, I've got about a $500 credit on my bill. SCE then wipes the slate clean, sends me a check for pennies on the dollar (like I get a check for $50 vs the $500 credit) and we rinse and repeat. Fast forward a few months when my Model 3 starts to consume lots of kWh. My estimates show that my EV usage will completely wipe out the $500 credit and probably cost me about $500 per year in night time, low cost, consumption.

Now, for my question. This is not your typical green save-the-world question. If I get a PW2, can I time-shift it's function to continue to leverage the TOU that I'm currently benefiting from? Meaning I would want to ONLY use the PW2 to fill up at night and discharge during the day to produce enough credit to fully offset my expected EV usage (again, that's approximately 3kWh/year). If a single PW2 has additional capacity beyond what I need it for, I could use that to do more of what I think it's intended for which is to offset my pull from the grid. Of course, I'd also like the option of being able to disconnect from the grid if I want, too. And lastly, and maybe most important, I would only be able to consider the PW2 options if I got all these rebates SGIP, etc. Would my usage qualify for SGIP? Can I operate my way some percentage, then a required way another percentage and still qualify? Any guidance appreciated!

 

[abasile]

If I get a PW2, can I time-shift it's function to continue to leverage the TOU that I'm currently benefiting from? Meaning I would want to ONLY use the PW2 to fill up at night and discharge during the day to produce enough credit to fully offset my expected EV usage (again, that's approximately 3kWh/year).

I'm also an SCE customer who appreciates the benefits of NEM (net energy metering) and TOU, and I had the same question when I first started investigating the Powerwall 2.

There's no ability, with the current and expected PW2 software, to supply power to the grid from the battery. The utility companies don't yet have a rate structure for this. The reason for NEM, at this stage, is to incentivize the generation of renewable energy, not to incentivize arbitrage on grid-sourced energy.

That said, I think there's plenty of value in the Powerwall as a backup solution, even if it won't come close to paying for itself by reducing on-peak electricity usage.

 

[insaneoctane]

I'm also an SCE customer who appreciates the benefits of NEM (net energy metering) and TOU, and I had the same question when I first started investigating the Powerwall 2.

There's no ability, with the current and expected PW2 software, to supply power to the grid from the battery. The utility companies don't yet have a rate structure for this. The reason for NEM, at this stage, is to incentivize the generation of renewable energy, not to incentivize arbitrage on grid-sourced energy.

That said, I think there's plenty of value in the Powerwall as a backup solution, even if it won't come close to paying for itself by reducing on-peak electricity usage.

Thanks for the reply. I don't think that I want to supply power to the grid (maybe I mis-stated, or did not think through it well?) What about ensuring that my peak time consumption is always from battery vs grid? It gets sticky because I do have peak time consumption, but it is generally less than my PV generation. I think my TOU runs the peak rate all the way until 8pm, which means that for a few hours (more in the winter than summer for sure) I don't have much if any PV and would like to use battery....I do have the rub that says if I have over production during the expensive TOU period, I *do* want to send that to the grid because I profit from the TOU leverage. Can I change the PW2 at night? Maybe the PW2 isn't for me, but I thought that there might be some folks in a similar situation to me that have already figured this stuff out. I have too many questions and not a lot of answers!
I'm just trying to use the rebate opportunity to get an amazing deal on a PW2 if I can....If I can get short ROI and make the world a little greener. Don't want to look back in a few months or years and say "Now why the hell didn't I jump on that?"

 

[miimura]

The Powerwall will naturally eliminate your Peak period usage from the grid. That is automatic. However, it's not the same as pushing ALL your solar to the grid because the battery will let the solar power your household loads before it drives the grid usage to zero. Only when the battery is completely full and the solar is still generating will you earn Peak period credits. This is one reason that I want to have TOU settings in the Powerwall so that there will be no discharge from the batteries during my PG&E Off-Peak 11pm-7am period. Eliminating that discharge in self-powered mode will allow the batteries to be filled earlier in the day so that I can earn more Peak period credits.

Taking this one step further, you may want to charge the Powerwall from the grid during the Off-Peak period. If you change it to Backup Mode with 100% reserve, it will charge. However, you would need some kind of scripting system to do that automatically for you since it's not a configurable feature and you won't want to do it manually every night at 11pm and set it back at 7am.

 

[shokunin]

However, it's not the same as pushing ALL your solar to the grid because the battery will let the solar power your household loads before it drives the grid usage to zero. Only when the battery is completely full and the solar is still generating will you earn Peak period credits.

Is there a way for all solar to go the grid and power the home from the powerwall first? Is the position of the breakers or something else that determines which powers what first.

In other words, if I wanted all power to source from the Powerwalls first, then self generating solar, then grid if needed would that ever be possible?