Powerwall 2: SGIP/Incentives

[miimura]

The spreadsheet you linked is not mine. Mine is here: PGE Electric Rate Calculator_v1.9.xlsx
This version has rates up through January 1, 2017.

I never went near the sub-meter pilot because I didn't want to pay for that electricity outside my true-up. Clearly sub-metering needs to be done, but I think the utilities are sandbagging because they don't really want to do it. A smart EVSE with sub-metering and demand response needs to be developed with all the standardized hooks so that they can be integrated into the utility systems. I have a feeling this will be a long and painful road. While they're at it, they should come up with a EV rate schedule specifically for those smart EVSE systems that include compensation for the demand response and also has the LCFS credits baked in.

As long as your PowerWalls can charge at least 75% from solar (in the first tax year), you should be eligible for the 30% Investment Tax Credit. Your ability to take advantage of the credit of course depends on the tax you owe. My solar is pretty small (4.32kW DC) so if I end up getting the 2 PowerWalls I've applied for, they will not be able to fill and discharge completely from solar in the Winter. That really doesn't concern me much because the grid is more stressed in the Summer and the rate arbitrage is greater then too.

Edit: I should also mention that all my historical Green Button data was wiped out by PG&E at my last true up. They changed my Electric Service ID and changed my account from 15 minute intervals to 1 hour intervals. I inquired multiple times with the Solar Customer Service department about recovering my interval data from my 2016 true-up and even escalated it as high as I could. The final conclusion is that the data is just gone. So, my advice to anyone who cares about that data - download it month by month because there is no guarantee that it will be available in the future.

 

[arnolddeleon]

The spreadsheet you linked is not mine. Mine is here: PGE Electric Rate Calculator_v1.9.xlsx
This version has rates up through January 1, 2017.

Even though PG&E wiped their version of my usage data I was able to transform the usage data from my power monitoring data to something similar. I tried using @miimura's spreadsheet but I got stumped at trying get the data to the Master Comparison table. I may also have not found all the places where the number of data rows in embedded. So I went a different route for now, I updated my version of the spreadsheet with latest rates:

PGE Billing Estimator 2017-05-29 with 2016-17 usage data

I was lazy and used @miimura summary of the rates. I'm assuming baseline quantities for "X" territory. I'm still showing that based on my usage last year E6 is better for me over EV-A. EV-A is better in the winter but loses in the summer. I have not done a double check yet for typos in the rates. If this is correct all you can see the big losing E-7 was to EV and PV drivers. That difference is will hopefully pay for the Powerwall 2s.

And since this is Powerwall 2 thread. Has anyone gotten any help from SolarCity/Tesla on the investment tax credit, particularly with adding storage to an existing solar system? They've been completely useless so far in that space. I get it, they don't give tax advice but good grief, can you at least tell me what if anything they are going to do with the needed (required?) documentation. I originally ignored the ITC since I didn't think it wouldn't work for me at all but now after some research it looks like it might. It might even justify the cost of a new panel if that is what allows Tesla to monitor solar production.

@superfly320 you said you are only getting backup power from the Powerwall 2. Did you apply for the SGIP rebate? The obligations require discharging at least equivalent of 52 full (rebated capacity) during peak hours as I understand it. Is that just not enabled yet?

arnold

 

[miimura]

The Master Comparison Table in my spreadsheet is not automatically populated. You have to copy the monthly calculated values on the Bill Calculation tab in the column starting from cell C66 and paste the values into the Comparison Table.

IIRC, @arnolddeleon is in Cupertino, so definitely in Baseline Territory X. The big difference between the rate plans is this;
E-7 collected a whole lot more solar generation in the Peak period without giving it away after the sun went down. This is because it was a simple Peak/Off-Peak schedule with Noon-6pm peak period M-F only.
E-6 only has Peak during the Summer and it is 1pm-7pm M-F, but also has Part-Peak. The tiers make this rate quite expensive if you go over 2X Baseline.
EV has 2pm-9pm Peak periods during the Summer and Winter and has 3-7pm Peak hours on weekends too. If you have a lot of Off-Peak EV charging or other Off-Peak usage, then the low priced and unlimited Off-Peak outweigh the higher Peak credits on E-6.

This is the best summary I've seen regarding the Battery Storage aspect of the 30% Investment Tax Credit:

“Currently, the investment tax credit provides a credit for storage only when the storage equipment is considered to be ‘electric generating equipment,’” explained Greg Jenner, a tax partner at business law firm Stoel Rives. “In other words, the credit for storage equipment ‘piggybacks’ on the credit for solar, instead of being freestanding. If the storage equipment can be charged from sources other than solar, it is considered ‘dual use equipment,’ which means that a portion of the ITC is disqualified to the extent of the charge derived from other sources (and completely denied if the charge exceeds 25%).”

Reference: Energy storage ITC may get a second chance

So, if the PowerWall is configured to charge exclusively from solar, you would be able to claim the full 30% ITC. If it charges only 90% from solar, then you could claim 90% of the 30%. If it charges less than 75% from solar, you can't get the ITC at all. The other thing that my tax accountant told me was that the 30% ITC is calculated after all other applicable rebates. I have seen it applied to the total installed cost even when SGIP was in play, which is wrong. I have not looked at the SGIP Manual to see what affect the ITC has on an SGIP application.

 

[superfly320]

Even though PG&E wiped their version of my usage data I was able to transform the usage data from my power monitoring data to something similar. I tried using @miimura's spreadsheet but I got stumped at trying get the data to the Master Comparison table. I may also have not found all the places where the number of data rows in embedded. So I went a different route for now, I updated my version of the spreadsheet with latest rates:

PGE Billing Estimator 2017-05-29 with 2016-17 usage data

I was lazy and used @miimura summary of the rates. I'm assuming baseline quantities for "X" territory. I'm still showing that based on my usage last year E6 is better for me over EV-A. EV-A is better in the winter but loses in the summer. I have not done a double check yet for typos in the rates. If this is correct all you can see the big losing E-7 was to EV and PV drivers. That difference is will hopefully pay for the Powerwall 2s.

And since this is Powerwall 2 thread. Has anyone gotten any help from SolarCity/Tesla on the investment tax credit, particularly with adding storage to an existing solar system? They've been completely useless so far in that space. I get it, they don't give tax advice but good grief, can you at least tell me what if anything they are going to do with the needed (required?) documentation. I originally ignored the ITC since I didn't think it wouldn't work for me at all but now after some research it looks like it might. It might even justify the cost of a new panel if that is what allows Tesla to monitor solar production.

@superfly320 you said you are only getting backup power from the Powerwall 2. Did you apply for the SGIP rebate? The obligations require discharging at least equivalent of 52 full (rebated capacity) during peak hours as I understand it. Is that just not enabled yet?

arnold

I did apply for the SGIP. I was curious about the discharge requirement as I am currently not capable of discharging the battery unless I kill the power to the house....which I am not planning on doing, at least frequently. The current word I got back from Tesla Concierge was that they will be enabling this feature "soon" via the Tesla App. So it is a waiting game now. I'm going to call them tomorrow to get an update on this.

For those of you with a Tesla, I was playing around with this and I set the car to charge at 30 amps and I flipped my main breaker to off to see if the PW would charge, and as you may have guessed, it did. (16 mi/hr).

 

[arnolddeleon]

Thanks @miimura again. I found error my spreadsheet, in the EV-A calculation I was referring to an empty cell for partial peak during the summer period. It became pretty obvious the error was going to be be there when I did side by side comparison with your spreadsheet. Now they give the same guidance, EV-A is much better than E-6.

arnold

 

[bonaire]

What's your arbitrage spread? (night kWh cost versus peak cost in mid-day/afternon) And will you be charging from the grid at night as well as from Solar PV? Given the Federal ITC is against dual-use, I suppose you must charge mostly from solar PV. SGIP doesn't seem to really care how batteries are charges - they want the battery power outputted during peak grid periods (later afternoon). But I would like to hear the engineering reason why they would suggest the 3rd powerwall. I would think it is due to demand load and not solar PV size.

 

[arnolddeleon]

What's your arbitrage spread? (night kWh cost versus peak cost in mid-day/afternon) And will you be charging from the grid at night as well as from Solar PV? Given the Federal ITC is against dual-use, I suppose you must charge mostly from solar PV. SGIP doesn't seem to really care how batteries are charges - they want the battery power outputted during peak grid periods (later afternoon). But I would like to hear the engineering reason why they would suggest the 3rd powerwall. I would think it is due to demand load and not solar PV size.

The spread $0.33/$0.195 summer/winter for EV-A (where I'm likely to go). With two Powerwalls it would be easy to charge them with solar with almost all off peak power. I'm trying to find out why the possible need for 3rd Powerwall but the impression I got was something akin to "overpowering" the batteries. This doesn't make sense to me since the Powerwalls presumably don't "blow up" when charging from the grid which can supply effectively infinite current. The Powerwalls already have to deal with signaling to the PV system when they're full. I'm assuming they were just going to dither the frequency.

arnold

 

[miimura]

3rd PowerWall doesn't make sense to me in your case. If the grid is down and the batteries are full, they should just move the frequency out of bounds so the solar will shut down. Easy. If the grid is up, the new batteries are AC coupled and if full when the solar is generating a lot, they just sit there.

 

[doubleohwhat]

It sounds like they've ran into some issues signaling the solar to shut down and are instead recommending a third powerwall to just soak up any solar produced.

 

[electracity]

3rd PowerWall doesn't make sense to me in your case. If the grid is down and the batteries are full, they should just move the frequency out of bounds so the solar will shut down. Easy. If the grid is up, the new batteries are AC coupled and if full when the solar is generating a lot, they just sit there.

THey may have determined that the charge rate is too high at peak solar. A customer isn't going to be happy dumping solar to the grid when the batteries are not near full.

Tesla is probably regularly tweaking the parameters the design engineers use, especially with a new product.

 

[bkp_duke]

What's your arbitrage spread? (night kWh cost versus peak cost in mid-day/afternon) And will you be charging from the grid at night as well as from Solar PV? Given the Federal ITC is against dual-use, I suppose you must charge mostly from solar PV. SGIP doesn't seem to really care how batteries are charges - they want the battery power outputted during peak grid periods (later afternoon). But I would like to hear the engineering reason why they would suggest the 3rd powerwall. I would think it is due to demand load and not solar PV size.

12 kW solar system, we'll be charging 100% from solar so that we can claim the ITC.

 

[miimura]

THey may have determined that the charge rate is too high at peak solar. A customer isn't going to be happy dumping solar to the grid when the batteries are not near full.

Tesla is probably regularly tweaking the parameters the design engineers use, especially with a new product.

If the grid is up, there is no problem. The batteries can charge at their normal rate and the grid will take the rest. However, if they cannot modulate the solar production and can only shut it down, then that would be a bad situation if the grid was down. The batteries could be low and the solar could be producing too much. In that case, they should work on better compatibility with SMA and others that do have the ability to modulate purely through AC waveform parameters.

However, that begs the question, @arnolddeleon how big is your solar system?

 

[bonaire]

It sounds like they've ran into some issues signaling the solar to shut down and are instead recommending a third powerwall to just soak up any solar produced.

The SolarEdge inverter is supposed to handle that. Or throw on a hot water heater or something similar as a typical demand element.

 

[idleuser]

Is solar city handling the SPIG rebates?

 

[arnolddeleon]

3rd PowerWall doesn't make sense to me in your case. If the grid is down and the batteries are full, they should just move the frequency out of bounds so the solar will shut down. Easy. If the grid is up, the new batteries are AC coupled and if full when the solar is generating a lot, they just sit there.

I agree. I'm guessing the concern is that the batteries are not full, the grid is down, there is enough sun so over 10 kW of power is available, and if the Powerwalls can't sink more than 10kW then what would happen? I would expect the simplest and most logical thing, the voltage should rise and eventually move out of spec and the PV system will stop producing.

I found a resource, DSIRE, that seems to suggest that SGIP is limited to 60% of the eligible cost and the ITC requires that applicant pay 40%. So unless you have an expensive install it would be hard for the ITC and SGIP to both kick in a big way. If this is correct then this reduces the difference between tier 1 and tier 2 rebates if you using Tesla for the install because their install costs are relatively low. The tier 2 rebate still almost hits the limit. For example, my proposed install is within less than 3% of the limit. Put another way, the ITC will at most gain me less than $500.

arnold

 

[arnolddeleon]

If the grid is up, there is no problem. The batteries can charge at their normal rate and the grid will take the rest. However, if they cannot modulate the solar production and can only shut it down, then that would be a bad situation if the grid was down. The batteries could be low and the solar could be producing too much. In that case, they should work on better compatibility with SMA and others that do have the ability to modulate purely through AC waveform parameters.

However, that begs the question, @arnolddeleon how big is your solar system?

10.9 kW + 2.54 kW STC rating. Of course in real life it is much smaller. The 10.9 kW system has 3 Outback GVFX3648 (3.6 kW peak) inverters. The 2.54 kW system has Xantrex inverter (I don't recall the model and specific rating). Looking at my data from last year, the theoretical "best production hour" was 10kWh so in practice this would never be an issue. And if for some reason we were having a super solar cold day and I didn't have any loads but I needed to charge the batteries and the system won't start because of too much power I would simply turn off one of the Outback inverters and voila the system cannot output more than 3.6 +3.6 +2.5 kW which is less than 10kW.

arnold

 

[miimura]

10.9 kW + 2.54 kW STC rating. Of course in real life it is much smaller. The 10.9 kW system has 3 Outback GVFX3648 (3.6 kW peak) inverters. The 2.54 kW system has Xantrex inverter (I don't recall the model and specific rating). Looking at my data from last year, the theoretical "best production hour" was 10kWh so in practice this would never be an issue. And if for some reason we were having a super solar cold day and I didn't have any loads but I needed to charge the batteries and the system won't start because of too much power I would simply turn off one of the Outback inverters and voila the system cannot output more than 3.6 +3.6 +2.5 kW which is less than 10kW.

arnold

Wait, What? Those are grid interactive battery inverters. So you already have some batteries? What solar charge controllers are you using? I'm confused about what you have and what you're trying to do.

 

[arnolddeleon]

Wait, What? Those are grid interactive battery inverters. So you already have some batteries? What solar charge controllers are you using? I'm confused about what you have and what you're trying to do.

Yes the Outback Inverters are grid interactive battery inverters but I'm not aware of any batteries that I can buy that will work with the system that makes power arbitrage work economically (nothing even close). I want to treat them as as plain old grid interactive PV system (ignore the batteries, they're just needed to make the system work). The controllers are MX60 and the modules are BP-585. It's 12+ year old system. Buying a battery based system 12+ years ago was a mistake. I'm going down the Powerwall 2 route now because it looks like with power arbitrage of solar and the SGIP I can make the system pay for itself in about 5-10 years and the backup system is "free".

BTW here is your PG&E rate spreadsheet with my data:
PGE Electric Rate Calculator_v1.9.xlsx

and the rate calculator I had with the bug fix and my data:
PGE Billing Estimator 2017-05-29 with 2016-17 usage data

They're close but not quite identical. I know one source of difference is the number of days assumed for minimum billing but I don't think accounts for all the difference. But given they're very similar I'm pretty confident of the results of the EV-A and E-6 at at this point.

 

[nativewolf]

Yes the Outback Inverters are grid interactive battery inverters but I'm not aware of any batteries that I can buy that will work with the system that makes power arbitrage work economically (nothing even close). I want to treat them as as plain old grid interactive PV system (ignore the batteries, they're just needed to make the system work). The controllers are MX60 and the modules are BP-585. It's 12+ year old system. Buying a battery based system 12+ years ago was a mistake. I'm going down the Powerwall 2 route now because it looks like with power arbitrage of solar and the SGIP I can make the system pay for itself in about 5-10 years and the backup system is "free".

BTW here is your PG&E rate spreadsheet with my data:
PGE Electric Rate Calculator_v1.9.xlsx

and the rate calculator I had with the bug fix and my data:
PGE Billing Estimator 2017-05-29 with 2016-17 usage data

They're close but not quite identical. I know one source of difference is the number of days assumed for minimum billing but I don't think accounts for all the difference. But given they're very similar I'm pretty confident of the results of the EV-A and E-6 at at this point.

Nice work!

 

[K-MTG]

Good answers, thanks. No, no Fed ITC for use as a backup battery. And you don't sound like you will use for energy arbitrage. It's a battery as a larger UPS for your home office and some additional circuits. I doubt you will be able to use it for 2-3 days. Consider getting a Ted 5000 or similar home energy monitor to determine your standard draw from the grid and you can deduce your backup runtime. UPS with Li-Ion batteries are growing and data centers are looking more and more at using Li-Ion over LA and other solutions for the instant failure-handling that occur when grid services go down.

Had you considered a UPS or using all laptops for home office usage? Family member of mine went from desktop to laptops to handle outage cut-overs in their home-business.

I ran my home business (few laptops and desktop, routers, cable modem) off my EV a year ago when the home's main circuit panel was replaced. Used about 7kWh from the battery through a 120V inverter drawing what appeared to be about 230W full-time for 6 hours. Losses through inversion a few times (from HV battery to DC-DC inverter to 12V and back up to 120V and so on) was enough to burn a lot of excess power. That was a constant draw of well under 1KW. Add in refrigerators and lighting and things add up quickly unless they are LED lighting and high-efficiency refrigerator (about 60-70W continuous when running, some start-up peak loads to get the compressor going).

I'd suggest you "try out an outage". One calm office day, shut off your main grid power. See how long run time is and figure out how you'll do in a grid failure. You may have already thought of this.

Perhaps you posted the previously, but what was your total cost before and after incentives?

Thanks