TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC
Start a Discussionhttps://teslamotorsclub.com/tmc/tags/

Powerwall 2, Swell and SDG&E does this make sense?

Discussion in 'Tesla Energy' started by Princeb, Oct 7, 2017.

  1. Princeb

    Princeb Member

    Joined:
    Oct 7, 2017
    Messages:
    7
    Location:
    San diego
    Hi folks, newbie here. Am impressed by the level of knowledge and discussion here. Appreciate some feedback on a scenario that has probably been asked in various forms before, but even after reading many posts, am not sophisticated enough to understand.

    In SDGE pricing EV-TOU2. Have an 6.0 kwh PV, NEM 1.0, 2 meters (one for house, one for EV). Am generating more than consumed, paying about $15/mo after all fees, so pretty close to net zero. In the past six months in summer, overall I generate 2000kwh total more than consumed (negative 300kwh/mo).

    I signed up for two PW2 with Swell back in Jan, level 1 SGIP. Total cost for 2 PW2 is $20k gross, minus rebates out of pocket is $8.5k. Final numbers are still not in since I haven't heard from them in months. But the overall cost seems high. I don't know that the ROI, if any, will offset this cost.

    From reading this forum, it seems that we cannot really sell back to the grid during peak hours due to existing PW2 software (or something like that). Given this is the case, from a cost analysis standpoint (besides backup power purposes), it seems that it does not make financial sense at this time.

    If rate structure changes in future and we can tweak PW2 to offload to grid at specific times, then the calculus changes, I presume?

    So bottom line:
    1) Does getting PW2 make financial sense?
    2) Is Swell doing shenanigans and overcharging for this project?
    3) Is SDG&E EV-TOU2 the best rate structure for me since I'm only drawing from the grid during super off peak period? I've read elsewhere that the DR-SES can be more advantageous.

    Many thanks in advance!
    -pb
     

    Attached Files:

  2. JGroeneweg

    JGroeneweg New Member

    Joined:
    Aug 16, 2016
    Messages:
    2
    Location:
    San Diego
    It seems to me that the PW software should be able to control the flow of the Kwh to and fro from the grid. This should allow for optimal use of the production you panels may be generating.

    For me, the benefit will be that, I will actually have oversight over what I am consuming (home, not cars) and what I am producing. Right now, it is on a honor system, SDGE+Tesla honor system... :( I really don't know since I have ONE meter...

    I have a similar setup. Looking forward what we can do. Remember the batteries will not feed to the cars, which are the big consumers!

    -JG
     
  3. WARP 10

    WARP 10 Member

    Joined:
    Sep 12, 2016
    Messages:
    95
    Location:
    San Diego
    Don't forget to include in your analysis the fact that unless you fall under NEM1.0 grandfathering (5yrs from the date you turned on your PV system), almost TOU-2 will begin implementation on Dec. 1. By 2019, except for the grandfathered NEM1.0 customers, everyone will be on TOU-2. TOU-2 changes both the peak times and seasons to be less beneficial to PV customers. Lots of info on both the SDGE and PUC web sites.
     
  4. miimura

    miimura Active Member

    Joined:
    Aug 21, 2013
    Messages:
    2,156
    Location:
    Los Altos, CA
    If I was generating more than I was using, I would not even consider a PowerWall. The grid is your battery. In your case, all a PowerWall will do for you is help you ride out power outages. How much is that worth to you?

    In my case, my solar is too small for my house and my two EVs. I pay about $1,000 per year in energy charges. By eliminating Peak usage I will eventually pay for the PowerWall(s) by avoiding some portion of those energy charges. I don't know exactly how much yet.
     
  5. Princeb

    Princeb Member

    Joined:
    Oct 7, 2017
    Messages:
    7
    Location:
    San diego
    Thanks for the replies!

    So under current rules, can I potentially use the PW2 to "make money" off of SDG&E to lower the overall cost of the project? Is this what they call "arbitrage"? It seems that if we can "program" the PW2 software to sell to the grid during peak and recharge during super-off peak, the average differential between rates under EV-TOU2 is something like $0.31 summer and $0.02 winter, per my calculation, with 2 PW2 27 kwh capacity, it will potentially "make" $4.45/day or $1600 a year. So in about 5 years, it will recoup the cost of the PW2 setup, assuming TOU/NEM1.0 remain constant.

    Also, is Swell price gouging? Seems Tesla/Solarcity cost for 2 PW is around $11k + install. Swell wants $20.5k incl install.
     
  6. miimura

    miimura Active Member

    Joined:
    Aug 21, 2013
    Messages:
    2,156
    Location:
    Los Altos, CA
    On the surface, the Swell Energy pricing looks like gouging. For the time being, I am giving them the benefit of the doubt. At initial presentation they told me that their price included the possibility of major upgrades and difficult installations. I have been confirmed in SGIP Step 1 with them, but have not seen a final contract with my final price. If it remains at the initial figure and they are unwilling to justify the costs or give me a more desirable but much more expensive install for that price, I will just give up my deposit and either give up on PowerWall for the time being or pursue other installation options.
     
  7. GenSao

    GenSao Member

    Joined:
    Aug 3, 2017
    Messages:
    21
    Location:
    Pleasant Hill, CA
    Swell Energy is really expensive. IMHO, the best price is to go though Tesla/Solar City directly. But if you are locked into SGIP Step one, then you may want to stay put (if you value the battery backup), For my pricing in the SF Bay area (gross numbers):

    • Swell Energy ($12,XXX = 1 Powerwall, $20,XXX = 2 Powerwall)
    • Solar City/Tesla = $7,693 = 1 Powerwall, $13,774= 2 Powerwall)
    The Intent of the SGIP program is to offset the solar "duck curve" and encourage self consumption. You can save money on a slight rate arbitrage of your utilities' time of use rate. Fill the battery with morning "off-peak power" to mitigate afternoon "peak power" use. If you produce more that the battery can store, you can still sell the excess to the utility. Useful when you are not home (working or vacation). You can then use the battery "off-peak power" during Peak power" and evening "off-peak power" usage. This is especially useful for users on one meter.

    For your particular use case (bottom line), it may not make sense to install a battery system since you are a net exporter and you already have a separate meter for EV use. Based on an out of pocket cost of $8,500, you would have to "save" an average of $850 a year over 10 years (warranty period). You'll have to make your own calculation, but there are estimates in the $300-$600 range out there.

    If you favor the whole house backup more and/or self-consumption, then it may be OK to still get the batteries.
     
  8. Tam

    Tam Active Member

    Joined:
    Nov 25, 2012
    Messages:
    2,933
    Location:
    Visalia, CA
    I have no experience but I have a vague idea.

    Yes. Charge your battery at night with cheap price and discharge your battery on daylight when the price is at its peak to take advantage of price difference which is what you call "arbitrage" so you can make money: buy low, sell high.

    I think you can make money in Europe but in the US, utilities do not want competition and they don't like the idea that homeowners would make money with electricity.

    They would have rules, laws, fees, psychological warfare (they call owners "grid parasites") to decrease a chance for a home owner to make money.

    For example, if it's solar, they would make sure to send their people out to inspect the size to make sure it is small enough so you cannot make a profit once it's activated.

    With battery, I think they might have a rule to negate the ability for owner's arbitrage as well. I am not sure, but they may switch to a pricing system that they charge you a lot for getting their electricity from the grid but they would pay you back very little from your battery so that in practice, you actually buy high and sell low which means the utilities would be the one that benefit from arbitrage or price difference, not you.
     
  9. drees

    drees Active Member

    Joined:
    Jun 23, 2009
    Messages:
    1,180
    Location:
    San Diego
    Under NEM rules, I do not think that you can export anything except solar energy. Historically, I believe this has held up residential storage project approvals by the utility as they wanted assurances that this couldn't be done.

    I wonder if this is what's delaying the release of TOU arbitrage settings for the Powerwall.

    Don't forget that the Powerwall 2 is about 90% efficient round trip. So if you put 10 kWh into it, you only get 9 kWh out. This almost wipes out any financial incentive for arbitrage in the winter (about $0.0056 / kWh) and reduces potential net profit in the summer from $0.306 / kWh to $0.256 / kWh.
     
  10. Princeb

    Princeb Member

    Joined:
    Oct 7, 2017
    Messages:
    7
    Location:
    San diego
    Can I keep my Sgi application locked in and switch from Swell to Solarcity?
     
  11. GenSao

    GenSao Member

    Joined:
    Aug 3, 2017
    Messages:
    21
    Location:
    Pleasant Hill, CA
    #11 GenSao, Oct 9, 2017
    Last edited: Oct 9, 2017
    Unlikely, but you would have to contact the SGIP program staff to confirm.

    Alternatively, you can try to apply yourself as a Developer and get the SGIP Rebate directly. Warning, it is a complicated processes. FYI, I am considering on doing it.
     

Share This Page