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

NEM 2.0 vs NEMMT

Discussion in 'Tesla Energy' started by Magiken, Aug 14, 2018.

  1. Magiken

    Magiken Member

    Joined:
    Aug 14, 2018
    Messages:
    11
    Location:
    California
    We're adding a second system(with PWs) and the question has come in as to if we want to keep the original system on NEM 1.0 or convert it to NEM 2.0 with the new system. I can find very little opinion/feedback on this but the one study I did find seemed to lean towards the 2.0 option. Do any of you have any wise words?
     
  2. cwied

    cwied Member

    Joined:
    Jan 13, 2015
    Messages:
    400
    Location:
    San Mateo, CA
    I can't think of a reason why NEM 2.0 would be advantageous over NEM 1.0 presuming that you can install the same system if you keep the old system on NEM 1.0. What are the reasons given for switching to 2.0? It would seem to me that you end paying more NBCs if you do so. Is it a metering issue?
     
  3. Magiken

    Magiken Member

    Joined:
    Aug 14, 2018
    Messages:
    11
    Location:
    California
    Here's the explanation given for the two options:
    (1) NEMMT (NEM Multiple Tariff)
    Maintain your original system including currently locked-in rates under NEM 1.0 for the remainder of your allowed 20 years while adding the new generation (system) under NEM 2.0 by installing a Net Generation Output Meter (NGOM) at your own expense, which can cost up to $6,000. You will essentially own two systems, each running on its own separate meter per assigned NEM tariff. This option will "grandfather" the NEM 2.0 system under the NEM 2.0 tariff for a full 20 years, beginning from the issuance of the PTO (permission to operate) for this project. Utility states estimated cost for customer that will be determined by the utility. This option will not be financed by Tesla in any way.

    OR

    (2) NEM2
    Place both the original NEM 1.0 system and the added generation under the NEM 2.0 tariff. Choosing this option preserves the original PTO date from the NEM 1.0 system as relates to the grandfathering provision. Both systems will function together per NEM 2.0 regulations and tariff. There are no added costs for this option.
     
  4. Az_Rael

    Az_Rael Supporting Member

    Joined:
    Jan 26, 2016
    Messages:
    3,843
    Location:
    Palmdale, CA
    I think the nom bypassable charges are the big thing. We are on NEM 2.0 and even though I currently have a $300 credit with the power company, I still have to pay them $34/month.
     
    • Informative x 2
  5. Magiken

    Magiken Member

    Joined:
    Aug 14, 2018
    Messages:
    11
    Location:
    California
  6. cwied

    cwied Member

    Joined:
    Jan 13, 2015
    Messages:
    400
    Location:
    San Mateo, CA
    Ah ok. If you have to install a second meter, I'm guessing that will be far more expensive than what you would save in NBCs. You could try getting a quote for that, as that would probably be the deciding factor.
     
  7. Magiken

    Magiken Member

    Joined:
    Aug 14, 2018
    Messages:
    11
    Location:
    California
    Agreed. We just asked for the specific amount.
     
  8. kev1n

    kev1n Member

    Joined:
    Nov 17, 2016
    Messages:
    742
    Location:
    Bay Area
    NEM 1.0 is better than NEM 2.0

    you will have to do some math to figure out if a new meter will cost you more in the long run than the savings you get for having one system on NEM 1.0

    they will not allow you to just add onto the current system with NEM 1.0? is it due to the size of the 2nd system?
     
  9. Magiken

    Magiken Member

    Joined:
    Aug 14, 2018
    Messages:
    11
    Location:
    California
    NEM 1.0 is no longer in use, as of July 2017. So your only options are those above, unless your system is over 1 MW, then there are some additional rules.
     
  10. wwhitney

    wwhitney Member

    Joined:
    Nov 2, 2017
    Messages:
    280
    Location:
    Berkeley, CA
    #10 wwhitney, Aug 14, 2018
    Last edited: Aug 14, 2018
    OK, here's my understanding:

    With NEM 1.0, the monthly bill is determined by looking at the total net usage within a given TOU category and calculating the debit/credit accordingly. NEM 2.0, in contrast, requires looking all of the interval data (every 15 minutes, I think) within the given TOU category, and you get a slightly lower credit for the intervals showing net export than the debit you pay for the intervals showing net usage. The difference in rates reflects the Non-Bypassable Charges, a fee for the power company delivering energy to you during one interval that you don't get credited back when you deliver energy to the power company during another interval.

    With an existing NEM 1.0 generator, you are limited in how much generation you can add and stay under NEM 1.0. The limit is 1.0 kW, or for systems bigger than 10 kW, 10% of the system size. If you add more generation than that, the new generation has to be under NEM 2.0. So one option is just to switch everything over to NEM 2.0.

    The other option is to maintain separate NEM 1.0 and NEM 2.0 systems, but this requires a second meter (called a Net Generation Output Meter, NGOM). I don't know if the utility side of the NGOM is typically connected before or after the main meter, but in terms of data capture, it doesn't matter; the two are equivalent via some subtraction.

    More to follow; I'm actually on hold with PG&E trying to find out how the NBCs work when you have two meters and both a NEM 1.0 system and a NEM 2.0 system.

    Cheers, Wayne
     
  11. kev1n

    kev1n Member

    Joined:
    Nov 17, 2016
    Messages:
    742
    Location:
    Bay Area
    i understand its no longer available but if im understanding this correctly, making any change at all to a NEM 1.0 system means you have to move to 2.0 aside from adding a new meter?
     
  12. liuping

    liuping Active Member

    Joined:
    Jul 23, 2013
    Messages:
    2,115
    Location:
    San Diego
    You can only add up to 10% more to an existing system to stay in NEM 1.0.
     
    • Informative x 1
  13. wwhitney

    wwhitney Member

    Joined:
    Nov 2, 2017
    Messages:
    280
    Location:
    Berkeley, CA
    It's the greater of 1 kW of 10% of the existing system size.

    Cheers, Wayne
     
  14. wwhitney

    wwhitney Member

    Joined:
    Nov 2, 2017
    Messages:
    280
    Location:
    Berkeley, CA
    OK, 45 minutes and 3 people at PG&E Solar Customer Service Center failed to provide an answer on how NBCs work with two meters and a joint NEM 1.0 / NEM 2.0 system. Perhaps I will hear back from them as promised.

    Here's my guess, but there are a number of other possibilities:

    Call the old meter A; it shows (NEM 1.0 generation - consumption), where net generation is positive (opposite the usual convention). Call the new meter B; it shows the NEM 2.0 generation (also positive). And call the total T = A+B.

    If T is negative (net consumption) for an interval, you are charged at the full retail rate for the consumption.
    If T is positive (net generation) for an interval, and T < B, then you are credited at the reduced retail rate for the NEM 2.0 generation.
    If T is positive for an interval and T > B, then you are credited B at the reduced retail rate for NEM 2.0 generation, and (T-B) at the full retail rate for NEM 1.0 generation.

    Again, this is only a guess, but it seems to me that it is the only semi-reasonable algorithm when the new meter just meters the NEM 2.0 system production.

    Cheers, Wayne
     
  15. GenSao

    GenSao Member

    Joined:
    Aug 3, 2017
    Messages:
    170
    Location:
    Pleasant Hill, CA
    Agreed. From what I have read NEM 1.0 is generally better than NEM 2.0 from a pure solar panel only prospective. Since a new meter is needed for part of your system to stay on the old rate schedule with NEM 1.0, moving to a new rate schedule with NEM 2.0 may be more cost effective. Your specific utility rate schedule will dictate the cost effectiveness.

    I am in PG&E Land. The most cost effective would be on an EV rate schedule (EV-A) with solar and batteries mitigating the peak (Summer $0.455/kWh) and partial-peak rate (Summer $0.251/kWh). I shift power use to off-peak rate (Summer $0.123/kWh) to night to charge EVs, dry laundry, and charge other batteries.

    For PG&E, non-bypass charges are approximately $0.0211/kWh based on:

    $ 0.0141 Public Purpose Program Charge
    $ 0.0002 Nuclear Decommissioning Charge
    $ 0.0013 Competition Transition Charge
    $ 0.0055 Department of Water Resources Bond Charges​

    Do consider the cost of round-trip power loss of 11% (100% - 89% Efficiency) for a Powerwall to defer non-bypass charges at partial-peak or off peak rates. In general you'll still come out ahead.

    Partial-peak rate, Summer $0.251/kWh x 11% = $0.0276/kWh
    Off-peak rate, Summer $0.123/kWh x 11% = $0.0135/kWh​

    Furthermore, participation in demand response programs such as Ohmconnect may be useful to you. If interested, a referral link is provided. It is not required to sign up.
     
  16. wwhitney

    wwhitney Member

    Joined:
    Nov 2, 2017
    Messages:
    280
    Location:
    Berkeley, CA
    P.S. Upon reflection, the algorithm I propose is fair, in the sense that it makes an existing NEM 1.0 customer's incentive to add solar the same as any new NEM 2.0 customer. Namely, generation that offsets existing consumption reduces one's bill at the full retail rate, while generation that leads to export is credited at the NEM 2.0 reduced retail rate.

    So that is probably how it works.

    Cheers, Wayne
     
  17. Magiken

    Magiken Member

    Joined:
    Aug 14, 2018
    Messages:
    11
    Location:
    California
    Thanks GenSao and wwhitney for the info. This is very helpful. We certainly sympathize with trying to get a clear answer out of anyone at PG&E, or Tesla for that matter. And yes, we also recognize the EV plan and when we use power is probably the biggest variable here that will ultimately determine 'success' versus the NEM choice.
     
  18. wwhitney

    wwhitney Member

    Joined:
    Nov 2, 2017
    Messages:
    280
    Location:
    Berkeley, CA
    OK, now I'm not sure how NBCs work. So here's a simple example:

    Say there's just 1 tier/TOU category and a billing period with only 2 non-zero intervals. The total rate is $0.10/kWh, of which NBCs are $0.02/kWh. If one interval shows 3 kWhs produced, and the other interval shows 3 kWhs consumed, then obviously the charge is $0.06, just from the NBCs. Now change the production figure to 2 kWhs, keeping the consumption figure at 3 kWhs. Is the bill $0.14 (that is, 3 * $0.10 - 2 * $0.08), or is the bill $0.10 (that is, max((3-2) * $0.10, 3 * $0.02))?

    My previous comments were based on the understanding it would be $0.14, so if it would actually be $0.10, I'll need to reconsider everything.

    Cheers, Wayne
     
  19. GenSao

    GenSao Member

    Joined:
    Aug 3, 2017
    Messages:
    170
    Location:
    Pleasant Hill, CA
    Using your example under NEM 2:

    3 kWh consumed ($0.10 + $0.02) x 3 = $0.36; Less 3 kWh produced ($0.10) x 3 = $0.30; Equals $0.36 - $0.30 = $0.06 Charge
    3 kWh consumed ($0.10 + $0.02) x 3 = $0.36; Less 2 kWh produced ($0.10) x 2 = $0.20; Equals $0.36 - $0.20 = $0.16 Charge

    For refrence, under NEM 1:

    3 kWh consumed ($0.10 + $0.02) x 3 = $0.36; Less 3 kWh produced ($0.10 + $0.02) x 3 = $0.36; Equals $0.36 - $0.36 = $0.00 Charge
    3 kWh consumed ($0.10 + $0.02) x 3 = $0.36; Less 2 kWh produced ($0.10 + $0.02) x 2 = $0.24; Equals $0.36 - $0.24 = $0.12 Charge

    Non bypass charges are fees that can not be reversed by solar generation credits.
     
  20. NuShrike

    NuShrike Member

    Joined:
    Nov 13, 2017
    Messages:
    205
    Location:
    SoCal
    GenSao's numbers are correct.

    Under NEM 2.0, the actual rates are:
    $0.10/kWh for production, $0.12/kWh for consumption
    So: -$0.30 + $0.36 = $0.06 v -$0.20 + $0.36 = $0.16

    For us under SCE (TOU-A summer):
    off-peak: consumption: $0.12382 v generation: $0.10463
    shoulder: consumption: $0.27646 vs generation: $0.25727
    peak: consumption: $0.47929 vs generation $0.4601

    Solution is to arbitrage against the peak generation rate by converting off-peak kWh -- to offset monthly NBCs.
     
    • Helpful x 1

Share This Page

  • About Us

    Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.
  • Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


    SUPPORT TMC