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

PG&E NEM true-up: yearly energy? or combined 12-month $$ total?

Discussion in 'Tesla Energy' started by rw99, Jul 20, 2018.

Tags:
  1. rw99

    rw99 Member

    Joined:
    Jul 11, 2017
    Messages:
    59
    Location:
    Bay Area
    Sorry for this simple question, but my searches have been fruitless.

    My system is installed on a cabin that sees typical seasonal use. High, on-peak summer usage that requires significant grid energy. Many days unoccupied during the rest of the year, with very low energy consumption.

    Just got my first NEM bill from PG&E, with a section titled "monthly NEM charges"... which made me worry that I have misunderstood the manner in which this program calculates the net balance due at true-up. Which of the below is true?

    1) The full year kWh generated is subtracted from full year kWh consumed. Any positive remainder in kWh is charged to me (at x rate?) at true-up. Any negative result (over-production) is credited at a much lower rate.

    2) A monthly NEM balance is generated, and charged according to on- and off-peak rates. These monthly NEM charges are then combined at true-up to determine the yearly settlement.

    I was expecting that our yearly total production would easily offset the high summertime draws from the grid. So scenario #2 would hurt: If our energy imbalance is instead being calculated and charged to us on a monthly basis, the true-up cost to me will be much higher.

    Thanks in advance for any help explaining this to me...
     
  2. commasign

    commasign Tesla Superfan

    Joined:
    Aug 31, 2013
    Messages:
    2,108
    Location:
    Davis, CA
    #2 commasign, Jul 20, 2018
    Last edited: Jul 20, 2018
    I may be oversimplifying (or overcomplicating, LOL) things but my understanding is #2 is correct IF you “spent” ($ credits) more than you “earned” ($ credits) but #1 is correct IF you “generated” (kWh) more than you “used” (kWh). Note that at annual true up, for #1, kWh is converted to $ at the wholesale rate (no TOU multipliers; just actual net kWh generated) whereas for #2, all $ accounting is done at retail rates (including TOU multipliers).

    #2 is most common. Few people have an oversized solar PV system that would result in #1.
     
  3. miimura

    miimura Active Member

    Joined:
    Aug 21, 2013
    Messages:
    3,109
    Location:
    Los Altos, CA
    #2. Each month the energy charges are calculated based on your rate schedule and the dollar amount is added to your true-up balance. You are also charged a Minimum Delivery Charge of about $10/mo that is due and payable on the "blue bill" every month. At true-up, you are credited for the Minimum Delivery charge already paid for any month where your actual delivery charges exceeded the minimum.

    What rate schedule are you on? E-1? E-6? E-TOU? EV? I don't understand what you're worried about. You still don't have to pay the high summer charges until the end of your annual true-up cycle and you have lots of unoccupied time during the rest of the year to generate credits for you.
     
  4. rw99

    rw99 Member

    Joined:
    Jul 11, 2017
    Messages:
    59
    Location:
    Bay Area
    I'm not worried... just disappointed. By this method, PG&E gets to immediately monetize the summer imbalance at high grid rates (including on-peak, when we spend weekdays there). Our unoccupied days of production in the off-season are pissed away as each monthly balance is monetized to me at that really low generator rate... in effect, the "net" computation is in dollars, not kWh. Which makes me think that this program shouldn't really be termed "net energy metering" :(

    It's more like net energy billing.

    Thanks for the info!


    Rich
     
  5. miimura

    miimura Active Member

    Joined:
    Aug 21, 2013
    Messages:
    3,109
    Location:
    Los Altos, CA
    I think you're misunderstanding it. The unoccupied days earn generation credits at RETAIL price that are tallied up on a monthly basis too. With Time of Use billing, you can generate an annual dollar credit balance quite easily. However, if you still use more kWh than you generate, you will not get that dollar credit back, it will be wiped out. That is a bummer. If you do generate more kWh than you use, then after your true-up you will be reimbursed for the surplus kWh at a very low rate, usually between 2.5 and 3.5 cents/kWh.
     
  6. rw99

    rw99 Member

    Joined:
    Jul 11, 2017
    Messages:
    59
    Location:
    Bay Area
    OK. So in October, let's say I produce 600 kWh. And we use only 100 kWh. You're saying that I get retail rate for the entire 600 I generated? Or just the 150 that matches what was consumed? If it's the latter case, then that excess 500 kWh in my favor is converted into very little money. And I'd need many more "producing" months to offset a single high-use month.

    Sorry if I'm being dense.
     
  7. siucity

    siucity Button Pusher

    Joined:
    Feb 18, 2015
    Messages:
    377
    Location:
    SF North Bay, CA
    Here's how it works. Let's assume a round number of $0.10/kWh that PG&E charges.

    For that month of October, you generated 500kWh more than you used. The running balance on your bill would be -$50, and your kWh balance would be -500kWh. Let's say November you used 200kWh more than you generated. Your running balance would then be -$30 (-$50 + $20), and your kWh balance would be -300kWh (-500kWh + 200kWh). At true-up time, your $ balance is what you owe if it's a positive balance. If it's negative, then look at your kWh balance. Take that number and multiply by something like $0.03/kWh. That's what you'd get back.
     
    • Like x 1
  8. cwied

    cwied Member

    Joined:
    Jan 13, 2015
    Messages:
    393
    Location:
    San Mateo, CA
    Yes, you're credited the retail rate for the whole 600 kWh. It's only at true-up time that the wholesale rate comes into play and then only if you are a net generator from the kWh perspective.
     
  9. miimura

    miimura Active Member

    Joined:
    Aug 21, 2013
    Messages:
    3,109
    Location:
    Los Altos, CA
    Let's take your example and assume that you're on the default tiered plan, E-1 (which would be stupid with solar, but it's easier to calculate).
    Generation: 600kWh
    Consumption: 100kWh
    Net: -500kWh

    Baseline: 10.1kWh/day = 303 kWh baseline (30 days)
    -303kWh * $0.21169 = -$64.14
    (-500 + 303)kWh * $0.27993 = -$55.14
    Total added to true-up for October: -$119.28

    Here's a snapshot of one of my old bills before I was on the CCA.
    PG&E NEM Example_B.jpg

    PG&E NEM Example.jpg
    In the first section you see that in total, the meter registered 457.6kWh of net generation and 750.5kWh of net consumption. Those are the sums of the instantaneous positive and negative values. Whatever you generate and consume before it gets to the meter doesn't count.

    In the second section, you can see the breakdown by TOU period. During the Peak and Part-Peak periods I generated more than I consumed, which earned me credits at retail rates. During the Off-Peak period, there is only solar generation on weekends and I charged my cars overnight, so I was a big consumer during that period. So, even with a net usage of almost 292.9kWh, I earned a bill credit of $4.39. However, there are those pesky minimum charges, so I still paid $10.51 that month.
     
  10. rw99

    rw99 Member

    Joined:
    Jul 11, 2017
    Messages:
    59
    Location:
    Bay Area
    Thanks, all... great input and encouraging discussion.

    Can I also mea culpa a post with faulty arithmetic? Jeebus. To set the record straight, 600 minus 500 equals 100. Thank you for not beating me over the head as was deserved.

    I need a weekend!!!
     
  11. NoMercy4You

    NoMercy4You Member

    Joined:
    Jul 2, 2018
    Messages:
    6
    Location:
    Fresno

    What rate are you on for PG&E? Trying to figure out what plan to choose from makes me dizzy. We are on tiered one now and looking to move to a TOU plan and we have solar as well. Eventually looking to charge the car at night, like you, so hopefully tons of usage at the very low rate :).
     
  12. NoMercy4You

    NoMercy4You Member

    Joined:
    Jul 2, 2018
    Messages:
    6
    Location:
    Fresno
    Scratch that I see your on the EV-A rate.
     
  13. cpa

    cpa Active Member

    Joined:
    May 17, 2014
    Messages:
    2,050
    Location:
    Central Valley
    If you can figure out how TOU is cheaper than tiered rates here in Fresno without overbuilding your solar array, please advise.

    I ran a couple of simple comparisons, and we would get hosed with TOU rates between Father's Day and Labor Day. The surplus generated in early May and late September just does not begin to offset the large usage between 3:30 and 7:30 each afternoon, day after day after day.

    Our most recent true-up with a Model S for the entire year plus our Model 3 for six months was $377. We have a 4,400-watt system on our roof with a 2,350 ft^2 home. Our true up would be lower but for some large trees that begin to shade the panels after the autumnal equinox around 3:00 each day.
     
  14. miimura

    miimura Active Member

    Joined:
    Aug 21, 2013
    Messages:
    3,109
    Location:
    Los Altos, CA
    If you have significant AC use because you're in the East Bay or Central Valley, the Peak period in the EV rate can really bite you hard. For almost everyone else charging a car overnight, the EV rate is cheaper than the E-1 tiered rate, usually by a large margin. However, within a few years, everyone will be pushed into some kind of TOU rate in PG&E territory.
     
  15. NoMercy4You

    NoMercy4You Member

    Joined:
    Jul 2, 2018
    Messages:
    6
    Location:
    Fresno
    I ran the analysis on the My PGE ios app that was referenced. It will be cheaper for me to change to a EV-A rate. I have only had solar for 2 months mind you, a 6.5KW array with about 1.9K sq ft house no trees. Right now we produce excess power at the highest tier and most of our usage comes at around 8pm to midnight where the AC is still pumping to keep the house cool and the sun is long gone.

    I think you may have to add more solar to solve your problem without it generating excess power during noon and later, you will have a difficult time making the numbers work out for you.
     
  16. cpa

    cpa Active Member

    Joined:
    May 17, 2014
    Messages:
    2,050
    Location:
    Central Valley
    Thank you, NoMercy. I had expected that adding another 1,500 watts or so would likely do the trick. But I cannot seem to justify the additional expense vis-a-vis utility savings if our true up bill each year will be under $500.

    But then, we have the little game that PG&E plays by shifting the TOU intervals. As more rooftop solar is installed, that will just mean that PG&E is not providing as much electricity during the mid-afternoon periods. So, rather than a 2-8 PM peak period, they will shift the peak period to 5-11 when solar production begins to wane significantly but the temperatures are still >90, and many people are still running their AC.
     
  17. Shygar

    Shygar Member

    Joined:
    Aug 7, 2017
    Messages:
    661
    Location:
    Pleasant Hill, CA
    That's what powerwalls are for. Use cheaper energy during your peak rates while you export 100% of your solar.
     
  18. NoMercy4You

    NoMercy4You Member

    Joined:
    Jul 2, 2018
    Messages:
    6
    Location:
    Fresno
    He is trying to maximize his peak solar production enough to offset some of the peak and offpeak usage after the sun goes down. Anything extra is simply icing for offpeak charging. In his case, it makes more sense to invest the money into adding more panels than to install a powerwall. They are pretty expensive atm, maybe in the future when they are more affordable it would be a no-brainer.
     

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