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SDG&E rate sanity check - Tools to help with PVWatt request

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  • SDG&E rate sanity check - Tools to help with PVWatt request

    I followed the suggestion in post #3 here (https://www.solarpaneltalk.com/forum...tou-vs-non-tou) and built out a spread sheet for my last year of SDG&E electric use (thanks JPM!).

    Using PVWatt I had to eyeball my azimuth and roof pitch. Are there tools online to help me get these figures more accurate?

    Once Excel spit out the results I had to go back and double check my work. I'm on Schedule DR which is basic two tier use. I've checked the SDG&E calculator and it has always said the TOU was the same or some were about 5% less. However with my 12 month actual usage plugged into the DR-SES rate, a rate which is only available to Solar households my bill shows 1/3 lower than I paid under Schedule DR. Can this be right? I with the PVWatt solar generation numbers I backed into a system size that is close to what several installers recommended to get 90-100% offset so it seems like this should be right. But it doesn't make sense to me that the DR-SES rate plan would be so much cheaper.

    So sanity check request-does my result fit with what other San Diego folks have calculated in the past?

  • #2
    Short ans. is yes, "maybe". I just had rt. elbow surg., any my typing will be much abbreviated for ~~ 2 wks. or so. I'll prevail on Sensij to fill you in on a FEW of the details of possible benefits T.O.U. vs. tiered rates if he'd be so kind.

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    • #3
      Originally posted by J.P.M. View Post
      Short ans. is yes, "maybe". I just had rt. elbow surg., any my typing will be much abbreviated for ~~ 2 wks. or so. I'll prevail on Sensij to fill you in on a FEW of the details of possible benefits T.O.U. vs. tiered rates if he'd be so kind.
      I can't write much tonight, but would just caution the OP to make sure the *newly approved* TOU hours are what is being modeled, not the hours effective today. Moving peak from 12-6 to 4-9 and shortening summer to 5 months are two solar unfriendly changes to consider.

      More tomorrow, with links to some other discussions on this. (Google search TOU site:www.solarpaneltalk.com)
      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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      • #4
        Sensij and JPM, thank you for all of your helpful activity on this forum. JPM, good luck in your recovery from surgery. I've actually been lurking since early this year and have read quite a bit about the rates but that is not the same as understanding. I've also seen JPM argue the SG&E tools are less than accurate and with some rate plans that remain very difficult to model (and that most people mess it up) so wanted to see if i've made a basic mistake in my math. I feel like I think I know enough to get answers but probably am just dangerously over confident I understand how billing works.

        Where I am now: I downloaded my usage for the past 12 months broken down by the hour (couldn't find 15 minutes) and plugged it into the same revenue spreadsheet I'd made using PVWatts hourly data. Result was an annual bill that was 30% less than I actually paid-which implies that if I put one solar panel up to qualify for that rate plan my bill would drop 30%-that doesn't seem possible.

        I've read the threads about the TOU time periods changing going forward and am going to model that next. But if I can get install and permission to operate before 12/1/2017 it appears that I can sign up for the current DR-SES plan with current time windows. (https://www.sdge.com/clean-energy/ti...ring-customers) Is that not right? And I modeled peak as 11-6pm in the summer but you reference 12-6pm. I work at home so am not sure TOU is right for me anyhow-if you can point me to a thread that discusses the method to accurately model DR-Standard projections with solar production I'd like to take a crack at that as well. If that plan is better then I can wait until 3/30/18 to get PTO.

        The two threads I've been mainly referencing for my spread sheet work are: https://www.solarpaneltalk.com/forum...tou-vs-non-tou and https://www.solarpaneltalk.com/forum...r-net-metering

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        • #5
          Originally posted by so_cal_burbs View Post

          Where I am now: I downloaded my usage for the past 12 months broken down by the hour (couldn't find 15 minutes) and plugged it into the same revenue spreadsheet I'd made using PVWatts hourly data. Result was an annual bill that was 30% less than I actually paid-which implies that if I put one solar panel up to qualify for that rate plan my bill would drop 30%-that doesn't seem possible.

          I've read the threads about the TOU time periods changing going forward and am going to model that next. But if I can get install and permission to operate before 12/1/2017 it appears that I can sign up for the current DR-SES plan with current time windows. (https://www.sdge.com/clean-energy/ti...ring-customers) Is that not right? And I modeled peak as 11-6pm in the summer but you reference 12-6pm. I work at home so am not sure TOU is right for me anyhow-if you can point me to a thread that discusses the method to accurately model DR-Standard projections with solar production I'd like to take a crack at that as well. If that plan is better then I can wait until 3/30/18 to get PTO.

          The two threads I've been mainly referencing for my spread sheet work are: https://www.solarpaneltalk.com/forum...tou-vs-non-tou and https://www.solarpaneltalk.com/forum...r-net-metering
          My 12-6 comment was based on the EV-TOU-2 plan, sorry for the confusion. Yes, 11-6 is correct for DR-SES. And, yes, a 30% drop is believable, if your consumption from 11-6pm on weekdays is not high. If you'd like for me to review your spreadsheet for errors, you can post a link to it here (dropbox?), or I can contact you privately.

          That is a great link describing the grandfathering complexities, I hadn't seen it summed up like that before. I agree that the way they wrote it there, 5 year grandfathering if you get in before 12/1/17 looks correct.

          Modeling DR is a little more complicated in that you need to look at loads and generation together to figure out what tier of electricity you are in, but since the tiers are evaluated over no more than a monthly basis, it isn't too bad to calculate.
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

          Comment


          • #6
            Originally posted by sensij View Post

            My 12-6 comment was based on the EV-TOU-2 plan, sorry for the confusion. Yes, 11-6 is correct for DR-SES. And, yes, a 30% drop is believable, if your consumption from 11-6pm on weekdays is not high. If you'd like for me to review your spreadsheet for errors, you can post a link to it here (dropbox?), or I can contact you privately.

            That is a great link describing the grandfathering complexities, I hadn't seen it summed up like that before. I agree that the way they wrote it there, 5 year grandfathering if you get in before 12/1/17 looks correct.

            Modeling DR is a little more complicated in that you need to look at loads and generation together to figure out what tier of electricity you are in, but since the tiers are evaluated over no more than a monthly basis, it isn't too bad to calculate.
            That SDG & E link has been around for a while but I think it's been changed slightly to include the 12/01/2017 grandfathering date. That link was the written confirmation to the verbal assurances I got that NEM 1.0 customers on tiered rates would be able to stay on tiered rates but doing so would require a positive written customer election to do so. If/until an EV shows up in my garage I'll probably be on tiered rates as long as there is a tiered schedule.

            Sensij,, as you know, at this time, for SDG & E users, DR-SES an EV-TOU-2 tariff rates are not linked to kWh usage quantity per billing period. So, I'll make another pitch and state that for those 2 schedules, it's possible to get a meaningful metric by treating a PV system as a revenue generator that, with assumptions of < 100 % usage off set and an estimate of a system's (or 1 kW of a system) hourly annual output, it's an easier job to get a cost effective size. It's also a lot easier to compare the financial effects of changing or comparing orientations for the purpose of squeezing the most cost effectiveness out of an array.

            Also, by comparing revenue generated under the old and new times for DR-SES and EV-TOU-2 (or any schedule whose rates are not linked to the quantity of usage per billing period), it's easy to see the effect that the new times will have on system cost effectiveness when used against the DR-SES an EV-TOU2 schedules. If nothing else, that could be another negotiating tool, as in: "Look Mr. vendor, the new DR-SES times just made your proposed system ~~ 20-25% less cost effective. You better sharpen your pencil."

            On bill calculation under the old DR tiered schedule (and I hope for me as an NEM 1.0 grandfathered user), I've got that billing pretty much dialed in, but it's so intertwined with my model that generates system output of ~~ 100 mega byte spreadsheet, making it difficult to transmit. FWIW,I didn't have a very difficult time figuring out the bill with or without PV. The devil was in the details, but it was a very good learning experience.

            Finally, this 1 handed typing thing, while a PITA, ain't as bad as I thought, probably made easier by the pain meds.
            Last edited by J.P.M.; 09-06-2017, 11:26 PM.

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            • #7
              So my understanding is designing a system to offset my bill is something we can target for the next five years based on new systems being grandfathered into NEM 2.0. However once those five years are up we (new installs/NEM 2.0 people) will be forced to move onto whatever TOU plan is in place at that time. Making predicting payback after five years a shot in the dark, correct?

              At one time I thought there was an opinion that a system that offsets 100% of usage would only be billed $10/month. But with NBC I believe it would be $10/month plus around .02 per kilowatt delivered to the house. With 100% offset on tiered rates that would be that. With TOU then the spreadsheet needs to be deployed which may or may not show the same level of financial offset as tiered rates. Am I understanding correctly?

              I see Sullivan is now advertising a 'free battery' with every install and claim that the battery will 'increase solar savings'. (yes, JPM I know it isn't really free-save your typing) I've read on this board many people shooting down batteries but I've also read some sites that claim only Hawaii and San Diego make sense for battery (or at least come close). Has anyone seen the Sullivan sales pitch on this? I'm curious how they sell it. If no-one has seen it yet I'll set up an appointment for a quote and report back.

              I'm guessing batteries don't make sense yet, but if I want to anticipate adding them later should it affect my plan on the initial system? I'm guessing whatever inverter today that supports a battery will probably be incompatible with new batteries in 5 years. If I go solar this year and add batteries in a future year can I submit Tax Credits for each project? I assume so but haven't been able to find a site that spells it out explicitly.

              Comment


              • #8
                Originally posted by so_cal_burbs View Post
                So my understanding is designing a system to offset my bill is something we can target for the next five years based on new systems being grandfathered into NEM 2.0. However once those five years are up we (new installs/NEM 2.0 people) will be forced to move onto whatever TOU plan is in place at that time. Making predicting payback after five years a shot in the dark, correct?

                At one time I thought there was an opinion that a system that offsets 100% of usage would only be billed $10/month. But with NBC I believe it would be $10/month plus around .02 per kilowatt delivered to the house. With 100% offset on tiered rates that would be that. With TOU then the spreadsheet needs to be deployed which may or may not show the same level of financial offset as tiered rates. Am I understanding correctly?

                I see Sullivan is now advertising a 'free battery' with every install and claim that the battery will 'increase solar savings'. (yes, JPM I know it isn't really free-save your typing) I've read on this board many people shooting down batteries but I've also read some sites that claim only Hawaii and San Diego make sense for battery (or at least come close). Has anyone seen the Sullivan sales pitch on this? I'm curious how they sell it. If no-one has seen it yet I'll set up an appointment for a quote and report back.

                I'm guessing batteries don't make sense yet, but if I want to anticipate adding them later should it affect my plan on the initial system? I'm guessing whatever inverter today that supports a battery will probably be incompatible with new batteries in 5 years. If I go solar this year and add batteries in a future year can I submit Tax Credits for each project? I assume so but haven't been able to find a site that spells it out explicitly.
                Well, that's more than an opinion about the resulting bill a 100 % offset system will be. As you state it, it's a fact. But it says nothing about the cost effectiveness of a 100 % or 100+ % offset.

                Whether or not battery storage makes (financial) sense anywhere is a f(particulars) of the application. At this time, most residential PV applications will be less cost effective with battery backup, including those in San Diego and environs. Battery backup may or may not make sense anywhere, mostly, at this time, and using any reasonable set of criteria (and that includes <25 yr. lifecycles), it's looking like the LCOS (Levilized Cost of Storage) is running quite a bit higher than peak rate electricity from SDG & E. That would put battery storage in the less than economically viable category of options for me at this time.

                Seems that, as usual and continuing, most folks get PV with the idea of reducing their energy bills and wind up spending more for the PV than the PV reduces the electric bills in any usual and realistic NPV analysis, and now will tend to compound the situation by considering storage that's technically unproven and, on top of that, even less cost effective than most of the residential PV I see.

                But, Not my house/life/money. If it wasn't such a waste, it would be comical.

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