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Migrating from NEM 1.0 to NEM 2.0 (NEM-ST) - SDG&e

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  • #31
    My grid tied PV system is 6.4 kW with SDG&E and has produced over 10,000 kWh's over the past year. I have just finished my first true-up period on my system which started in Sept 2016 and ended Aug 29, 2017. I opted into TOU Plus for one year with a guaranteed refund if it cost more than the Standard DR rate. My system was designed to zero out my electric bill and I ended with over 3400 kWh's. Here is the comparison between the TOU and Standard DR rates:
    1 year no-risk sdg&e pricing.PNG
    As you can see the differenc is $32.34 in favor of TUO plus over standard DR. There are two large differences. One in April and one in August. The former is due to the California Climate Credit in April and the difference in compensation for excess generation in August. You will note that the charges for the other months differ by only a few cents or are equal.
    Last edited by lwsmiser; 09-10-2017, 01:27 AM.

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    • #32
      Originally posted by lwsmiser View Post
      ...and I ended with over 3400 kWh's.
      You can use this to power a(nother) EV!

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      • #33
        Originally posted by lwsmiser View Post
        My grid tied PV system is 6.4 kW with SDG&E and has produced over 10,000 kWh's over the past year. I have just finished my first true-up period on my system which started in Sept 2016 and ended Aug 29, 2017. I opted into TOU Plus for one year with a guaranteed refund if it cost more than the Standard DR rate. My system was designed to zero out my electric bill and I ended with over 3400 kWh's. Here is the comparison between the TOU and Standard DR rates:
        1 year no-risk sdg&e pricing.PNG
        As you can see the differenc is $32.34 in favor of TUO plus over standard DR. There are two large differences. One in April and one in August. The former is due to the California Climate Credit in April and the difference in compensation for excess generation in August. You will note that the charges for the other months differ by only a few cents or are equal.
        And at current overgeneration compensation of ~ $0.027/excess generation compensation/kWh, you made $0.027*3400 = $91.80 as a payment on about $7,000 *.70 = $4,900 worth of purchased excess generating capacity.

        Congrads on your $91.8/$4,900 = 1.87 % investment coup.

        A fine example of the effects and joys of oversizing.
        Last edited by J.P.M.; 09-10-2017, 10:43 PM.

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        • #34
          Originally posted by J.P.M. View Post

          And at current overgeneration compensation of ~ $0.027/excess generation compensation/kWh, you made $0.027*3400 = $91.80 as a payment on about $7,000 *.70 = $4,900 worth of purchased excess generating capacity.

          Congrads on your $91.8/$4,900 = 1.87 % investment coup.

          A fine example of the effects and joys of oversizing.
          Hence, my suggestion to use the system to its fullest. Using the 3400 kWh to drive an EV 12,000+ miles would save about $1,500 in gas alone, per year. Since you can charge during super off peak, you'll net more energy, in fact.

          Would you mind adjusting the return on investment using those figures?

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          • #35
            Originally posted by bstr View Post

            Hence, my suggestion to use the system to its fullest. Using the 3400 kWh to drive an EV 12,000+ miles would save about $1,500 in gas alone, per year. Since you can charge during super off peak, you'll net more energy, in fact.

            Would you mind adjusting the return on investment using those figures?
            That may be hard to provide since all EV's will use more kWh to recharge as their battery degrades. Along with the price of gas changing and the depreciation of the EV over it's lifetime hard to determine the cost against the savings.

            There is also the possibility that super off peak rates may change. Too many variables to determine a solid ROI for solar charging an EV.

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            • #36
              Originally posted by bstr View Post

              Hence, my suggestion to use the system to its fullest. Using the 3400 kWh to drive an EV 12,000+ miles would save about $1,500 in gas alone, per year. Since you can charge during super off peak, you'll net more energy, in fact.

              Would you mind adjusting the return on investment using those figures?
              You would need to add in the cost of the EV itself (and insurance), or at least the difference relative to the most cost-effective ICE alternative, if you want to include gasoline offset in your return calculations.

              I think that it is generally a losing game to try to justify an oversized array by intentionally shifting energy consumption from other sources to electricity. It may be appropriate given the sunk cost of the PV system, but you are more likely to be making lemonade than achieving the best case financial outcome that would have been available with a smaller PV expense.

              CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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              • #37
                Originally posted by SunEagle View Post

                That may be hard to provide since all EV's will use more kWh to recharge as their battery degrades. Along with the price of gas changing and the depreciation of the EV over it's lifetime hard to determine the cost against the savings.

                There is also the possibility that super off peak rates may change. Too many variables to determine a solid ROI for solar charging an EV.
                I'm not sure where you are getting the idea that an EV becomes less efficient to drive over time. The battery capacity will fall, but if the car is properly maintained, the same 40 mi commute (for example) should consume the same amount of energy, and take the same amount of energy to recharge.

                Some sort of estimation of what electricity rates will do over time is necessary for any financial justification of a PV system. I doubt that focusing on super off peak rates specifically is any more or less accurate than any other estimate that might be used.

                Without doing any research, I'd guess that gas prices are more volatile than electricity, but there is probably a sufficiently conservative number that could be used to perform an estimate.

                Vehicle depreciation can be a factor, but if the comparison is made on leasing costs (EV vs ICE), that can be a way to dodge that bullet, and conveniently sets the time period over which the analysis should be run.
                CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                • #38
                  Originally posted by sensij View Post

                  I'm not sure where you are getting the idea that an EV becomes less efficient to drive over time. The battery capacity will fall, but if the car is properly maintained, the same 40 mi commute (for example) should consume the same amount of energy, and take the same amount of energy to recharge.

                  Some sort of estimation of what electricity rates will do over time is necessary for any financial justification of a PV system. I doubt that focusing on super off peak rates specifically is any more or less accurate than any other estimate that might be used.

                  Without doing any research, I'd guess that gas prices are more volatile than electricity, but there is probably a sufficiently conservative number that could be used to perform an estimate.

                  Vehicle depreciation can be a factor, but if the comparison is made on leasing costs (EV vs ICE), that can be a way to dodge that bullet, and conveniently sets the time period over which the analysis should be run.
                  SunEagle and Sensij, I'm only suggesting using excess production in a way that will benefit the owner more so than the 2.78 cents/kWh return. By the way, degradation studies show this is not a great concern and gas cars also lose efficiency. For this example, using a 3 year lease at a fixed cost with unlimited miles and 20 cents/kwh charging reimbursement (4.44 cents/mile actual) might show the return more clearly.

                  Driving 12,000 miles per year at 24 mpg (real world actual average when the sticker says 30 mpg) and $3.00 per gallon would cost $1,500
                  The Hyundai Ioniq has a 3 year lease for $275, call it $300 total, with unlimited miles. Driving it 12000 miles, you would get a credit of $533 per year (44/mo) in charging reimbursement. The more you drive, the more you get back, up to 50k miles.

                  So there you have it. That's my best suggestion for using the excess production for the most gain. If there is a better suggestion, please, let's suggest it to him!

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                  • #39
                    Originally posted by bstr View Post

                    SunEagle and Sensij, I'm only suggesting using excess production in a way that will benefit the owner more so than the 2.78 cents/kWh return. By the way, degradation studies show this is not a great concern and gas cars also lose efficiency. For this example, using a 3 year lease at a fixed cost with unlimited miles and 20 cents/kwh charging reimbursement (4.44 cents/mile actual) might show the return more clearly.

                    Driving 12,000 miles per year at 24 mpg (real world actual average when the sticker says 30 mpg) and $3.00 per gallon would cost $1,500
                    The Hyundai Ioniq has a 3 year lease for $275, call it $300 total, with unlimited miles. Driving it 12000 miles, you would get a credit of $533 per year (44/mo) in charging reimbursement. The more you drive, the more you get back, up to 50k miles.

                    So there you have it. That's my best suggestion for using the excess production for the most gain. If there is a better suggestion, please, let's suggest it to him!
                    Too funny... I just got in on the Ioniq in July (here is a thread). And, yes, I agree that it can be rational to find ways to consume excess energy, once the PV system is a sunk cost. Depending on what that cost was, though, the case that PV + Ioniq is a better financial choice than SDG&E + efficient ICE is harder to make.

                    (FWIW, I would gladly trade in my Spark EV for another Ioniq, even at double the monthly payment)
                    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                    • #40
                      Originally posted by sensij View Post
                      I doubt that focusing on super off peak rates specifically is any more or less accurate than any other estimate that might be used.
                      The reason super off peak is so relevant for EV owners with Solar systems is because on a TOU plan, half of production, generally speaking, is credited at peak rate. Using up the credit at super off peak times nets the user 2.5 times more energy using SDGE as an example (50 cents vs 20 cents in the spring/summer). The 3400 kWh of excess can easily equate to 24% more annually (4200 kWh), based on my own usage/production.

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                      • #41
                        Originally posted by sensij View Post

                        Too funny... I just got in on the Ioniq in July (here is a thread). And, yes, I agree that it can be rational to find ways to consume excess energy, once the PV system is a sunk cost. Depending on what that cost was, though, the case that PV + Ioniq is a better financial choice than SDG&E + efficient ICE is harder to make.

                        (FWIW, I would gladly trade in my Spark EV for another Ioniq, even at double the monthly payment)
                        That's great. I've had a Fit EV for 5 years, 82k miles and Kia Soul EV for 1.5. I wish the Ioniq deal had been around 1.5 years ago.
                        Last edited by bstr; 09-19-2017, 02:59 PM. Reason: *had

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                        • #42
                          Originally posted by bstr View Post

                          The reason super off peak is so relevant for EV owners with Solar systems is because on a TOU plan, half of production, generally speaking, is credited at peak rate. Using up the credit at super off peak times nets the user 2.5 times more energy using SDGE as an example (50 cents vs 20 cents in the spring/summer). The 3400 kWh of excess can easily equate to 24% more annually (4200 kWh), based on my own usage/production.
                          Oh, yeah, super off peak rates are a great deal for EV owners. I think SunEagle was saying that trying to project future electric rates for that TOU period would be more error-prone than other projections, but I'm not sure why that would be so. I haven't seen anything in CPUC proceedings that I follow to suggest the super-off peak pricing is at risk, and at least over a 5 year time horizon or so, would be reasonably confident in projecting the same kind of peak/super off-peak price ratio that we benefit from now.
                          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                          • #43
                            sensij , looks like you have some unscheduled maintenance coming up. This recall probably applies...

                            https://www.cars.com/articles/2017-h...1420697241176/

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                            • #44
                              Originally posted by sensij View Post

                              You would need to add in the cost of the EV itself (and insurance), or at least the difference relative to the most cost-effective ICE alternative, if you want to include gasoline offset in your return calculations.

                              I think that it is generally a losing game to try to justify an oversized array by intentionally shifting energy consumption from other sources to electricity. It may be appropriate given the sunk cost of the PV system, but you are more likely to be making lemonade than achieving the best case financial outcome that would have been available with a smaller PV expense.
                              Sizing a PV system to a load that may and most likely will change in the future is part of the application and a design parameter, but justifying the differential of the sunk cost that was made larger for vague or no reasons by finding uses for excess generation is inside out logic.

                              Whether or not (over)sizing for possible increased usage that may (or may not) occur at some time in the future is an application sensitive decision, and one that would seem to be at least partially at the mercy of the one picking up the tab for the PV system. Some would say that a signed contract for an EV is a pretty sure bet. Others might think a keeping up with the Jones' desire for an EV without some definite plans beyond "well, maybe in a couple of years, we'll see " might not qualify for laying out an extra $4K - $5K after tax credit array cost to save, say, maybe $750/yr. in differential fuel cost savings in fuel offset from 12,000 miles/yr. at 50 MPG for a Prius. Fewer people achieve than want. Plans and reality change.

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                              • #45
                                Originally posted by sensij View Post

                                I'm not sure where you are getting the idea that an EV becomes less efficient to drive over time. The battery capacity will fall, but if the car is properly maintained, the same 40 mi commute (for example) should consume the same amount of energy, and take the same amount of energy to recharge.

                                Some sort of estimation of what electricity rates will do over time is necessary for any financial justification of a PV system. I doubt that focusing on super off peak rates specifically is any more or less accurate than any other estimate that might be used.

                                Without doing any research, I'd guess that gas prices are more volatile than electricity, but there is probably a sufficiently conservative number that could be used to perform an estimate.

                                Vehicle depreciation can be a factor, but if the comparison is made on leasing costs (EV vs ICE), that can be a way to dodge that bullet, and conveniently sets the time period over which the analysis should be run.
                                I based my assumption that just about any battery takes more power to get it back to 100% as it degrades. That might not be true with the LI chemistry of the EV battery but I would think that older batteries not being able to get back to 100% SOC nameplate level makes the charger work harder therefore consumes more energy. I could be wrong in my assumption.

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