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  • Solar system happiness

    I have been a happy camper with my 11.47 kw system. So far the system is producing some great results since it went live November 15th, 2019.

    Nov 2019 total production was = 449.00 kWh
    Dec 2019 total production was = 698.20 kWh
    Jan 2020 total production was = 812.20 kWh
    Feb 2020 total production was = 951.20 kWh

    So far Mar 2020 production is = 964.20 kWh with 7 days left in the month the system has already surpassed the previous month.

    Some more data I've been keeping track of is daily production.
    Nov 2019 = 9 days of production over 30 kWh
    Dec 2019 = 3 days of production over 30 kWh
    Jan 2020 = 8 days of production over 30 kWh
    Feb 2020 = 17 days of production over 30 kWh = 5 days of production over 40 kWh

    So far Mar 2020 = 8 days of production over 30 kWh = 15 days of production over 40 kWh = 1 day of production over 50 kWh

    Needless to say the electric bill has dropped tremendously! I'm totally happy with my system and looking forward to tracking the production during daylight savings time.


  • #2
    Since your stated initial purpose for the PV was economic and I'm assuming that meant an initial goal of reducing electric bills with a longer term goal of economic breakeven calculated in some fashion for some point in the future:

    1.) Has your usage (gross, not net after deductions for PV production) increased or decreased since startup ? Many users notice an increase in use as the pressure from electric bills decrease.
    2.) What do you estimate your bills for the same periods you're reporting here would have been w/out the PV system?
    3.) What have your bills been for the same periods with the PV system?

    4.) What was the net cost of the PV system to you after tax credits/rebates ?
    5.) Have you estimated annual electric bill reduction due to the PV system's annual production ?

    FWIW, one parameter I've found interesting and also useful is a running 30 day total of array production. Also interesting, for me anyway, has been to compare that running 30 day total production with the PVWatts (and other models') estimate of production for the same running 30 day periods. For my system, and as an example only - your results will be different - after ~ 6 1/2 years of data, the modeled output from PVWatts for my system is pretty much within what the authors of the model claim for 30 day model to actual production variance. Also interesting - to me anyway - is that three other models I use show about the same variation and pattern(s) with respect to the ratio of modeled 30 day running output to actual 30 day running output.

    Comment


    • #3
      Sounds like your system is doing a good job.

      I guess my question is what is the yearly estimate savings in $$ and how long will it take to pay back the initial money you spent on your system?

      Comment


      • #4
        Always great when things go as planned! I used to "camp out" on my system data for the first few years but now only look at it once or twice a month. Our system has been live for over five years with the last three at zero net energy costs, I already know what to expect each month so it is a little more boring now.

        The install was designed to meet our needs near 100% and after the last kid moved out and we now over-produce and get a small account credit once a year. Payback fell from a predicted 7 years to just over 5 years after a series of fortunate events in cooperation with the local utility on several test programs for renewable energy customers. We pay $13 a month now and that is the minimum connection fee to have an active meter. Our agreement with the POCO is good for 14 more years so it might outlive me.
        Dave W. Gilbert AZ
        6.63kW grid-tie owner

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        • #5
          Hey guys thanks for reading about my excitement on the PV system. I will try to answer all your questions on this reply vs doing it one by one.

          Yes you are correct JPM my initial reason was to get my electric bills lower. So far that is certainly what is happening.

          JPM On the question of what my current bills are vs what they were last year same period, chart below shows a break down.
          Net cost for system after tax rebate and my initial contribution came to $31,352.00

          JPM I have not estimated an annual electric bill without PV and with PV system. Now with time off guess lol I will!

          SunEagle I have not done a cost per month cost comparison yet but I will. Especially since what my plans are to take those monthly savings and pay down the loan faster.
          My goal is to pay off the debt in 5 years if not in 4 yrs but I'm comfortable with 5 years. Sort of like a car payment.

          AzDave I know what you mean lol ! It sometimes takes me 5 days to input the numbers into a monthly spreadsheet. I'd like to keep track at least for the 1st - 3 yrs. Then I may get bored and go the same way as you. My system is expected offset 90% of our household usage. We seemed to have surpassed that and the system looks like it is over producing.

          [TABLE="border: 1, cellpadding: 3, width: 500"]
          [TR]
          [TD]Production 2019[/TD]
          [TD]2018 usage[/TD]
          [TD]2019 usage [/TD]
          [TD]2020 usage [/TD]
          [TD]Savings [/TD]
          [/TR]
          [TR]
          [TD]Nov - 449 kWh[/TD]
          [TD]1416kWh=$214.05 [/TD]
          [TD]450 kWh = $77.69[/TD]
          [TD]???[/TD]
          [TD]+$136.36[/TD]
          [/TR]
          [TR]
          [TD]Dec - 698 kWh[/TD]
          [TD]1355kWh=$206.16[/TD]
          [TD]562 kWh = $93.50[/TD]
          [TD]???[/TD]
          [TD]+$112.66[/TD]
          [/TR]
          [TR]
          [TD] [/TD]
          [TD] [/TD]
          [TD] [/TD]
          [TD] [/TD]
          [TD] [/TD]
          [/TR]
          [TR]
          [TD]Production2020[/TD]
          [TD] [/TD]
          [TD] [/TD]
          [TD] [/TD]
          [TD] [/TD]
          [/TR]
          [TR]
          [TD]Jan - 812 kWh[/TD]
          [TD]???[/TD]
          [TD]1011kWh=$152.37[/TD]
          [TD]133kWh=$28.12[/TD]
          [TD]+$124.25[/TD]
          [/TR]
          [TR]
          [TD]Feb - 951 kWh[/TD]
          [TD]???[/TD]
          [TD]1152kWh=$174.14[/TD]
          [TD]132kWh=$28.77[/TD]
          [TD]+$145.37[/TD]
          [/TR]
          [TR]
          [TD]Mar - 964 kWh[/TD]
          [TD]915 kWh=$134.93[/TD]
          [TD]946kWh=$144.52[/TD]
          [TD]??? [/TD]
          [TD]???[/TD]
          [/TR]
          [/TABLE]

          Since March 2020 bill has not generated I don't know the results yet.
          We are also experimenting with AC thermostat. We were keeping it at 78 degrees in 2018, 2019 but as of February 2020 we added more insulation. 78 degrees seemed to warm and the air felt stagnant. Now we are keeping it at 76 degrees. Trying to keep a balance for comfort. Lets see how the bill goes!



          Comment


          • #6
            Hmmm not sure what happened w the chart. What happened guys?

            Comment


            • #7
              Originally posted by juanj5678 View Post
              Hmmm not sure what happened w the chart. What happened guys?
              Sometimes the forum software will do some crazy things with your post. Depending on how you entered the info may depend on how it is shown.

              As for when you will pay back that $31352 may not be as soon as you think unless you are paying a very high electric rate even if you generate 11000kwh a year. At $0.25/kWh that comes to a savings of $2750 which will take over 11 years by my calculation.
              Last edited by SunEagle; 03-25-2020, 08:28 PM. Reason: added last sentence

              Comment


              • #8
                Originally posted by SunEagle View Post

                Sometimes the forum software will do some crazy things with your post. Depending on how you entered the info may depend on how it is shown.

                As for when you will pay back that $31352 may not be as soon as you think unless you are paying a very high electric rate even if you generate 11000kwh a year. At $0.25/kWh that comes to a savings of $2750 which will take over 11 years by my calculation.
                I'll have to look but how did you calculate 11 years.

                Thx
                SunEagle

                Comment


                • #9
                  Originally posted by juanj5678 View Post

                  I'll have to look but how did you calculate 11 years.

                  Thx
                  SunEagle
                  Well based on your first four months I first estimated you could generate about 11000kWh per year. It may be more or less but that was a starting point.

                  I then multiplied that 11000kWh by an estimated energy cost of $0.25/kWh which again may be more or less what your POCO charges you.

                  That calculated to $2750 per year (11000kWh x $0.25/kWh =$2750). I then divided that $2750 in your system cost of $31352 and calculated over 11 years.

                  These are just estimations concerning the amount of kWh you could generate and your $/kWh.

                  For me I get charged about $0.11/kWh which makes it very hard to get a payback less than 10 years unless I get a system installed for less than $2/watt. Yours calculated to about $2.74/watt ($31352 / 11470watts = $2.733/watt) which isn't bad but unless you are charged more than that $0.25/kWh your payback is not short.

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