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  • #31
    Originally posted by vtkahns View Post
    Just not something I want to do right now..
    This is kind of funny. To supply a device with stand alone battery will cost a minimum of $3000/kwh and require replacing the $700 battery every 5 years which means you will pay around $1.60/kwh with solar vs 14-cents from the power company. And you are complianing about buying a $1000 refrigerator that will save you 50% of your solar install. Try doing some simple economics. You can buy a new fridge plus a solar system to power it for less than a solar system to power what you have now.
    MSEE, PE

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    • #32
      Originally posted by Sunking View Post
      This is kind of funny. To supply a device with stand alone battery will cost a minimum of $3000/kwh and require replacing the $700 battery every 5 years which means you will pay around $1.60/kwh with solar vs 14-cents from the power company. And you are complianing about buying a $1000 refrigerator that will save you 50% of your solar install. Try doing some simple economics. You can buy a new fridge plus a solar system to power it for less than a solar system to power what you have now.
      I don't know what you are talking about with batteries and the like. I am not doing anything with batteries or off grid systems. I am installing a grid tied pv system and was just commenting on the usage of my 13 yr old fridge as being approx 2 kwh / day currently with my house at 58F .. and rated at 3 kwh/day per the sticker on it.

      If I pay $1000 to get this fridge and it saves me 50% or 500 kwh / year.. at the $0.14 it costs me to buy from the electric company.. that's a whopping $70 / year savings... I won't break even for 14 years.. I surely don't expect my current one to last 14 years so when it dies, I will replace it with an efficient one.

      Does that make sense now ?

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      • #33
        Originally posted by vtkahns View Post
        Does that make sense now ?
        Nope because if your current fridge uses 2 Kwh per day, and the new one uses 500 wh per day, you save 75% on solar installation. Rather than 500 watts of solar panels, it would take 125 watts to do the job.
        MSEE, PE

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        • #34
          Originally posted by Sunking View Post
          Nope because if your current fridge uses 2 Kwh per day, and the new one uses 500 wh per day, you save 75% on solar installation. Rather than 500 watts of solar panels, it would take 125 watts to do the job.
          I think I finally see what you are trying to get me to understand... I was not following at all until now.

          Net:
          current fridge/freezer rated 1000 kwh / year
          proposed new fridge/freezer rated at 500 kwh / year (probabaly more like 600 but we'll go with 500 for now )

          Delta = 500 khw *$0.14 = $70 less electricity used per year at my current going rate.

          However.. if I was trying to exactly match my electrical usage to the size of the system I am installing , I could install a smaller system, dropping say 2 panels. My estimate is this would save me $1252 for 2 , 245 watt panels after all rebates.

          Our power company buys back excess power at slightly less than the going rate ($0.13456) and pays cash for it.. not just credit on the bill.. So having excess, once I pay for the system, is more $$ i my pocket. The ROI for the system is the same regardless of size as its all based on the per installed watt price vs the price of electricity since they buy it all. They also pay a $0.06 premium on all power generated, regardless of usage.. Of course.. if they stop doing either of these, my ROI goes out the window and my system will be oversized for the task at hand.. probably 10-20% right now.. and more when the fridge is replaced.

          If there is an electric car in my future, i will need all of this excess power I would expect... so there is a bit of a gamble here but seems it will be a long time before those anywhere near roi.

          If I could drop the system size down at this point.. i could consider it but I think my installer would not be happy with me.

          This line of analysis I will admit I did not spend much time on up until this point.

          Thanks for continuing to drive the point until I got it.

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          • #35
            Originally posted by vtkahns View Post
            Thanks for continuing to drive the point until I got it.
            You are welcome, and I commend you on at least looking into ROI as most folks just go brain dead, all they hear is the hype and believe it. You just stop short and did not take everything into consideration to see the big picture.

            For most people solar cost them 3 to 6 times more for power than they pay now. Give you a good real life example. Joe homeowner pays $100 per month to the POCO for Power. Joe Homeowner buys a 6000 watt grid tied solar system to replace 100% of his electric usage. After rebates and incentives the system cost $30,000 and dumb ole Joe gets a 10 year loan at 7%. Now for th enext 10 years Joe Home Owner gets a $25 per month service charge from the POCO, plus $348 month payments. Joe Homeowner got what he asked for. Instead of paying $100 per month, he now pays $373 per month. Poor Joe if he had some basic math skills he could have invested $30,000 and it would have paid his electric bill each month, and in 10 years he would have doubled his money to retire on.
            MSEE, PE

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            • #36
              joe homeowner's roi

              So in my case.. approx $11K for 4.4kw system.. to produce say 5000 or more kwh / year where I live.

              $0.143 / kwh to buy from grid
              $0.13456 / kwh credited for net pushed back to grid
              $0.06 / kwh produced credited to each bill each month
              $11 / month or so service charge that will not go away

              My match came to 11.3 or so years to make 5000 * (0.0143 + 0.06) in electricty or $$ each year. Approx $1000 year generated.... to pay for the 11K expenditure.

              After 11 years, should everything be functioning, that $1000 is gravy.... Now.. had I invested the $11K into something.. and it doubled in 10 years... this is clearly not that type of investment.. I will take $11k.. throw it on the roof and reap a $1k dividend each year. 10% return... But.. the $11K eventually wears out and is worth nothing.. so the only real benefit is the electricty it produces..

              All i all.. its not going to make me rich.. but it is (a) doing the right thing and (b) not really any more $$ than paying the electric bill each month.

              Many ways to look at it...

              Hope it all works out..

              Comment


              • #37
                don't forget electric rates are *likely* to rise at some point in the future
                Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                solar: http://tinyurl.com/LMR-Solar
                gen: http://tinyurl.com/LMR-Lister

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                • #38
                  $ / kwh

                  Originally posted by Mike90250 View Post
                  don't forget electric rates are *likely* to rise at some point in the future

                  Oh indeed. I have an ROI case where I crank it up at the same rate that its gone up in 13 years since I have lived here.. approx $0.0032 / year. It turns 11.3 years into somewhere close to 10... and if it jumps up a nickel abruptly due to our nuclear plan being decommissioned in 2012 (one estimate I saw) , trims it to something like 8 years.

                  To me.. its close enough... If this took 20 years to pay for itself.. I would be much more hesitant.. getting it close to 10 years i would think would have people flocking to this. Of course.. we are pretty thrifty with our usage unlike others.. making the system up front cost to be near that 10K value. Someone that uses double what I use.. and has to fork over $20K up front, may get cold feet.

                  I hope if incentives vanish , that the prices come down enough to keep it near the same price point.

                  I have 2 neighbors that I am making my sales pitch to .. to try to get them on the band wagon.. One I think is very interested.. only problem.. the front of their house that faces the road and the whole neighborhood is facing south..

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