Actual, real life solar numbers

Discussion in 'Off Grid Living' started by TnAndy, Jan 27, 2011.


  1. TnAndy

    TnAndy Senior Member Founding Member

    I posted this over in another forum, and thought some of you folks considering solar might be interested in some real life number versus theory.

    My system is: 3150w panel rated. 18 x 175w Solarworld panels. 2 FM60 charge controllers, a 1200amp/hr AGM battery bank, 2 GTFX2524 inverters ( 2500w@24v). This system is grid tied in normal mode, and switched to off grid when the grid is down ( the GTFX inverter has an extra contact that closes when the grid contract opens on grid down, and diverts power to where ever you have it wired to go.....transfer switch in my case )
    The panels are mounted on two sets of home built single axis trackers. These help the panels produce about 20-25% more power over the course of time than fixed mount, based on what I have measured by turning off the trackers and leaving them in the 'noon' position. The horizon angle of the trackers is fixed at 37 degrees, my latitude.


    Here are the production numbers for 2010:

    Solar Kw/hr......Total Kw/hr used....$$

    Jan---212...........1200...............55.07

    Feb--149.............1854..............121.04

    Mar--168.............2092..............141.92

    Apr--203..............1813..............118.72

    May--295..............865................<0.26>

    Jun--346...............679.................<4.20>

    Jul--296................847..................22.20

    Aug--366...............1132.................34.05

    Sep--291................985..................37.59

    Oct--407.................855...................4.03

    Nov--339................757......................7.54

    Dec--267.................664..................13.14

    Total for year 2010: 3339 solar produced
    Average per month: 278.25kw/hrs produced

    Total used for 2010: 13,743
    Average month: 1145kw/hrs

    Total electric bills: $550.87
    Average monthly bill: $45.91


    NOTES:

    1. This is my house, and my woodworking shop, and several farm buildings/etc. Some months I will run my dry kiln in the shop, and run the Kw/hrs up 200-300 for a month. It also depends on the amount of time I spend in the shop, several motors are 5hp on various machines, and the dust blower which runs with most machines is 3hp.

    2. Also, we run stock tank heaters and chicken house heat in the winter, which tends to run the use up out of proportion to the year.

    3. Being September, we switched to propane gas stove in the new kitchen, which will affect use some. Also switched to LED lighting in a major way.

    4. We will run electric AC some in the summer, mostly July/August.

    5. We get paid 12 cents OVER retail for all solar production ( TVA 10 yr contract ) Retail varies around 9 cents/kw/hr, depending on quarterly fuel adjustment. Amounts in <> reflect credit amount in our favor.




    System cost about 20k, self installed.

    Future expansion will be to add another 2450w of panels and one more charge controller ( FM80 ) to the system. That will max out what the two inverters will feed back to the grid ( they loaf along now at about 2.3-2.4kw best case ), and that will maximize all the equipment I have.
     
    grunt351, VisuTrac and hank2222 like this.
  2. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Hm. I average around 550kw per month which means I could use your set up to go completely off grid. Close to average, my bill is 60 FRNS per month. So, using your 20K sunk costs, I'd get payback in, say, 7 years, neglecting any maintenance, and ignoring my higher latitude and winter cloud cover.

    It's worth considering that doing the install myself is problematic, thus added costs. And, cloud cover here is not trivial, there have been about 10 sunny days since the beginning of December. Cover alone would require an alternate source and extend payback by roughly 30%. Looking very carefully at actuarial data, there's a better than even chance I won't live long enough to see the benefits other than not having a 60 FRN outgo every month for most of the year.

    Heh. Not sending money to Penelec would be a neat thing, but the economics don't work for me. I'm rolling the dice, I know, but all of life is a gamble, and prepping falls into the same category, you have to decide where the risks are greatest and prep for them.

    Andy, I fully respect your ability and energy, and envy your position. You are doing SM a real service with data to base decisions. Thanx.
     
  3. TnAndy

    TnAndy Senior Member Founding Member

    You're welcome.....

    but check the numbers again....my average production per month is 278kw/hrs. You would need TWICE my system ( in my location ) to replace 550/mo.
     
  4. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Where, oh where, is the Fountain of Youth? (y)
     
  5. TnAndy

    TnAndy Senior Member Founding Member

    Dunno....but if you find it, bottle me up some. The aniversery of my 6th decade is right around the corner.
     
  6. Nadja

    Nadja RIP 3-11-2013 Forum Leader


    Already been there and am now beyond !
     
  7. TnAndy

    TnAndy Senior Member Founding Member

    Yeah, thought you seemed like an old(er) fart. :D

    Remember when we were young men...it was about whose was longer. NOW, it's about who outlives who......ahahahaaaaa.......

    Meter reader was just here at lunch time, I have the numbers for what will be the Feb/11 bill. ( from 12/23/10 to 1/27/11.....which is 35 days, compared to last year's Feb, which was 30 days, 12/28 to 1/27)...billing period use runs about month behind actual billing date.

    Last year: Solar produced = 149
    This year: 339

    Total Kw/hr used last year: 1854
    This year: 1280...AND is was 5 days more !

    So, we have cut down compared to last yr, based on a small snapshot.
     
  8. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Hi Andy, let us never forget to respect our elders . LOL Glad you are keeping track. Heck, I don't have anything to compare to as have never been on the grid since we bought this land years ago. Or was that centuries ago !
     
  9. fireplaceguy

    fireplaceguy Monkey+

    It was last century, at the least...
     
  10. timtebow970

    timtebow970 Monkey+

    this is the type of information I have been looking for. Thank you TnAndy for the info and thank you Nadja for asking me to join this forum.
     
  11. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Timetobow, your welcome, Andy, mine is bigger then yours. Your such a youngster still , that i'll bet you can't pixx. straight yet ! LOL Grit, you would need a lot more solar if your up there in the nw part of the country. Here your getting another storm incoming about now ? Hunker down
     
  12. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Sunlight has been really hard to see the last couple months, that's for sure. Right now, we are in a thaw cycle, hasn't been below freezing for 2 days. That's supposed to change come the weekend.
     
  13. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Sure looks to be going cold and wet again. Same here, but not to sure just how bad. Right now, my solar panels are all smiling. Hope they stay that way !
     
  14. TnAndy

    TnAndy Senior Member Founding Member

    April has been a pretty good month, and today was a REAL solar day....that deep blue, clear sky. Did 19kw/hrs today, which is about as good as our current system does. For the month, we've bought 227 kw/hrs and produced 414, for a total use of 642.
     
  15. thebastidge

    thebastidge Monkey+

    On the plus side, in the higher latititudes our solar panels would be mounted at a higher angle to let snow slide off more easily... ;)
     
  16. VisuTrac

    VisuTrac Ваша мать носит военные ботинки Site Supporter+++

    I think it's beer.

    [​IMG]

    TnAndy. How do the AGM's compare to the Lead acid batteries on longevity/maint/cost? Just curious.
     
    hank2222 likes this.
  17. TnAndy

    TnAndy Senior Member Founding Member

    Higher cost ( except I got these realllllllllly cheap ), no maintenance, and these are supposed to be a 20 life battery.....that of course, would depend on the number of times cycled and depth of discharge......the 20 year rating assumes them kept basically topped off and only for occasional use.
     
  18. TXKajun

    TXKajun Monkey+++

  19. TnAndy

    TnAndy Senior Member Founding Member

    The answer lies in one of the comments posted in response to the article:

    Sky King said:

    Looks like, that those with home solar panels should TURN OFF the incoming electric meter when they are producing enough for themselves.
    And then, when they need more power from EPEC, turn the incoming power/meter back on.
    Use your own solar power for yourselves and dont worry about selling anything to EPEC.
    IF you need more power then turn the EPEC meter back on.
    Right now, it looks like, the solar producer is selling ALL of their power, at wholesale, to EPEC and then BUYING it BACK at retail.
    That makes no sense.

    You need a switch that only turns on the power from EPEC, only when you need it.
    Otherwise, just use your own solar power.


    This would have the effect of getting retail rate, a 'penny saved being a penny earned'.

    We had something similar here when I first signed up to sell back to TVA. They claimed to pay 15 cents/hr for all solar power......which they did....recorded thru a separate meter.

    BUT what they also did was turn around and charge you 9 cents/hr ( retail ) for that same power....so in effect, you were only getting 6 cents/hr net.....less than retail by 3 cents. I was going to simply have them remove the "buy" meter from my place and run my solar directly. The only way you actually got 15c/hr was IF you produced more than you consumed in a month....and for most folks with a small to medium sized system that was NEVER gonna happen.

    Once I figured out what they were actually doing ( and believe me, THEY didn't understand it either.....we had many arguments back and forth with various officials ), I figured anyone with less than an 8 to 10kw system was better off to get off their "buyback" program.

    THEN, they decided to change to the way they paid, and now we get 12c/hr over retail, and it floats with retail, versus the old 15c rate that was fixed. Now we get an honest 12cents, and if you happen to produce more than you use, you get 12c + retail. When I put up my next set of panels, I will be doing that to the tune of them owing me about 30-50 bucks/mo.

    I don't think when TVA set up the original buyback program they REALLY understood the economics of it.....they thought they were actually encouraging solar/wind....it took some people actually setting up systems and examining the rate structure to point out the folly of it....and once they did, they changed the rate structure.

    That may, or may not, be the case in Texas......but either way, it seems a homeowner could simply replace what they would normally buy from the power company with their own source, and "get paid" full retail by NOT buying that much from the power company. What they would have to do is size their system so as not to produce more than they consume, and change some of their consumption habits to where they used more during daylight hours ( say, run a clothes dryer, for example, at noon rather than at night ) so nothing fed back to the grid to be paid wholesale.
     
    hank2222 likes this.
  20. hank2222

    hank2222 Monkey++

    In my area of Az it was going to be about $15,000 dollars or more to run a simple power line out to my place at time when we where looking to live there full time. so that why i chose to be totaly off grid out there .
     
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