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Solar power almost unviable / not worth it?

Post in 'DIY and General non-hearth advice' started by TheMightyMoe, Aug 31, 2012.

  1. TheMightyMoe

    TheMightyMoe Minister of Fire

    Joined:
    Aug 2, 2012
    Messages:
    543
    Loc:
    Fairbanks, Alaska.
    Called local place, didnt like his opinion on solar power (Bias).
    Went online did a lot of homework, think I have it about figured out.

    At current usage.

    27.7KW per day
    1.15 KW per hour

    So if we want to run 100% solar 8 monthes out of the year we get 10 hours a day. ((Assuming panels get all that light)
    So an excess of 14 hours is required or 16.1 KW (16.1 / 10 = 1.61 KW needed in excess a hour)
    So in total we need 2.76 KW per hour of sun or 14 panels
    Panels are 250w for 400$ (Counting them as 200 because your never suppose to expect 100%)
    Batteries are 12vh 125ah for 250$

    5600$ in panels and at least 12 hours of battery life or 12/1.5= 8 batteries or 12,000 watts.
    2000$ batteries
    400$ inverter setup
    400$ charger setup
    Material 500$ (Ball park)
    8,900$

    This will save us 200$ month in electrical at current rates for 8 monthes so it will save around 1,600$ yearly.

    A 5.5625 year turn around.

    You will need 2000$ in batteries every 8 years.
    So in a 20 (Panel "life") year run period you will spend $15,100 but save 32,000$ a overall savings of $16900.

    5600$ panels
    5000$ batteries (Assuming 2.5 replacements)
    2000$ inverters (Assuming 4 replacements)
    2000$ chargers (Assuming 4 replacements)
    500$ materials

    So you save approximently 845$ a year or 70$ a month for 20 years. Including the 4 winter off monthes worth of sunshine it came out to about 9$ extra a month saved.

    If anyone is good at solar/electrical your opinion would be appreciated. Please keep this far from political, this is about saving $$$.

    I think I am pretty much going to get a couple panel setup just for summer, and see how much I can I pull/save with our 20 hour days, I just can't justify the upfront cost to save so little a month.

    -Moe

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  2. seige101

    seige101 Minister of Fire

    Joined:
    Mar 25, 2008
    Messages:
    530
    Loc:
    Palmer, MA
    Ditch the batteries and use the grid as your battery. If you have un-used power being produced during the day it makes the meter run backwards. When you are using more power thank your are producing or the sun is not out the meter will run as normal. This will save you some significant costs.

    However based on your above math of a $8900 investment and a return on it in 5.5625 years, that seems like a no brainer to me. Where else can you get that current return on investment?

    What if you took that $200 a month savings and used it to pay down your mortgage faster? How much would you save in interest?
  3. woodgeek

    woodgeek Minister of Fire

    Joined:
    Jan 27, 2008
    Messages:
    2,614
    Loc:
    SE PA
    Sounds like you are on the right track....there are lots of good resources out there. Google PVWatts to figure out how much solar you should expect.

    What is missing....

    What is your price per kWh? IF high, then the payback looks better.
    Why use batteries if you can do grid-tie...is such available in Alaska? If so, the upfront is lower and the payback better.
    If you go the off-grid route, it will roughly double your cost per solar kWh, and you will need to keep the batteries vented to the outside and protect them from freezing.
    Most folks that go off-grid really minimize their electrical loads...27 kWh/day seems a bit high....can you shed some load before you start??

    Ok, I looked at PVWatts, and it looks like a 1kW nominal panel that gives 770W AC under full sun, will yield ~900 kWh (AC) per year in Fairbanks (assuming a fixed panel tilted at your latitude). Not surprisingly, only 1% of that is in December.

    You seem to be assuming 2400 hours/year at 80% of nominal output, or 1900 hours at 100% equivalent. Weather data seems to suggest a 'harvest' a bit less than **half** of that. My guess is you are missing the loss of power that occurs when the sun is not perpendicular to the panel. That factor is about 50% on an average basis. A Tracking array (which would likely require a ground mount) would remove this problem.
  4. TheMightyMoe

    TheMightyMoe Minister of Fire

    Joined:
    Aug 2, 2012
    Messages:
    543
    Loc:
    Fairbanks, Alaska.
    .22$ / kWh.

    I will research grid tie.

    Yes you are right about the loss of power.

    I will check out PVWatts.

    Thanks!
  5. xman23

    xman23 Minister of Fire

    Joined:
    Oct 7, 2008
    Messages:
    778
    Loc:
    Lackawaxen PA
    My understanding is the power co will only buy your power if they need it to meet there mandaed amount of renewable power.
  6. Jags

    Jags Moderate Moderator Staff Member

    Joined:
    Aug 2, 2006
    Messages:
    14,901
    Loc:
    Northern IL
    Some places actually "require" them to buy back anything that is overproduced.

    It is a pretty well known fact that when it comes to electricity - your best bang for the buck is finding out how to reduce the usage. Plain and simple.
  7. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Feb 14, 2007
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    27,816
    Loc:
    Michigan
    If you do go the battery route, we found 6 volt deep cell batteries (golf cart batteries) are much better than the 12 volt deep cell. Cost, last time we checked was not that much more and they lasted longer too.

    If going solar, it definitely pays big time to have them follow the sun and I would think doubly so in your area. We used to winter in Arizona and during the months of December through February we changed the angle. Sometime in early March we could stop and just leave them down. During those winter months it made a huge difference in output from the solar panels. We had 4 panels and most of the time we did not have to use the generator at all.

    I thought all electric companies were required to buy the electric but not sure on that.
  8. greg13

    greg13 Feeling the Heat

    Joined:
    Jan 5, 2012
    Messages:
    446
    Loc:
    CNY
    WAIT!!!! You forgot to factor in the Federal & State grants to purchase the equipment. When you factor those in, your out of pocket costs drop by 75% at least. Only in America!!
  9. xman23

    xman23 Minister of Fire

    Joined:
    Oct 7, 2008
    Messages:
    778
    Loc:
    Lackawaxen PA
    I thought all electric companies were required to buy the electric but not sure on that.

    What I have found out about rebate programs is it's a moveing target, state by state that come and go. Pay back from the power co is equally hit and miss. I know a situition where the gave up trying to collect from the power co. They now use all there extra power as heat in the winter. There are some very knowledgeable people on "the green room" that can better comment on this.
  10. Thomas Anderson

    Thomas Anderson Member

    Joined:
    Sep 3, 2012
    Messages:
    149
    Loc:
    Central PA
    Apparently my original reply in here was deleted. I'm not going to repeat the whole thing. But the gist of it is, you need to get your demand to under 10 kWh/day before you think about solar being worthwhile for you. And if your goal is to save money over the grid, then your base assumption is that grid power is going to get much more expensive over the life of your solar panels. If you do not hold that assumption, then there's no point in buying solar for saving money. There are many very good reasons for getting solar and going off-grid, but merely saving money is not one of them. You can find my fairly comprehensive list of motivations for going off-grid at my site: http://andersonalternative.com/, where I posted a power point presentation that I give at my university.
  11. nate379

    nate379 Guest

    Not sure how you guys do it up there for juice, but here with MEA they buy back the power. It's on a credit program. Get a special meter with 2 dials. At the end of the month they figure how much juice you made vs what you used. If you made more, you get credits. The credits gets used on months that you made less than used (winter). At the end of the year they cut you a check if you have extra credits left.

    I have 16 panels on my roof, 4000 Watt system.
    Canadian Solar panels with Enphase inverters. Grid tied, no batteries.

    I needed 24 panels to cover my power use 100%, but only had room for 16 on the building I put them on. Panels are about 3.5x5ft

    I have not put it online yet, I just got the panels up about a month ago and I haven't had time to finish wiring it to the panel. (Trying to get outside stuff before it snows!)

    My numbers worked out that it will pay itself off in about 7 years. The panels have a 25 year warranty.


    Keep in mind too there is a 30% gov rebate for solar panels on the income tax.


    Does not pay to have them motorized for a large system. The racking and controls to do that are $$ and fairly complicated. With the snow and winds we get, they don't hold up. Couple panels mounted on a pole different animal.

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