Comparing Geo to Solar PV

Discussion in 'General Discussions' started by Palace GeoThermal, Feb 19, 2011.

  1. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    I recently did a loop design on a 6 ton house.

    The loop software reported the
    Annual Ground Loop Load of 128,169,000 BTU's or 37,564 KW

    The cost of installing the 6 ton vertical loop will be $16,800.

    This got me thinking about how much it would cost to install solar panels capable of providing 37,564 KW per year.

    Any body here that can tell us what that solar system would cost?
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Welcome to my quest! lol

    I am trying to peel the layers back on these topics myself. I am trying to put a dollar amount for instalation of solar and or wind to get back x in generation. I am finding it very difficult to get data out of anyone.
    Let me know if you get any traction. I went to solar and wind on the other site and not much traction there. Curt gave me some good leads to chase but I am having time bugeting issues due to increase in work volume that pays curent electric bill or invests in windmill. Viscious circle?
  3. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    I assume you mean 37,564 KWH / annually? If so, it would cost 10-13 times more than your vertical loop. Of course, that is before any incentives.
  4. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    Yes, I have yet to find and/or join a solar/wind forum that is as much value as this forum is. I love solar and have it also on my home! I have completed some unique solar projects, all in the residential market. Feel free to contact me!
  5. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Thanks for the info.

    So in terms of energy provided versus capital costs, would it accurate to say you get about 10 times more bang for your buck from geo than solar?

    What would the combined size of the solar panels be?
    Last edited: Feb 19, 2011
  6. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    In my kneck of the woods wind seems to be the best choice? The best site I have been on so far is . In less than 5 minutes I had a lot of info including lat&long for my house, google earth with interactive to place wind mill. By supplying them with average kwh per month and size of windmill they provided an estimate of 60% reduction per year in electric usage. Then the dreaded " a sales rep will contact you soon with pricing". At least I am making progress in regard to "what will I pay for a 60% reduction in consumption"
  7. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    So I found this Solar Package that costs $50,820.

    I really know nothing about solar systems.

    The package is rated at 7260 watts. Does this mean that the solar panels will provide 7260 watts when the sun is shining at the optimal angle?

    How would I know how many watts it would produce in a year?
  8. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Change the watts to BTUs.

    Or I would look at solar thermal. Caleffi's web site will give you access to Idronics issue #3. It is a free download which can be used to figure your solar fraction. I do not have the link in this new laptop. They have a 3 panel kit that retailed for about $20,000 a few years ago. I am sure if you asked they would give you current numbers.

    I am a certified installer, but have yet to sell a $12,000 DHW system which is what they thought was there market. If you need or want more let me know..

  9. ChrisJ

    ChrisJ Active Member Forum Leader

    Solar cost

    I spoke with a rep here in RI, wanted a price on a system that would produce 7500KWH per year(approximate 50% of my usage). He said about 36K turn key. Before tax break.
  10. Looby

    Looby Member Forum Leader

    Don't know 'bout the panels, but the supplied inverter (SB7000US)
    is rated 7 kW maximum (actually, 29A @ 240V, 60Hz = 6.96 kW).

    So, no matter what the sun intensity or angle, the output is < 7 kW.
  11. Texas Cooler

    Texas Cooler New Member

    Using SLC for average insolation, 7.260kW * 5.3 hours/ day = 38.478 Kwh/day avg. * 365 days/yr. = 14044.47 kWh/yr. gross production. The 5.3 hours/day is for a fixed array at SLC latitude.

    Using an average of .77 factor to account for wiring losses, inverter losses, dirt on panels, etc = 10814.241 net Kwh/yr. avg.

    Depending upon the supplier and brand of panel, I have seen panel pricing <$3.00 watt. Of course you need the inverter and all the other little "nuts and bolts" plus labor to install.
  12. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Chris, any idea what the square footage of the panels would be that you were quoted?
  13. ChrisJ

    ChrisJ Active Member Forum Leader

    I left my notes at the shop. We talked about possibly having to ground mount. I think it would fill my 64'x30' ranch roof which faces SSW.
  14. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Good details in Tex's post. Start with the system's peak output, multiply that by average hours of solar insolation and then by a factor considering all the losses.I think I've seen factors in the 0.7 range in Homepower magazine, but those systems may have had batteries, further reducing efficiency.

    The panels can be had at $2.50-$3.00 per Watt lately, but balance of system costs more than double the panel cost.
  15. sunnyflies

    sunnyflies Member Forum Leader

    Maybe this will help, it came from an email from the solar installer I used last year: "To determine system size vs customer usage, we use a factor of 1.275 per 10kW. This say's that under standard test conditions, a 10kW system will generate 12,750kWh annual. "

    And, this is from their bid. You will have to separate the three ROI scenarios at the end as the computer keeps running them together no matter what I do:

    System Size: 6,300 Watts
    Retail Cost of System $44,100

    LIPA Rebate (3.50) $ /Watt (22,050)

    Net Retail Cost $22,050

    % Cap
    NYS Tax Credit -25% ($5,000)

    Fed Tax Credit -30% ($6,615)

    Net System Cost after Rebate & Credit $10,435

    Estimated Savings & Return on Investment:

    Electricity Produced 127.5%kWh/W/Yr 8,033 kWh/Yr

    Loss factor for orientation, pitch & shade -14.6%***

    Net Energy Produced 6,863 kWh/Yr

    Lifetime Energy Produced 188,278 kWhs****

    Net Cost of Solar Power $ 0.055 /kWh

    Current Cost of LIPA Power 0.208 /kWh

    Scenario 1 Scenario 2 Scenario 3
    Ave. Annual Increase In LIPA Electric Cost 5.0% 7.5% 10.0%

    Estimated Useful Life 30

    Estimated Lifetime Electric Savings $84,818 Savings $130,746 Savings $206,292

    Lifetime Return on Investment 813% 1253% 1977%

    Ave. Annual Return on Investment 18% 20% 23%

    System Pays for Itself After Years 6 6 5
    Last edited: Feb 20, 2011
  16. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Thanks for all of the info. I am going to produce a marketing tool that will show how geo compares to solar.
  17. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Now THAT is a special case

    LIPA power costs 20 cents per kwh - now I see why - they are willing to pay almost half the gross price of a PV system

    The the feds and state pick up more than half of the remaining half. Homeowner gets a PV system for 25 cents on the dollar in one of the highest cost utility areas in the country.

  18. sunnyflies

    sunnyflies Member Forum Leader

    Well actually, we had to pay for half the cost of the solar voltaic system - not a quarter of it, though after tax credits a year later it does drop the cost down quite a bit. It cost us $22,000 out of pocket, but luckily we did get both state and federal tax credits which helped to off set the cost, much like the tax credit we got for our geothermal system.

    LIPA doesn't offer solar rebate money out of the goodness of its little black heart, or even out of the high rates it charges. It has some federal grant money which it uses to offer rebates to "solar pioneers" and I know is looking for more. Unfortunately, it keeps lowering the amount it offers, to spread it farther I think. Friends who got their system several years ago paid far less than we did as the rebates were fabulous back then, about $5 a kw instead of $.3.50.

    We are extending our solar panel system shortly, but will be paying proportionally more than what we paid last June because LIPA reduced its rebate yet again, to about $2.75 I think, alas. :(
    Last edited: Feb 21, 2011
  19. jml

    jml New Member

    The amount of annual kWh generated by an installation of a specified kw of panels varies with locale, weather, panel azimuth and tilt, and other installation factors. The online PVWatts calculator is a simple and fairly accurate tool for determining how much energy will be produced by a proposed install: PVWATTS v. 1

    PV panel prices are trending down to under $2.00 per watt....for example, take a look at this price survey here: Solar Panels Price Survey - Lowest Solar Panel Prices (although note from the fine print on this site that it is not really just an unbiased survey).

    When you add the cost of racking, inverters, permits, wiring, and installation, you can easily be in the $6.00 per watt range. A lot of the install work can be DIY-able...but this is dependent on your local rules, which can vary a lot. The gov't incentives and utility rates for net-metering or feed-in-tarrifs also vary a lot from place to place...which is likely the biggest influence on whether geo or solar pv provides the best bang for the buck.

    The best forum I've found for solar is: Solar Electric Power Discussion Forum by Northern Arizona Wind & Sun
    (although a lot of the discussion is around off-grid solar, which is a whole different ball game than grid-tied)
  20. ClarkT

    ClarkT Member

    From some seminars/trainings we've attended, $6.00-$7.00 per Watt has been the approximate guess of PV installed.

    This is definitely an interesting comparison to make. I can envision quite a few different ways of putting it, too.

    For your $16,800 price on the 6 tons, is that just for the ground loop? Just want to be clear we're comparing the right thing...and, that's a drilled loop, right? If it's drilling, how many feet per ton is that one? just curious.

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