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Thread: Solar power question

  1. #1

    Solar power question

    Hypothetically, if one were to install solar panels on the roof of an 8' x 8' storage shed, how much electric would that produce, using the whole roof as 2 giant solar panels ???

  2. #2
    Join Date
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    Orientation of the panels, and panel efficiency matter.

    More important, how far North do you live?
    The amount of sunlight falling on the panel is the primary factor.

    http://www.wunderground.com/calculators/solar.html
    http://www.solarreviews.com/solar-in...er-calculator/
    Last edited by Jim Matthews; 11-11-2014 at 9:19 PM.

  3. #3
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    Too many variables for an accurate diffinitive answer. Location, time of day, season, and orientation of the panels to name only a few. The brighter the sunlight, and the more directly it hits the panels, the more they produce. The panels don't normally lay flat on the roof, and all are usually mounted on brackets facing them due South, at varying inclinations, depending on your latitude. But to give you a rough idea, during optimum conditions, 400 square feet of PV would produce roughly around 5000 Watts. Some of the smaller panels in the 20 square feet range, produce around 240 Watts maximum. The better systems will charge a bank of batteries, and utilize inverters to convert the direct current power into alternating current.
    Last edited by Matt Marsh; 11-12-2014 at 8:26 AM.

  4. #4
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    Our utility company was happy to hook us up with an outfit that came out, did a site survey, and provided several options for panel configurations, financing options, and energy production and payback calculations at no cost. Try giving yours a call.

    Our system now makes about 40% of the power we consume and is on track to pay back in ~6 years, about a year sooner than their estimate--maybe sooner, since our local electric company just got approval for a 27% rate increase.

  5. #5
    Im assuming your talking about a gable roof and using both sides of the roof (covering the entire roof with panels). This wont be worthwhile as depending on orientation of the building one side will make virtually nothing and the other may or may not be facing/sloped adequately either. That said, in about 64 square feet (8x8) one may get about 800-1000 watts of panels in that area. That number is the peak output of the array as well so your total daily/weekly production will vary based on your location.

    Its no a big array for the investment.

    I have an off grid home with a modest PV system (about 1400 watts of PV). Its not an economically viable option for power unless you have substantial other factors impacting the cost of your power, getting power, or some government subsidies to offset your installation cost.

  6. #6
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    A word of caution regarding solar regulations. The rules can change, and that can add years to pay back calculations.

    In Arizona APS is one of the big utilities involved with solar. They are now angling for:

    -Requiring that solar panels be located facing west. Why you ask? "Because peak energy requirements are in the late afternoon". I wonder who that change would benefit??

    -Elimination of Net Energy Metering.

    Perhaps this type of irrationality is unique to APS. Any thoughts?

  7. #7
    I think your going to see more and more utilities start to try to un-do net metering agreements and they will more than likely curtail their future agreements. My state has never, and likely will never, have a lucrative net metering agreement (unless they are forced) due to energy interests here.

  8. #8
    Quote Originally Posted by Mark Bolton View Post
    I think your going to see more and more utilities start to try to un-do net metering agreements and they will more than likely curtail their future agreements. My state has never, and likely will never, have a lucrative net metering agreement (unless they are forced) due to energy interests here.
    Net energy metering is being required as a way to encourage people to install solar. But it really isn't fair. Those of us who have solar provide electricity to the power company during the periods of highest usage (middle of the day). But in the evening, we have to draw power from the grid.

    I have solar on my home, and I generate enough power that I don't have an electric bill. But I use the grid - I depend on the grid. If it wasn't for the grid, I'd be without electricity for a major part of the day. But I don't pay a penny to support the grid.

    As more people go solar, like me, the power company has to increase rates for the people who don't have solar, and that increase in rates encourages more people to install solar.

    There has to be a fair charge for people with solar systems for their use of the grid.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  9. #9
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    Quote Originally Posted by Mike Henderson View Post
    Net energy metering is being required as a way to encourage people to install solar. But it really isn't fair. Those of us who have solar provide electricity to the power company during the periods of highest usage (middle of the day). But in the evening, we have to draw power from the grid.

    I have solar on my home, and I generate enough power that I don't have an electric bill. But I use the grid - I depend on the grid. If it wasn't for the grid, I'd be without electricity for a major part of the day. But I don't pay a penny to support the grid.

    As more people go solar, like me, the power company has to increase rates for the people who don't have solar, and that increase in rates encourages more people to install solar.

    There has to be a fair charge for people with solar systems for their use of the grid.

    Mike
    +1. But many people don't see it that way!

  10. #10
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    With increased local generation to meet local peak demand there is need for much less "grid", which utility companies don't like because it decreases their rate base. However it's very good for the rest of us. During the day the power generated on my roof stays in the immediate community, powering a couple houses to each side of me, the POCO investment to distribute it is minimal. The utility company is also able to take advantage of my capital investment in generation capacity for free; its as if I've made them a free loan to build generation capacity. I'm not sobbing any big tears for them; their executives are richly compensated and their share/bondholders aren't doing badly either. As the need for expanding distribution grid and centralized generation declines even the other ratepayers should also see financial benefit. This conversion is, for now, helped substantially by public subsidies but that situation will change with scale and cost efficiencies and we will all be better for having made the investment in conversion-- just as electrification of the country in the early 20th century benefited from large public investment and yielded substantial public benefit, so too will this.

  11. #11
    Quote Originally Posted by Mike Henderson View Post
    Net energy metering is being required as a way to encourage people to install solar. But it really isn't fair. Those of us who have solar provide electricity to the power company during the periods of highest usage (middle of the day). But in the evening, we have to draw power from the grid.

    I have solar on my home, and I generate enough power that I don't have an electric bill. But I use the grid - I depend on the grid. If it wasn't for the grid, I'd be without electricity for a major part of the day. But I don't pay a penny to support the grid.

    As more people go solar, like me, the power company has to increase rates for the people who don't have solar, and that increase in rates encourages more people to install solar.

    There has to be a fair charge for people with solar systems for their use of the grid.

    Mike
    I couldnt agree more. I think the very early 1:1 net metering agreements by some utilities were very short sighted. There is no way they can pay you the exact KWH for energy delivered back to them as they charge you for energy you deliver over your short lines. You have no transformer and line costs, transmission and regulatory costs, on and on. But the simple fact of the matter is many power companies are wanting to get to a zero return situation (which is where I think this will eventualy go) where you will have panels on your roof and you will still pay a monthly bill and a substantial one at that.

    States (mine included) have proposed and opted for a zero return net metering agreement. This is where you feed all you want back to the grid and get little to no return for it. That is to say you can offset your electric bill to zero but it will never go beyond that. Getting to zero is infact possible for a conserving household. It will never happen for the average US consumer but it is possible.

    To me it becomes a philosophical issue. I understand full well I shouldnt be credited my KWh rate on my bill but there should be something there. The utilities will most definitely get their way though and you will wind up paying to generate power for them.

  12. #12
    Quote Originally Posted by roger wiegand View Post
    With increased local generation to meet local peak demand there is need for much less "grid", which utility companies don't like because it decreases their rate base.
    The rate base has nothing to do with the grid. The rate base is the number of customers and the amount of electricity they use. More or less grid doesn't affect how many rate paying customers the company has.


    Quote Originally Posted by roger wiegand View Post
    During the day the power generated on my roof stays in the immediate community, powering a couple houses to each side of me, the POCO investment to distribute it is minimal.
    True, but at night, or during periods of overcast, you need the grid. And your neighbors need the grid. The power company has to have generation and transmission capability to handle the maximum load, or you have to tolerate rolling blackouts. The grid is critical to people who have solar systems, unless they completely disconnect from the grid.

    Quote Originally Posted by roger wiegand View Post
    The utility company is also able to take advantage of my capital investment in generation capacity for free; its as if I've made them a free loan to build generation capacity.
    There's no way to have a sustainable business if you have to pay the same price for your electricity as you get when you sell it. Your argument would be valid if you sold your electricity to the power company at the price they pay the commercial generators, but not if you're selling it to them at retail prices.

    The grid will not - and can not - go away if you want reliable electric service. It provides a critical service to you and it has to be paid for and maintained. If you think it has no value, try doing without it.

    Mike
    Last edited by Mike Henderson; 11-12-2014 at 7:55 PM.
    Go into the world and do well. But more importantly, go into the world and do good.

  13. #13
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    Quote Originally Posted by Mike Henderson View Post
    Net energy metering is being required as a way to encourage people to install solar. But it really isn't fair. Those of us who have solar provide electricity to the power company during the periods of highest usage (middle of the day). But in the evening, we have to draw power from the grid.

    I have solar on my home, and I generate enough power that I don't have an electric bill. But I use the grid - I depend on the grid. If it wasn't for the grid, I'd be without electricity for a major part of the day. But I don't pay a penny to support the grid.

    As more people go solar, like me, the power company has to increase rates for the people who don't have solar, and that increase in rates encourages more people to install solar.

    There has to be a fair charge for people with solar systems for their use of the grid.

    Mike
    I really appreciate that honest and enlightening explanation.

  14. #14
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    Mike,
    I am a bit confused. My system was installed a few months after yours, I believe. I also have no charge this month for power, used 728 kwh and produced 1064 kwh. At the end of the year I can choose to have any extra refunded to me, but it will be at the rate of 3 cents per kwh, not the going rate. I have chosen to keep the credit to apply to my bill for whenever I may owe them.

    About the distribution costs, on page three of the bill I find a fee called delivery charges, which I assume is distribution cost. It is very minor, at 93 cents a month, but it must be paid separately. I just sent them $20 and let them keep track of when I need to pay more. As of this month, I still have a small credit of 12 cents, so next month will be time to send them another $20.

    My system has a payoff of 4 1/2 years. It is about 18 months old, and is slightly ahead of schedule. My first full year, I generated a little more than I used, including charging my plug in Ford C-max. I understand the newer systems are even more efficient.

  15. #15
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    [QUOTE=roger wiegand;2333199Our system now makes about 40% of the power we consume and is on track to pay back in ~6 years, about a year sooner than their estimate--maybe sooner, since our local electric company just got approval for a 27% rate increase.[/QUOTE]

    6 years?

    Even with the rate increase we anticipate,
    my ROI was 25 years.

    It wasn't compelling enough to put holes in my roof.

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