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Im a newbie and i need help with planning my system

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  • #46
    Originally posted by Living Large View Post
    The way you normally plan for 100% is to plan for sufficient power on Dec 20. For Cleveland, the year round average is 4.0 hours of sun. But in winter, the average is 2.7 hours. So right there, you would be at about 100/2.7 ~= 37kW of PV. And that is the average for all of winter. As Sunking said, you may be on the "light" side at 25kW, so to speak. If your efficiency is 90% (I don't know what is typical), you may need more like 40kW of PV.
    And that right there would do it on my space haha.. Well tho the space may become an issue. If I was to continue and wanted to do a generator bit I would only need it for a weeks worth where should I look for something like that?

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    • #47
      Originally posted by shadowaxe356 View Post
      What would be the cost difference in the system be if I did 80%? The 3000kw a month is December bills. I would really like to go 100% or like 99.9%. I essentially do not want to give any money to the power company's, I mean a few $ in December or when the panels are acting up sure but if I can I want 100%. If the cost diffence in a 20KW system and 30KW is only like 10k then ill take the 100%. I may sound dumb but 100% is my goal. I have been looking on Alibabi.com and found a few grid tie systems with no generator ranging from $12k - $45k for 30kw systems. When looking at panels how do I know they will be worth it? I have seen many "name brands" on sale but a few off brands with better numbers for cheaper, and I cant really trust a salesman in this day and age so I as the people for answers?
      I am not sure what the "break point" would be in cost/coverage %. Certainly a larger kw pv system should be less $/watt than a small one but when it gets to a point that the physical size can push the boundry of available roof space. Then the installation costs can go up due to special racking and wiring.

      While you may have found some 30kw system for that price range, I believe it would be hard to find a quality system for $1.50/w before rebates. What you are doing is searching for the "cheapest" price for a very large system which may end up getting lower quality panels and inverters and less output then expected.

      Something else you need to investigate is if there is any size limit of a pv installation in your area. In some places either the city or POCO limits the array size. Bigger than that limit and it turns into a "Co-Gen" facility which has tougher regulations to meet.

      And finally I understand you want to stop "giving" the power company money but in reality installing a solar pv system (even grid tie) can take years to pay for itself which means you "give" you money to someone else all up front, where a reduction in electric use saves you immediately.

      Just a thought. I do not know the full situation of you and the other people in the home, but if you are the one paying for the electric bill maybe an incentive needs to be found for the other "users" in the home to contribute to that payment or reduce their usage.

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      • #48
        Originally posted by SunEagle View Post
        I am not sure what the "break point" would be in cost/coverage %. Certainly a larger kw pv system should be less $/watt than a small one but when it gets to a point that the physical size can push the boundry of available roof space. Then the installation costs can go up due to special racking and wiring.

        While you may have found some 30kw system for that price range, I believe it would be hard to find a quality system for $1.50/w before rebates. What you are doing is searching for the "cheapest" price for a very large system which may end up getting lower quality panels and inverters and less output then expected.

        Something else you need to investigate is if there is any size limit of a pv installation in your area. In some places either the city or POCO limits the array size. Bigger than that limit and it turns into a "Co-Gen" facility which has tougher regulations to meet.

        And finally I understand you want to stop "giving" the power company money but in reality installing a solar pv system (even grid tie) can take years to pay for itself which means you "give" you money to someone else all up front, where a reduction in electric use saves you immediately.

        Just a thought. I do not know the full situation of you and the other people in the home, but if you are the one paying for the electric bill maybe an incentive needs to be found for the other "users" in the home to contribute to that payment or reduce their usage.
        Ok thanks you for that info

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        • #49
          Originally posted by shadowaxe356 View Post
          My monthly bill is 3,000kwh. If I was to divide that by 30 days it would be 100kwh a day needed. Ohio gets 4 hours of sun a day so I divide 100kw by 4hours making 25kw an hour. so my array will be about 25kw. If that's correct math.... I was also told that my panels might have a higher output on certain days so I should get a inverter with about 25% more so I don't burn it out?
          Is your usage an average of 3000 kwh/month? Most utilities can tell you how much you use for the whole year. Then go to http://pvwatts.nrel.gov to estimate how big a system you need to provide that amount of KWH in a year?

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