Help with Solar system

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System
System Posts: 2,511 admin
in General Solar Power Topics #1
I need to buy a 20KW solar power system for my house, but I don't know what type of inverter and solar pannel I should buy. Should I buy a 10kw inverter or four 5000W.
Should I buy 220v or 110v pv inverter since I have some appliances that required 110v while some others required 220v?
In order to generate a 20kw from the inverter, what should be the capacity of my solar pannel. Last but not least, is there any other equipment that I will need to buy.
Please let me know what you think. Thank you.
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  • arkieoscar
    arkieoscar Solar Expert Posts: 101 ✭✭
    #2
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    Re: Help with Solar system

    For a system of that size you really need to get in touch with some experienced contractors in your area and let them design a system for you.
    At the very least, you need to do some homework so that you know enough about PV to ask the right questions.
    For the people on here to answer any of your questions, you need to provide a lot more information.
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #3
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    Re: Help with Solar system

    WOW 20KW is a huge system, hopefully grid tie. I would do these steps first
    1) check your billing for how many K watts per month you are consuming
    2) perhaps get some monitoring equipment to determine when the loads occur
    3) setup up a plan for conservation, solar ain't cheap.
    4) once you have a handle on your loads and usage then determine how much you can afford to invest in solar.
    5) contact your utility to find out about grid tie options and requirements. You will be come a producer of power to they need to buy into what you are doing.

    For a 20Kw system expect to spend well over $100,000 installed. I have a 12.5 Kw system and it took a ton of cash to set it up. I run 8 tons of AC with high seer ratings. I did all the conservation measure first, like CFLs, more insulation, Energy Star appliances. It is way cheaper to save a watt than it is to generate a watt.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
    #4
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    Re: Help with Solar system

    In North America, we use "split phase" 120/240 VAC power. So, as far as your appliances and utility billing (assuming Grid Tied system and not an Off Grid battery backed system)--Your inverters will be 240 VAC. The utility and your home appliances do not care if you had 120 VAC or 240 VAC inverters--But with 240 VAC inverters, the wiring costs will be about 1/2 the price (less copper in the wires because of less current at higher voltage).

    Also with very large systems (over 3kW to 10+kW rated output), the home/small business circuit breaker panels and possibly even the utility drop are not large enough for a 20kW solar array and may they may need to be replaced/upgraded with larger components. This will also several thousand dollars. or more, to the cost of installing your system.

    The difference between 2x10kW or 4x5kW inverters--really just look at where they will be installed (do you have room) and how much will the overall job cost be... It is not really a big issue either way and is for the most part a price vs availability issue vs labor cost.

    Typically, it works out that an inverter output is around 86% of the array rated power... So, for a 20kW output, roughly:
    • 20kW / 0.86 = 23.3 kW solar PV array would be installed
    Given that you will have to use a licensed electrician and (most likely) a licensed structural engineer, as well as building permits and utility approval--Whomever you hire will be doing much of this work for you (estimating the costs and working out the installation/equipment details).

    And, you will probably be paying around $6-$7+ per watt of system or $120-$140,000+ for the system (excluding 30% Federal Tax Credits and any state/local breaks).

    Also, in some states, systems larger than 10kW may have other regulatory issues that may change the costs/economic costs of your system too (also, residential vs commercial systems may have some differences too).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #5
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    Re: Help with Solar system

    Bill is correct on all counts, I had to upgrade my utility feed and main panel for my initial 10Kw install which is suppose to be max for a residential install. That was like $4300. I slide an additional 2.5 Kw on to mine later as I sized the inverters to 12.5Kw and the utility and code guys were fine with it. Passing local code can be a big hurdle if your building dept. is not familiar. Mine was and it still took several attempts.
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  • jcgee88
    jcgee88 Solar Expert Posts: 154 ✭✭
    #6
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    Re: Help with Solar system
    macdo4ever wrote: »
    I need to buy a 20KW solar power system for my house

    As others have noted, to give you the best advice, you
    need to provide more information, including what your
    real goals are.

    Are you going to be grid tied or off grid?

    How did you determine that you need 20kw?

    Are you trying to retire some fraction of your current
    use, or are you trying generate 100% of your needs?

    Where are you located (to determine your site's
    solar exposure)?

    Roof mounted or land mounted? If the former,
    how much space do you have available?

    Does the prospective area have shading issues?

    Existing home? If so, how old? Do you have an
    up-to-date circuit breaker box? How old is your
    roof?

    What is your budget?

    --

    If you provide additional information, you'll get in
    return a lot of knowledgible advice. But, in the end,
    for this class installation, you should seek the advice
    of your local best-in-class solar installers.

    John
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