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Thread: How many watts in solar panels do I need for my grid tie system

  1. #1
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    Default How many watts in solar panels do I need for my grid tie system

    I use about 1000 kilowatts a month in summer and 1200 kilowatts in the winter. This is really not very much, but I would like to cut it in half. I am thinking of a direct grid tie. My small house draws about 1000 watts during the day/night hours during summer and 1200 watts during the day/night in winter. These are averages I have taken with a meter.

    What would be the total watts I would need in solar panels to cut my kilowatt use in half using direct grid tie?

    Would the Enphase Micro inverter or the SMA Sunny Boy 700u work for me? Where do they tie-in to my grid?

    Thanks
    Azel

  2. #2
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    Need -

    1) Your approximate location - and or zip code

    2) Any shading problems?

    3) Good southern exposure?

    Russ

  3. #3
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    Quote Originally Posted by russ View Post
    Need -

    1) Your approximate location - and or zip code

    2) Any shading problems?

    3) Good southern exposure?

    Russ
    Central Texas
    No shading problems
    yes

  4. #4
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    Default

    Go to PV watts (link on home page)
    Plug in your zip code, tilt of roof and azimuth of array and play around with array size to come up with a system size that would work for you.
    In most cases the PVwatts will come up with a larger array than actually needed as the derate factors are fairly high but we can go into that once some system parameters and equipment is chosen.
    Rich
    WWW.solarsaves.net

    NABCEP certified Technical Sales Professional

    http://www.solarpaneltalk.com/showth...Battery-Design

    http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

    www.gaisma.com

  5. #5
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    Another online calculator with a few more buttons comes from Sharp http://sharpusa.cleanpowerestimator.com/sharpusa.htm

  6. #6
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    Default

    I want to thank you both for the links.

    It looks like I would need to install 5000 watts in solar panels to cut my monthly electric bill in half. That is a lot more than I had planned on.

    I may go to my Plan B. I had thought about installing electrical conduit in my trailer and making a second power circuit that is solar/battery only. I would plug in small wattage draw appliances like refrigerator, lights, computers, but not big wattage drawers like air conditioners, electric heaters. I would leave heavy watt drawing appliances on gird circuit and run the small watt drawing appliances on solar circuit. In a house this would probably not be practical, but in a trailer, it would not be much trouble to install conduit externally where wall and ceiling meet the full length of the trailer with conduit branch downs to appliances. This would include:
    Lights
    fans
    conputers
    microwave
    refrigerator

    I don't suppose this would help lower the monthly electric bill to half as I had planned, but it would help. My air conditioner (in summer) and electric heater (in winter) are the appliances that really draw the watt hours.

  7. #7
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    Placerville, CA. In the Sierra Foothills, around 2000 ft. altitude, occasional snow.
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    Quote Originally Posted by Azel View Post

    I don't suppose this would help lower the monthly electric bill to half as I had planned, but it would help. My air conditioner (in summer) and electric heater (in winter) are the appliances that really draw the watt hours.
    Actually, it would come out a lot worse than the same amount of panels in a grid-tie application since you would have the extra cost of the batteries, which would not last forever either. You will end up paying at least 5 times as much for the solar electricity for your trailer as you would to leave the same appliances on the grid.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

  8. #8
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    Quote Originally Posted by inetdog View Post
    Actually, it would come out a lot worse than the same amount of panels in a grid-tie application since you would have the extra cost of the batteries, which would not last forever either. You will end up paying at least 5 times as much for the solar electricity for your trailer as you would to leave the same appliances on the grid.
    Thank you for the information.
    I better go back and do some more reading in my solar power books.

    I think I will end this string and make a post in the General section with my thoughts about the use of solar energy.


    Thanks
    Azel

  9. #9
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    Round Rock Tx / Afghanistan
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    Axel, don't give up yet. I live in central Texas as well (round rock). Depending on who your electrical provider is there are some really nice rebates available to help you get solar installed, as well as the tax credits. I just finished my install of a 10kW system on my roof. Total cost was 37 and some change. By the time I got all the rebates the cost to me was about 13k and I will get 4k and some change tax CREDIT on my returns next year. Bringing my total cost to about 8k. Let me know if you want more specifics and I will give them to you.

    Quote Originally Posted by Azel View Post
    Thank you for the information.
    I better go back and do some more reading in my solar power books.

    I think I will end this string and make a post in the General section with my thoughts about the use of solar energy.


    Thanks
    Azel

  10. #10
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    Default Please don't get mad.

    Quote Originally Posted by inetdog View Post
    Actually, it would come out a lot worse than the same amount of panels in a grid-tie application since you would have the extra cost of the batteries, which would not last forever either. You will end up paying at least 5 times as much for the solar electricity for your trailer as you would to leave the same appliances on the grid.
    Please do not take this the wrong way, I've already had that happen here. I'm just curious, I understand the old "truth hurts' thing but... you guys here are Big solar guys, why do you poo poo other people when the have an interest in going solar. Like I said to start please don't get mad. I'm just wondering why I keep hearing "It's too expensive, you might as well stay on the grid."

    I believe there is always a way you just need to find it.

    Is it that you guys are just sick of explainig that there is more involved in getting started than most people think?

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