$6000 solar and/or wind energy system

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greenenergynoob
greenenergynoob Registered Users Posts: 7 ✭
in Solar Beginners Corner #1
Hello,

I've been trying to research and understand solar and wind energy for residential use and I need help. What should I pick up for a system that has everything needed to start powering my home and eventually go off the grid one day. I've attached my power usage for the past 2 years and my wind speed ratings. What do you think?Attachment not found.Attachment not found.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: $6000 solar and/or wind energy system

    Welcome to the forum.

    I think I see a peak usage of something like 2,400 kW hours in January 2014. That would be 80 kW hours per day. Sounds like you are heating a hay barn with electric. :p

    If that number is right (it's hard for me to make out graphs) you would be better off spending your $6,000 on conservation. Off-grid power comes at an enormous cost and at this point is not going to compete with the grid no matter what. Imagine paying $1-$2 per kW hour.

    Wind power is even less likely to be worth the investment than solar. It is inherently problematic and costly. And it needs more maintenance.

    Invest your first $30 in a Kill-A-Watt meter and start checking everything you plug in under normal usage. Look for those loads that are killing you. Get an energy audit done if you can. Conservation benefits you no matter what you power source is because you use less, which is always cheaper regardless of the cost per unit.
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #3
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    Re: $6000 solar and/or wind energy system

    That would be a huge system. Someone recently asked about the same thing around the same usage.
    I think the estimate was around $250,000 for a complete solar setup.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,440 admin
    #4
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    Re: $6000 solar and/or wind energy system

    Notice that your wind speed chart is at 80 meters or ~265+ foot high... Most home systems are built with 60-90 foot towers. So, the wind at those levels is going to be a bunch less.

    Using PV Watts for Rochester Mi. with a fixed array tilted to 45 Degrees:
    Month Solar Radiation (kWh/m 2/day)
    1 3.85
    2 4.72
    3 4.97
    4 4.91
    5 5.74
    6 5.91
    7 5.89
    8 5.64
    9 5.21
    10 4.28
    11 2.95
    12 2.85
    Year 4.74

    You don't have a lot of sun, but you have pretty reasonable sun for the far north--minimum of 4.28 hours of sun (October) if you dump the bottom three months.

    And, unfortunately, your high power usage is right smack dab in the middle of winter.

    I guess much of your power usage is heating? Insulation, more insulation, double pane windows, high efficiency heat pumps (ground source may be first choice, but overall, air source may be as cost effective because you don't need the trenching/wells/pumping that ground source uses).

    There are folks that use solar thermal (hot water) for heating even deep into winter with snow on the ground--so it is possible:

    Solar Shed and other Solar Thermal Links

    There is no way that you will be able to use solar electric power to reduce your winter power bill in any meaningful/cost effective way. Your summer usage is actually pretty reasonable (~2,500 kWH per month?)--So your home/people are pretty conservation minded.... You just need to look at winter.

    Just to give you a rough idea if you wanted to go "all in" on solar (and for a degree wind) for an off grid system based on your present power usage.

    Battery bank: 2 days of storage and 50% maximum discharge:
    • 2,500 kWH per month / 30 days per month = 83.3 kWH per day = 83,300 WH per day
    • 83,300 WH per day * 1/0.85 inverter eff * 1/48 volt battery bank * 2 days storage * 1/0.50 max discharge = 8,167 AH @ 48 volt battery bank
    A pretty big battery bank (actually, very big).

    And to recharge the battery during winter:
    • 83,300 WH per day * 1/0.52 system eff * 1/2.85 hours of sun (December) = 57,208 Watt solar array
    While this system would just about "break even" in December, it would be hugely over-sized for your non-winter power usage (around 500 kWH per month).

    While it is possible to "do anything"--Practically speaking, look at reducing your AC winter power usage first (and/or look at changing over to alternative fuels--if they can save you money).

    Also, take a look through this thread--There are links to lots of other sources of information (conservation, alternative energy and home design, etc.):

    http://forum.solar-electric.com/showthread.php?5556-Working-Thread-for-Solar-Beginner-Post-FAQ

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • pleppik
    pleppik Solar Expert Posts: 62 ✭✭✭✭
    #5
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    Re: $6000 solar and/or wind energy system
    greenenergynoob wrote: »
    Hello,

    I've been trying to research and understand solar and wind energy for residential use and I need help. What should I pick up for a system that has everything needed to start powering my home and eventually go off the grid one day. I've attached my power usage for the past 2 years and my wind speed ratings. What do you think?Attachment not found.Attachment not found.

    I agree with what everyone else has been saying, and I'll add a couple of things since I'm in your neck of the woods (Twin Cities)…

    First, it looks like you are using electric heat. In Minnesota, your power company is required to offer a home energy audit at a discounted price (it was $100 a couple years ago when I did mine). That should be the first thing you do. Invest a few $K in upgrading your insulation, sealing attic bypasses, etc. Your ROI on this will be bigger than almost anything else you can do.

    Next, before you go solar/wind, take a look at replacing your electric heat with a ground source heat pump (aka geothermal). It's expensive (but so is solar), but it will cut your heating bill by probably 2/3. I did this five years ago, and it's cheaper to heat than natural gas--even though gas has been cheap for the past several years.

    Between those, I'm guessing you can easily trim several thousand kWh per year from your power bill.

    Then take a look at grid tied solar. Don't worry about off grid for now--it's going to be at least a decade before batteries are cheap to make off-grid worthwhile for anything except middle-of-the-woods applications.

    You can also explore small wind, but as several other people have pointed out, wind isn't economical for smaller systems. It only gets cheap when you can build a 500-ft turbine. Solar works much better than wind for residential-scale systems.
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  • jebatty
    jebatty Solar Expert Posts: 56 ✭
    #6
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    Re: $6000 solar and/or wind energy system

    Check out some info on my system, all grid-tied: http://forum.solar-electric.com/showthread.php?22848-6-5k-System-A-Wise-%28Investment%29-Decision-IMO

    My annual PVWatts is 4.2, a little less than yours, and I'm at 47* north latitude; system is fixed at 34* from horizontal, maximized pretty much for summer production - a very good choice for northern latitudes IMO. There are significant incentives in MN, one is the 30% federal tax credit, plus incentives from investor owned power companies, plus maybe others depending on your situation. Also MN requires utility buy-back on grid tied systems at the average retail rate, which is the rate you would pay for general electric service. The buy-back is a credit on your bill, which also means you eliminate sales tax at the same time on "saved" non-use of grid electricity. Further the MN PUC is moving towards new regulations which likely will up the buy-back rate by costing the real benefit of solar electric over grid electric. The new regs are expected fairly soon. I wish you well on your adventure.
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  • greenenergynoob
    greenenergynoob Registered Users Posts: 7 ✭
    #7
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    Re: $6000 solar and/or wind energy system

    If it doesn't need to be plugged in or not in use its unplugged and if a whole circuit doesn't need to be on I have it off.

    I ran the a/c for 2 weeks last year.

    I'm going to be checking the attic insulation this week.

    I'm told I'be been getting by pretty cheap for an all electric, no gas home.

    Is it a must that I switch my heating system?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,440 admin
    #8
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    Re: $6000 solar and/or wind energy system

    I would talk seriously with a heating contractor--Both about your heat source and level of insulation in your home.

    The big problem is you use almost 5x as much electricity in winter vs summer--And you get ~1/2 the hours of sun per day in winter...

    If you size the system for "summer", you will not even make a dent in your winter heating (assuming that is your major load).

    If you size the system for "winter", you will have almost 10x the amount of power needed to run your summer loads.

    Just to give you an idea, PV Watts for 60 degree tilt (winter position):



    Month
    Solar Radiation
    (kWh/m2/day)


    1
    3.73


    2
    4.91


    3
    4.77


    4
    4.69


    5
    4.52


    6
    4.81


    7
    4.98


    8
    5.01


    9
    4.63


    10
    3.92


    11
    3.13


    12
    2.96


    Year
    4.33




    December 2.96 hours (average) of sun, 83.3 kWH per day:
    • 83.3 kWH per day * 1/0.77 panel+controller derate * 1/2.96 hours of sun = 36.5 kWatt solar array

    And, for many locations, >10 kWatt is more than many utilities/state PUC's will allow for a residential GT power system...

    You (maybe?) could save substantial amounts of power if you have a ground sourced Heat Pump system--But that is not cheap, and requires a fair amount of work for the heat exchange field/wells/etc.

    Could you save 1/2 of the power costs--Maybe. But that is why HVAC contractors make the big bucks.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • greenenergynoob
    greenenergynoob Registered Users Posts: 7 ✭
    #9
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    Re: $6000 solar and/or wind energy system
    jcheil wrote: »
    That would be a huge system. Someone recently asked about the same thing around the same usage.
    I think the estimate was around $250,000 for a complete solar setup.

    Thanks for your feedback. I've learned that the most watts I can have in panels is 8300 (STC) with a 7500watt inverter. What is the largest watt per panel I would be able to go? A company I talked to suggested 230 watt panels but if I can generate more power per square footage, why not?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
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    Re: $6000 solar and/or wind energy system
    greenenergynoob wrote: »
    Thanks for your feedback. I've learned that the most watts I can have in panels is 8300 (STC) with a 7500watt inverter. What is the largest watt per panel I would be able to go? A company I talked to suggested 230 watt panels but if I can generate more power per square footage, why not?

    Larger Watt panels tend to be larger panels. There's no magic in making more Watts per square foot: monocrystaline panels are more efficient than polycrystaline panels by 2-4%, and that's about all you can do there.
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  • greenenergynoob
    greenenergynoob Registered Users Posts: 7 ✭
    #11
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    Re: $6000 solar and/or wind energy system
    Cariboocoot wrote: »
    Larger Watt panels tend to be larger panels. There's no magic in making more Watts per square foot: monocrystaline panels are more efficient than polycrystaline panels by 2-4%, and that's about all you can do there.
    When deciding the watt/size of panels I'm sure I would have to figure what would fit best in the dimesions of the roof I plan on mounting it but does the watt/size also need be considered for the inverter you use, wire guage, size of main you have or anything else? I have a 200 amp main.
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #12
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    Re: $6000 solar and/or wind energy system

    For $6000 you will probably not have an issue with a 200 amp main. Have you decided on micro inverters or a central inverter?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
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    Re: $6000 solar and/or wind energy system
    greenenergynoob wrote: »
    When deciding the watt/size of panels I'm sure I would have to figure what would fit best in the dimesions of the roof I plan on mounting it but does the watt/size also need be considered for the inverter you use, wire guage, size of main you have or anything else? I have a 200 amp main.

    With a 200 Amp main service the straightforward GT install is 40 Amps: 9.6 kW or less. There are ways around this such as putting in a smaller main breaker or a larger service panel or a line side tap installation. Probably not worth investing in if you have limited space for panels.

    The inverter should closely match the array size: i.e. 8kW array and 8kW inverter. The array can be slightly larger than the inverter capacity because it will not actually put out its full rating, or at least not all the time. Any extra will be 'clipped' (lost) as the inverter limits to its maximum output.

    The wire gauge will depend on the array configuration and distance to the inverter. The configuration will also depend on the inverter's input needs, which is why most all companies have strings sizing tools for their inverters these days. Central inverters will have minimum start-up Voltage, best MPPT Voltage range, and maximum Voc input limit.

    So without changing the service you have the 40 Amp, 9.6kW limit to the system. Then you will have the limit imposed by how much panel can be fit on the roof. Remember to check local ordinances as some places set-back and access requirements which will further restrict panel space.
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  • SkiDoo55
    SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    #14
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    Re: $6000 solar and/or wind energy system

    Correct me if I am wrong it is a 40 amp max backfeed breaker in a 200 amp panel with the NEC 80% would be actual 32 amp max from inverter(s) which would be nominal 7600 watts of power out of the inverters. Inverter limits output. Can be over paneled but only put out rated power from inverter.
    9600 watt inverter would have output of @40 amp and would require a 50 amp breaker per NEC ?
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #15
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    Re: $6000 solar and/or wind energy system
    SkiDoo55 wrote: »
    Correct me if I am wrong it is a 40 amp max backfeed breaker in a 200 amp panel with the NEC 80% would be actual 32 amp max from inverter(s) which would be nominal 7600 watts of power out of the inverters. Inverter limits output. Can be over paneled but only put out rated power from inverter.
    9600 watt inverter would have output of @40 amp and would require a 50 amp breaker per NEC ?

    No, you're not wrong. It depends on whether you are considering peak or continuous current. As continuous current output it should be derated. As peak it would not be. So maximum power is still 9600 Watts but continuous would be 7600 Watts. NEC defines continuous as "3 hours or more" so it is unlikely the 9600 Watts would be sustained for that long unless the inverter was "over-paneled". Now as to which way it will be interpreted ... Keep in mind that such a system is regularly called "10kW" just to make it more confusing. Oh and you can also down-size the main breaker.

    Now the best part is the rating is actually based on the bus bar ratings so if you know that you can probably put that 50 Amp breaker in and not worry. Providing the AHJ understands this. Or "your local results may vary".
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  • SkiDoo55
    SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    #16
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    Re: $6000 solar and/or wind energy system

    Guess I am getting pretty close if net over even at this time of year. I am doing about 6.9 hrs of inverter full output in 13 hrs of on time? Does that count? Should be heading higher as we get longer and sunnier days locally. Will be the first summer with my full 9600 watts of panels on 2 ea. 3800 watt inverters. Getting about 81% Overall conversion.
    ned to reread NEC sections.

    appreciate all of the knowledge that you give out!
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
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    Re: $6000 solar and/or wind energy system
    SkiDoo55 wrote: »
    Guess I am getting pretty close if net over even at this time of year. I am doing about 6.9 hrs of inverter full output in 13 hrs of on time? Does that count? Should be heading higher as we get longer and sunnier days locally. Will be the first summer with my full 9600 watts of panels on 2 ea. 3800 watt inverters. Getting about 81% Overall conversion.
    ned to reread NEC sections.

    appreciate all of the knowledge that you give out!

    Continuous rating means output Watts over time, not accumulated Watt hours. 9600 Watts for 3 hours would qualify but that same equivalent 28.8 kW hours over the whole day would not.
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  • SkiDoo55
    SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    #18
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    Re: $6000 solar and/or wind energy system

    I am doing 50 kWH+ per day. Only 39.6 kWh today been cloudy with scattered showers.
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
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  • greenenergynoob
    greenenergynoob Registered Users Posts: 7 ✭
    #19
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    Re: $6000 solar and/or wind energy system

    Central Inverter
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  • greenenergynoob
    greenenergynoob Registered Users Posts: 7 ✭
    #20
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    Re: $6000 solar and/or wind energy system

    So, if I have the space and install within local ordinances I can have 9.6k in panels?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #21
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    Re: $6000 solar and/or wind energy system
    greenenergynoob wrote: »
    So, if I have the space and install within local ordinances I can have 9.6k in panels?

    Yes, but those are big "ifs".
    With a budget limit of $6,000 I don't think you're going to be anywhere near that. I don't know what installed prices are like where you are but I'd hazard a guess you'll be in the 2kW to 3kW range.
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  • ericsolar
    ericsolar Registered Users Posts: 1
    #22
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    Re: $6000 solar and/or wind energy system

    id say give me a call i think i can help you out!
    Eric 818 585 7592
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