Designing 6kw System Grid Tie MicroInverter Question

KozmoK
KozmoK Solar Expert Posts: 42 ✭
in Solar Beginners Corner #1
I have found the markup on local solar companys equipment is huge, and found a good deal after many days of searching on 250w panels.

I want to use Enphase M215 or M250's.

My question is. If I am using 250W panels and I am using the M215's I am limited to 215 wats

so a 24 panel 250w system is 6kw but with the M215's its really 5160. Is it better to use the M250's and get the true wattage out of the panels? They are about $40-50 more then the M215's (which will be about $1k difference in my setup). The difference is 840w.

I feel like I can buy cheaper 230w or 240w panels if I use the M215's to yield the same results.

Also my last question is - will this forum allow a recommendation of a local installer in North Peoria/Phoenix area?

EDIT: I am in no way attempting to install this my self, nor apply for permits myself. I will be paying a contractor to do all that :)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Designing 6kw System Grid Tie MicroInverter Question

    Welcome to the forum.

    The first thing you have to understand is that a 250 Watt panel is not going to produce 250 Watts even on a 250 Watt inverter. The average output through hours of good sun is going to be more like 193 Watts. Yes, it's that bad. So whereas the 250 Watt inverter will allow up to the maximum output of the panel and the 215 Watt panel will limit that maximum, you will not actually see that much difference between the two because the panel will rarely if ever hit is rated output. It is quite common to put a 'larger' panel on a 'smaller' inverter in order that the inverter may operate near its maximum for a longer time throughout the day.

    So in essence your twenty-four 250 Watt panels is a 6000 Watt array, and no matter what inverter set-up you use (including central type) its averaged output will be about 4.6 kW over the hours of good sun (about 5 where you are) or 23kW hours per day.

    Plug your array sizing into PV Watts http://www.nrel.gov/rredc/pvwatts/ along with the other relevant data and see how changing certain aspects of it affects total harvest.
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  • KozmoK
    KozmoK Solar Expert Posts: 42 ✭
    #3
    Re: Designing 6kw System Grid Tie MicroInverter Question

    Thank you so much for your reply. I understand now :)

    This totally changed my design. I think I will buy the 240w panels and the M215's. The money saved that I was prepared to spend on the M250's It will be be best served buying a few extra 240 panels and Inverters to make up for the small loss.

    I tried the link you gave, I guess the calculator service is down at the moment giving a error when trying to use it. I will try it again tomorrow.

    Thank you again.

    Koz
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  • ARTsolar
    ARTsolar Registered Users Posts: 14 ✭✭
    #4
    Re: Designing 6kw System Grid Tie MicroInverter Question

    I think your decision to go with the 240W modules paired with the M215's is the way to go. You are definitely maximizing your inverters potential. The maximum power you will see from your M215's is going to be in the 227W range. Depending on the price difference I would not hesitate to go with the 250W modules, depending on your orientation and tilt the modules will occasionally "clip" under ideal producing conditions ie. bright clear cold winter days but most of the time you will get the extra power.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #5
    Re: Designing 6kw System Grid Tie MicroInverter Question

    I believe you have to use only Enphase approved panels to keep the UL Listing legal.

    Go to the Enphase Website and see if those panels are approved.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #6
    Re: Designing 6kw System Grid Tie MicroInverter Question
    KozmoK wrote: »
    I have found the markup on local solar companys equipment is huge, and found a good deal after many days of searching on 250w panels.
    <snip>
    recommendation of a local installer in North Peoria/Phoenix area?

    We have members and member/installers in that area, perhaps they will weigh in.

    Many installers do a lot more than sell and install systems... they often navigate the permit and incentives process. They know the idiosyncrasies of the local inspectors. Of course you get to pay for their experience when you pay their markup. We've had quite a few folks start out on their own and regret the decision to do so when they can't pass inspection.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    #7
    Re: Designing 6kw System Grid Tie MicroInverter Question

    Have you considered the likely problems you might see due to putting electronics in the incredibly hot under solar panel environment in Phoenix? I know Enphase will warranty it but why spend more on microinverters when there is this real risk?
    By the way how much markup is there in your business? You ought to see the markup the unionized utilities charge. They take 3 cent, subsidized coal-fired power and sell it to us for 12.5 cents plus tax.
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #8
    Re: Designing 6kw System Grid Tie MicroInverter Question
    BB. wrote: »
    I believe you have to use only Enphase approved panels to keep the UL Listing legal.

    Go to the Enphase Website and see if those panels are approved.

    -Bill

    Bill, where are getting this information ?

    boB
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  • KozmoK
    KozmoK Solar Expert Posts: 42 ✭
    #9
    Re: Designing 6kw System Grid Tie MicroInverter Question
    boB wrote: »
    Bill, where are getting this information ?

    boB


    http://enphase.com/wp-uploads/enphase.com/2011/11/Enphase_Module_Compatibility_List.pdf

    Thanks for the info guys! Still in need for a local installer in Peoria AZ
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  • KozmoK
    KozmoK Solar Expert Posts: 42 ✭
    #10
    Re: Designing 6kw System Grid Tie MicroInverter Question

    Yes I understand its super hot here, lived here my whole life in the sun. If they are warrantied for 25 years, then I will get a replacement from them. Maybe keeping one spare for these occasions. I like the idea of monitoring the output per panel like enphase does its pretty slick. If one goes out I will know instantly, and I will be able to pin point exactly which one.

    I am getting two more local equipment and install quotes this week. If its within a reasonable markup margin I will just go with them and not hassel with project managing myself. But the two quotes I've gotten so far, they are marking their panels and inverters up $50-60 more per then a internet quote I got on the same exact models.

    Thanks again everyone for your time.

    I am not sure what your point is about the markup.
    solarix wrote: »
    Have you considered the likely problems you might see due to putting electronics in the incredibly hot under solar panel environment in Phoenix? I know Enphase will warranty it but why spend more on microinverters when there is this real risk?
    By the way how much markup is there in your business? You ought to see the markup the unionized utilities charge. They take 3 cent, subsidized coal-fired power and sell it to us for 12.5 cents plus tax.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #11
    Re: Designing 6kw System Grid Tie MicroInverter Question

    Hmmm... Either the requirements have changed or I am mistaken. There is a compatibility calculator for solar panels on Enphase modules (says European on website, but none of the documentation says this is only for European installations).

    So--Panels just need to meet the Enphase/UL requirements, but panels do not have to be "pre-approved" or approved by Enphase.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #12
    Re: Designing 6kw System Grid Tie MicroInverter Question

    Maybe in phoenix, the temp reduces the panel output but in northern NH I see my central inverter clip frequently on clear cold days as the panels are putting out more than the rated output.
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #13
    Re: Designing 6kw System Grid Tie MicroInverter Question
    BB. wrote: »
    Hmmm... Either the requirements have changed or I am mistaken. There is a compatibility calculator for solar panels on Enphase modules (says European on website, but none of the documentation says this is only for European installations).

    So--Panels just need to meet the Enphase/UL requirements, but panels do not have to be "pre-approved" or approved by Enphase.

    -Bill

    I think they just don't want you to blow up their inverter. All GT inverters have to limit output power to ratings but put too much PV on it and it will heat up too much and then shut off.

    Notice they don't say this is to keep the UL listing. They are already listed.

    That's why they let you pick your own. Now, "AC modules" may be a different story but even then, maybe strictly not ?

    boB
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