Growing my setup - questions on inverters!

wilsonbh
wilsonbh Solar Expert Posts: 57 ✭✭✭
I live in Florida. I am in the process of buying a new roof and its drained me financially. I'd like to get a solar electric grid tie system but am strapped for cash for awhile.

My question is can I setup all the hardward, ie Combiner box, Inverter, etc with the intent of buying panels a few at a time? I'm still studying this but on first look, I'd like to get a Sunny Boy 6000 and add solar panels until I get up to it's capability.

Would appreciate any advice from those that know these things.

Thanks

Billy
«1

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,412 admin
    Re: Growing my setup - questions on inverters!

    I don't know the SunnyBoy specs... But most Grid Tied Inverters require somewhere between 200 and 500 VDC for normal operation.

    So, you will require a minimum number of panels to reach the minimum voltage. And as you keep adding panels, you will eventually hit the high voltage limit--then you will have to rewire back into two strings (minimum voltage) then add two panels at a time until you hit the high voltage limit again, then back to three strings (rewired again) and add three panels at a time...

    Also, as you add panels, if you want the Florida solar rebates--you would have to add panels and file paperwork every time (assuming that you can add panels to the Florida paperwork every time).

    In the end, if you are having this system installed by a contractor--solar panels are about 1/2 the cost of the system. The inverter, racking, labor, permits, etc. are the other 1/2 of the system costs. If you install everything but the solar panels, and, for example only install 1/2 of the panels up front--you still will have almost 3/4 of the system costs with 1/2 the actual power production--not a great return in your investment.

    In the end, figure out how much your system will cost you vs how much power it will produce over (for example) 20 years and compare that to your cost of power--then make your decision as to what make sense for your situation...

    Another thought... You are in Florida and, I assume, subject to hurricanes and longer term power outages (days to weeks)...

    I would look at wiring your home so that you have all the "must have power" circuits wired to one sub-panel (fridge, freezer, lights, radio, tv) and look at setting up a back power system (inverter, batteries, generator, and/or solar panels).

    You could, for example, install the sub-panel with a small generator sized to run the minimum loads (don't want to store/use too much fuel when there is no replacement fuel available during the emergency).

    Then, you could add an inverter/batteries so that you can have quiet backup power, then eventually solar panels and a charge controller as finances allow.

    One issue is that mixing Grid Tied and Off-Grid capable inverters and solar panels / charge controllers does quickly get complicated. Try to make sure that you have your plans fully thought out before you start the purchases/building.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Growing my setup - questions on inverters!

    Florida rebate must be installed by a licensed Electrican or licensed Solar Installer, no do it yourself allowed for the State rebate. It also has to be inspected ( copy of permit signed off required with application) by both your county and the electric company that your connecting too.

    Also, its a onetime, lifetime per resident on the rebate, this is to prevent abuse where someone gets a 20K rebate, tears the system apart sells the parts and then apply for another system

    As BB points out, 99% of GridTie inverters are HIGH voltage, so starting out small and growing is not really an option.
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!

    I think the real answer here is the power company AND the government does not want anyone to produce their own power. The regluations and cost push most people over the edge. I'm very close there right now....

    Billy
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Growing my setup - questions on inverters!

    Huh ?,

    I did the 20K rebate last year and the State of Florida paid for most of it. I just followed the very simple rules for the rebate program. I hired an electrician and did all the leg work for him to reduce his time and cost, the utility company charged nothing for the interconnect inspection and approval, I filed the paper work and within 6 weeks had my 20K check. I couldn't see how it could be any easier.

    High Voltage PV systems ( or low voltage for that matter ) are potentionally lethal systems and need to be installed in a code safe mannor. The Florida progam is the least red-tape of any rebate progams in the country and pay a flat 4.00 watt back.

    There is no derating of DC power, they use the factory name plate rating, un like the CEC, no maximum of percentage of system cost ( so if your a good shopper and use factory seconds from www.sunelec.com ) your final cost, even using paid professional serivces, your net cost can be close to zero!

    maybe you could go deeper into what part of the rebate program you feel is limiting or unfair?
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!

    I am at the early stages of understanding this technology. I sincerely do not see how these systems can cost even close to "zero" as you state. Would be great if I could get a quality system for a few thousand dollars on my part. For your $20K rebate, what did you install to get that?

    Billy
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Growing my setup - questions on inverters!

    5100 watts of the SunElec second's Evergreen 170 watt modules ( roof mounted ) and a Xantrex GT5.0

    Roof mount system is home-depot gutter clips and stock 2"x2" screen enclosure alumimum, a plan/layout that I drew up and paid a PE to approve for the installation ( 250.00 )

    If you go totally turn-key, you paying someone else to learn everything and pay for there overhead and profit ect.

    I pulled the permit, I did the plans, I got the PE to inspect and stamp the plans, I filed the rebate application and purchased the materials for the installation.

    Final net cost can for sure be a few thouand dollars if you do everything you can that is allowed yourself
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!
    5100 watts of the SunElec second's Evergreen 170 watt modules ( roof mounted ) and a Xantrex GT5.0

    Roof mount system is home-depot gutter clips and stock 2"x2" screen enclosure alumimum, a plan/layout that I drew up and paid a PE to approve for the installation ( 250.00 )

    If you go totally turn-key, you paying someone else to learn everything and pay for there overhead and profit ect.

    I pulled the permit, I did the plans, I got the PE to inspect and stamp the plans, I filed the rebate application and purchased the materials for the installation.

    Final net cost can for sure be a few thouand dollars if you do everything you can that is allowed yourself


    OUTSTANDING!!! This is why I'm hear, to LEARN. Did you buy a "system" or put one together? Can I ask what you have of your own money in this system you setup?

    Billy
  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    Re: Growing my setup - questions on inverters!

    There is at least one low voltage grid-tied inverter, It's the Xantrex XW Series Power System. Depending on wattage, they run on 24 or 48 volts. I am currently looking at the XW4024 inverter.

    PA has no rebates and skipped the fed rebate this year. Looking to due what you are thinking. Get a basic system and grow as needed/money is advaliable.
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Growing my setup - questions on inverters!

    yes, the XW from Xantrex and the GTFX from Outback can be gridtie, but have the added expense of batterys, mppt charge controller and all the balance of system parts that requires.

    Compared to a batteryless inverter, even with a small battery it is 2-5X the cost of a Xantrex GT
  • autoxsteve
    autoxsteve Solar Expert Posts: 114 ✭✭✭✭
    Re: Growing my setup - questions on inverters!

    From the sound of your situation it appears that Florida has a very attractive rebate program.

    California's is ok but nowhere near the amount you are referring to (20k).
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!

    I think I need to study the basics of what is required for Grid-tie in. What are the concerns about plugging into the grid other than regulation? Can any inverter do it so long as I don't exceed it's input capacity from the solar panels?

    Also, are all Florida power meters capable of net-metering? If so then just pumping electricity into the circuit breaker box should slow the meter, shouldn't it?

    Yes, I'm a newbee for sure....

    Billy
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Growing my setup - questions on inverters!

    i can tell you are a newbie. do know that only inverters approved for connection should ever be connected as you would minimumly have some fireworks. there are 2 basic types that can connect and we'll call them grid tie and grid tie with battery backup. the grid tie is more efficient, but takes a large series of pvs to obtain high dc voltages in the hundreds to operate the inverter. the battery backed grid tie has fewer pvs required, but the added expense of controllers and batteries and although lower in efficiency this one allows operations when no grid power is available(ie, backup power when the grid goes down).
    now i can't be too specific for florida, but let's face it most of it seems to be inspections and approvals everywhere. you aren't allowed to feed power to the grid without utility approvals and, due to the nature of this, electrical inspections for proper equipment and connections. if you are seriously interested you can look over some things for your state on www.dsireusa.org ,but do understand that these inverters are not the $19.95 modsines at walmart. these inverters for connection to the grid are somewhat expensive and are of a higher quality in waveform and workmanship.
    there is also some general information you might like to look over at our sponsor's store: http://www.solar-electric.com/
    if you go into the store itself you will also see the various inverters available and some of the costs of them.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,412 admin
    Re: Growing my setup - questions on inverters!

    Grid Tied inverters is as simple as 1) mounting solar panels on roof-correct number and model. 2) wire panels to grid tie inverter. 3) wire grid tied inverter to appropriately sized circuit breaker panel. 4) turn on switch and grid tied inverter will take any and all power provided by the solar panels and shove it into your home wiring, and either slow down your meter or even turn it backwards. There is nothing special that happens or has to be modified for your home (other than having a large enough wiring system to take the extra load created by the grid tied inverter).

    The non-simple part. There are a lot of rules, regulation, and safety concerns. To get the Florida rebates you have to use a licensed installer/electrician and get building permits. And you (probably) also have to get approval from the electric utility and have your meter changed (new electric meters will not turn backwards for billing--they will simply charge you for for putting power on the grid).

    Retail price--roughly $8-$10 per installed watt of solar panels. You want a system that can generate a peak of 3 kWatts (uses about 3.5kW of solar panels)? That will cost you (retail) around $28,000 to $30,000 installed and powered up at your home (numbers are very rough estimates--I have no idea if your installation will be more or less).

    You are in a sunny state, so it is a good place to install solar power. A 3.5 kW system (3 kW inverter, ~$28,000 installed, no rebates) would generate about 4,756 kWhrs per year (or offset roughly $428 per year in power at $0.09 per kWhr).

    If you want, contact a couple solar installers down your way and get a quote--should be free.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Growing my setup - questions on inverters!

    FYI, our real kWhr costs are pushing 14-15 cents in Florida... the core kWhr is less but in our "tax free income" state other things are taxed, like all utilities, electric is taxed by the local counties.

    My billed kWhr for last month was 637 kWh @ $89.30. This includes fuel surcharge, Enviormental and county/state taxes. My Solar generation was 760 kWh for the same period so net bill was a credit for the month. They use an electronic dual register unit measures power for each direction ... the kWh values are not my total use or generation but the net values.

    Only when the house uses more electric than solar is generating ( like night time ) and when solar generation exceeds the homes usage ( about 6 hours a day ) are the registers incremented.
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!
    FYI, our real kWhr costs are pushing 14-15 cents in Florida... the core kWhr is less but in our "tax free income" state other things are taxed, like all utilities, electric is taxed by the local counties.

    My billed kWhr for last month was 637 kWh @ $89.30. This includes fuel surcharge, Enviormental and county/state taxes. My Solar generation was 760 kWh for the same period so net bill was a credit for the month. They use an electronic dual register unit measures power for each direction ... the kWh values are not my total use or generation but the net values.

    Only when the house uses more electric than solar is generating ( like night time ) and when solar generation exceeds the homes usage ( about 6 hours a day ) are the registers incremented.

    Are you in a FPL area? (Florida Power & Light)

    Did they install an additional meter by your existing meter? I thought all meters ran in reverse as well as forward?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,412 admin
    Re: Growing my setup - questions on inverters!

    The old mechanical meters would run (and log correctly) both forwards and backwards...

    Now-a-days, the mechanical meters (may) have a one-way device (only reads "forwards, stops when trying to spin backwards).

    The electronic meters which will have the little "LCD Wheel" running correctly forwards or backwards with respect to consuming or generating power--but the "logging digital meter" only reads forward on each rotation of the "LCD Wheel" -- i.e., your bill increases (you owe money to the utility) no matter which way the power is flowing... You consume 1 kWh, the utility bills you. You generate 1 kWh, the utility bills you as if you consumed the 1 kWhr... (this was confirmed a few weeks ago by another person here who just had their new Grid Tied solar system installed, and found their meter was still charging them for exporting power to the grid).

    Which meter you have depends on your utility and the age of your service. And how the utility programmed your meter.

    My "new" meter (PDF manual for my meter) for Grid Tie solar is electronic and has Time of Use billing (peak is noon-6pm expensive power, any other time and weekends is off peak). It has lots of options for the utility and if I hold a magnet to the outside--I can get in a diagnostic mode and read all sorts of additional information--phase angles, power factors, line voltages, etc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!
    niel wrote: »
    i can tell you are a newbie. do know that only inverters approved for connection should ever be connected as you would minimumly have some fireworks. there are 2 basic types that can connect and we'll call them grid tie and grid tie with battery backup. the grid tie is more efficient, but takes a large series of pvs to obtain high dc voltages in the hundreds to operate the inverter. the battery backed grid tie has fewer pvs required, but the added expense of controllers and batteries and although lower in efficiency this one allows operations when no grid power is available(ie, backup power when the grid goes down).
    now i can't be too specific for florida, but let's face it most of it seems to be inspections and approvals everywhere. you aren't allowed to feed power to the grid without utility approvals and, due to the nature of this, electrical inspections for proper equipment and connections. if you are seriously interested you can look over some things for your state on www.dsireusa.org ,but do understand that these inverters are not the $19.95 modsines at walmart. these inverters for connection to the grid are somewhat expensive and are of a higher quality in waveform and workmanship.
    there is also some general information you might like to look over at our sponsor's store: http://www.solar-electric.com/
    if you go into the store itself you will also see the various inverters available and some of the costs of them.


    Yes, I'm a newbee and we all were at some point in time. I'm aware of the inverter costs. I don't want a grid tie battery system, rather prefer a non-battery system. It's unfortunate that we cannot install this equipment and then have an electrician certify it as correct. It does not look that difficult to install so why pay someone else to do it? No one can do it as good as you can do for yourself. I plan to do as much as I possibly can do and contract out as little as possible/allowed.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,412 admin
    Re: Growing my setup - questions on inverters!

    You probably can do much of the work and have a licensed electrician sign off on the work (and hire a PE to draft up the roof mounting--if used, and sign off on that too)...

    You are correct that this is not rocket science--but if this is your first trip down solar+nec+building department+local inspectors+utility lane and don't have a working relationship with a licensed (and in some states, solar RE licensed) electrician--it can be frustrating to install your first system...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • autoxsteve
    autoxsteve Solar Expert Posts: 114 ✭✭✭✭
    Re: Growing my setup - questions on inverters!
    wilsonbh wrote: »
    It's unfortunate that we cannot install this equipment and then have an electrician certify it as correct. It does not look that difficult to install so why pay someone else to do it? No one can do it as good as you can do for yourself. I plan to do as much as I possibly can do and contract out as little as possible/allowed.

    Yes you can do it yourself. You may lose some of the state's rebate by doing so (in Ca that's the case - they are also trying to get the infrastructure in place to support the industry, a wise idea indeed in my opinion).

    Roderick has assembled a website that documents his 'do it yourself' install. He lives in Southern California and did a PV gridtie system while replacing his cedar shake roof.

    you can look at lots of data he's compiled and download an MPEG4 movie of it all too right here.

    With some investment in time to educate yourself on the roof mounting methods, wiring requirements and equipment available you can put a system together yourself!
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!

    Well, my goal is 5KW, but I may be forced to go lower if funds get tight. I'd like to get a system that would allow me to add a panel or two later on, perhaps have a 3.5 or 4kw system and then increase its capacity at some future date with additional panels.

    My original question is can I get an inverter that is "oversized" or has capacity to allow for this arrangement? Seems like the SunnyBoy inverters would allow for this.

    This stuff is facinating to me, thanks for all the feedback. Finding this forum was like finding a hidden treasure....

    Billy
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Growing my setup - questions on inverters!

    other inverters may allow for some expansion, but seeing as how you specified sunnyboy you must choose one of their inverters that will deliver the max power you wish to expand to. this will probably be the sunny boy 6000us that our sponsor carries for your application. you will need to size it and choose what pvs you'll go with in doing this. their sizing tool may help you for their product. http://www.sma-america.com/solar-technology/solar-design-tools/fileadmin/images/layout/head.gif#
    i hope the link works ok as i don't remember seeing that # sign. anyway, for this type of install the pv strings will have a range as in the number of pvs acceptable to use per string. you also have to account for the number of strings it could accept and if that will supply your power goals when the strings are maxed. this takes a bit of patience and calculating differing pvs with the inverter you may choose. they have minimum voltages and maximum voltages they'll work with and that is from the specs of the vmp and voc of the pv you choose with temperature variations applied. bottom line is they are expandable, but to add just a pv or 2 would be possible only if you have a string or 2 already in place that is already operating lower than the max number of pvs. example may be a range of 11 to 14 pvs usable and if you are at 12 pvs per string already then each string can add either 1 or 2 pvs. once that max is attained a new string must be made and it must have the same number of pvs in it as all of the other strings. btw efficiency suffers a bit the higher in voltage you go so many plan their expansion to be a whole string of pvs.
    btw, i never said you couldn't do some of the work.
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Growing my setup - questions on inverters!

    Well, seeing as your tight on funds, a Xantrex GT5.0 inverter would be would leave funds for other parts of the system. the GT has one of the highest efficiencys, and comes with a built in disconnect, communications and a 10 year warranty and it is convection cooled, unlike the sunnyboy which has fans.

    Shop around, the GT5.0 can be had for ~2750.00 I'm not going to post the competitors link here as this is WindSuns home, use google or checkout "other" forums for ideas for lowest prices
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!
    Well, seeing as your tight on funds, a Xantrex GT5.0 inverter would be would leave funds for other parts of the system. the GT has one of the highest efficiencys, and comes with a built in disconnect, communications and a 10 year warranty and it is convection cooled, unlike the sunnyboy which has fans.

    Shop around, the GT5.0 can be had for ~2750.00 I'm not going to post the competitors link here as this is WindSuns home, use google or checkout "other" forums for ideas for lowest prices

    Thank you for the information. The price and capability sound good. Do you consider this a high quality inverter? I don't want to have to buy another one for a very long time. I do like the convection cooling capability. I only considered "SunnyBoy" first because a friend has one installed and it's all I know, at the moment. I'm certainly receptive to other brands. Actually, my only real requirement is the quality (capability is somewhat assumed). It must be the highest quality available.

    Billy
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Growing my setup - questions on inverters!

    Yes, its now the top selling inverter, +45,000 installed so far

    I have tested all the major brands, the GT is tops, most included features, widest input voltage range, lowest price per watt. Sunnyboy is a very good brand as well, but coming from Germany, its costs more and does not come with communication, disconnect and is fan cooled.

    The decending order, next would be Fronuis, PVPowered, Sharp ...
  • BB.
    BB. Super Moderators, Administrators Posts: 33,412 admin
    Re: Growing my setup - questions on inverters!

    I have one 2.5 year old Xantrex GT 3.0 max'ed out to 3kW (3.5kW STC) of panels. So far, so good.

    I would avoid fans, if you can--mechanical devices will eventually fail (usually well before anything else in a power supply/computer).

    The GT 3.0 also has a massive exposed heat sink. My inverter is installed next to my kitchen door (in my relatively cool garage) and I can always rest my hand on the heat sink in any but the hottest weather. And even then, it is just uncomfortable.

    Next to high heat, thermal cycling is what kills electronics... The lower (and fewer) temperature swings you have, the longer the devices will last.

    Just to give you an idea, a common engineering rule of thumb--for every 10 degrees C increase (18F), the life of a component (including fans) is halved. And conversely, every 10C you drop the operating temperature, the life will double.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!

    Would any of you have a "rendering" or "drawing" of your system design? I'd like to see what you did. If it's a graphic drawing, could you send it to the following address? [email protected]

    You guys are great! Appreciate all the feedback. I lap it up like a hungry dog.

    Billy
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Growing my setup - questions on inverters!

    Photos on my web pages, and sketch attached [ as a thumbnail, from permit app ]
    http://www.mike-burgess.org/PVinfo_1.html
    http://www.mike-burgess.org/PVinfo_2.html

    Mike
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!

    I'm still studying all this but here is my plan so far. I intend to purchase a Xantrex GT 5 and add the minimum panels to get it functional. Then add additional panels over time. Can this be done?

    Billy
  • BB.
    BB. Super Moderators, Administrators Posts: 33,412 admin
    Re: Growing my setup - questions on inverters!

    Yes, it can be done--within the rules allowed by your inverter (series / parallel strings)...

    Try reviewing the GT sizing tool and understand the mixture of the mfg/model of panels, adding series panels, and adding parallel strings.

    It is not so simple as you start with "5" panels and keep adding on until you get to "30" (made up numbers)... As you max out one string, then you need to start another string--rewiring the series/parallel mix as needed (and home running back to the inverter).

    Since you are in Florida and they have such high rebates ($4 per watt?), once you have installed the inverter/wiring/racks/permits/etc.--it seems that the additional rebate will pay for all of your panels (~$5.00 / watt retail).

    It does not seem to make much sense to put off the full install of panels...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • wilsonbh
    wilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: Growing my setup - questions on inverters!
    BB. wrote: »
    Yes, it can be done--within the rules allowed by your inverter (series / parallel strings)...

    Try reviewing the GT sizing tool and understand the mixture of the mfg/model of panels, adding series panels, and adding parallel strings.

    It is not so simple as you start with "5" panels and keep adding on until you get to "30" (made up numbers)... As you max out one string, then you need to start another string--rewiring the series/parallel mix as needed (and home running back to the inverter).

    Since you are in Florida and they have such high rebates ($4 per watt?), once you have installed the inverter/wiring/racks/permits/etc.--it seems that the additional rebate will pay for all of your panels (~$5.00 / watt retail).

    It does not seem to make much sense to put off the full install of panels...

    -Bill

    I am in the process of installing a metal roof. Once completed, I'll pursue the solar panel system. I'm hoping that I can keep the cost below $30K and get a $20K rebate from the State of Florida. My goal is 5KW but am flexible and would go 3.5KW if it works out as all I can do for $30K.

    Billy