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bhavin66

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Posts: 19
Reply with quote  #11 
Thanks "colinmcc" for a more detailed response.
Now I feel both would work for me.
I will be grid tied. No batteries.
Installers designed the system at about 7kw which should be able to cover my most electricity usage.
I looked up 7kw inverter online and comes up at under 1k but as you mentioned if the inverter dies whole system is down and has to be fixed immediately.
With micro inverters I can wait and do it when time/budget permits.

Thor

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Reply with quote  #12 
I'm not sure if micros work with the 72cell panels... something to check out.

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stmbtwle

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Reply with quote  #13 
Ok now we know this is to be a residential sized grid tied system. What is the roof configuration? A roof with lots of facets and gables does not lend itself to a string configuration, as panels facing in a different plane should have a different inverter. That's not a problem with micro inverters.

Are there trees that may shade part of the roof? If so microinverters have an advantage there.

A big, simple flat or ranch-style roof not subject to shading could do well with a string inverter.

Expansion. If you later decide you need more power, adding another panel or two to a microinverter system wouldn't be that difficult. A string system might require that you replace your inverter, an expensive proposition. If expansion is to be considered an oversized inverter might be a good idea.

Safety. Grid tied inverters are, of course grid tied. In a microinverter system the 240v grid extends to the roof, and if you shut it off all the panels shut down. In a string system the high-voltage DC strings may remain "hot" to the tune of several hundred volts. Newer codes may require a roof shutoff, I don't know.

I have a 6k string system and it has worked well for 8 years. However I cannot easily expand it as my inverter is maxxed out. Were I to do this again I'd probably go with micro-inverters.



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Willie, Tampa Bay
bhavin66

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Posts: 19
Reply with quote  #14 
Thanks "stmbtwle"
It is one roof plane with 20 panels in the design.
And maybe if I can add another 4-6 on garage roof in the same direction but lower.
There will a bit of shading on the side panels from neighbors trees but that is what installers say will be taken care of by optimizers.
Only expansion possible is if I go 1 row on other side of main roof but would not be considered smart investment as that will be west facing.
So this will be the maxed out system and no more expansion.
The question arose from the first gen micros failing within 6 months or a year but the newer micros are supposed to be much more robust but I don't see a history for the claim.
Personally I like micros but the additional cost (about 10% more) and no history worries me.

stmbtwle

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Reply with quote  #15 
I have thought of installing another kw as I have the space, but would go with microinverters on a different circuit from the string inverter.
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Willie, Tampa Bay
colinmcc

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Posts: 139
Reply with quote  #16 
"There will a bit of shading on the side panels from neighbors trees but that is what installers say will be taken care of by optimizers."

Micro inverters will do the same thing, if one panel/inverter is shaded the rest will still function perfectly. 


"I'm not sure if micros work with the 72cell panels... something to check out. "

True in the past, the enphase M215IG/250IGs (their 4th generation micros) could be over powered/damaged by a 72 cell panel's output, but now their latest offerings (6th generation) do work with 72 cell panels.

7kw from 20 panels means 350w panels, presumably to get most output from that limited roof space, so you are looking at current state of the art panels and inverter(s), which means a premium price.

When you do decide which way to go please post back with the details, and if you get quotes for both systems, I for one would be interested to know what your options were.
bhavin66

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Posts: 19
Reply with quote  #17 
I am in Edison NJ. Have got a few quotes.
24 panels optimizer 22k with 20 yr labor warranty
26 panels micros 25k with 10 yr labor warranty
26 panels optimizer 24k with 20 yr labor warranty
26 panels micros 31k with 25 yr labor warranty
All these based on 20 on main and 6 on garage roof. All panel ratings are between 290w and 310w and with 25 years manufacturers warranty.
I am leaning towards max warranty as I don't have to worry about fixing for a long time, correct me if I am wrong and should save some money upfront and take the risk of fixing myself.
I don't have the money so I will be financing the system and based on the system price I can expect 30% federal rebate and SREC income after that which I have a feeling will not be more than 10k over 15 years. Financing is about 6% which adds to the system cost in way of interest and offset my saving.

bhavin66

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Posts: 19
Reply with quote  #18 
Update to the request.
I went with about 7.6kw system with a local vendor
22 lg365w panels and solaredge 7600-uss powerwall compatible inverter.
System is designed to generate about 9000kw annually which would cover 99% of my usage.
Permitting process is going on and hopefully will be installed by August 2017.
With 15 years financing the sticker price will be $25500.
bhavin66

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Posts: 19
Reply with quote  #19 
Just looking for a general view.
I am in the process of getting this system installed and I see the next gen pv panels getting available.
I asked if I can get those and I am told it would increase the price by about $2000.
Old panels lg365w panels 18.6% efficiency
New panels lg360w panels 21.2% efficiency

Is it worth spending the extra money?
stmbtwle

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Reply with quote  #20 
I think it's a matter of doing the math, how many watts for how many dollars, and how many will fit in the space available. If space isn't a problem then the more expensive panels are hard to justify.

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Willie, Tampa Bay
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