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sergeykoren

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Reply with quote  #21 
Quote:
Originally Posted by Rick H Parker

You would need to look at what your net metering credits are worth and figure out if the cost of a bigger inverter is justified. This is not a technical issue, it is a financial issue.

Installer did not tell exact size of the inverter. Contract says system size - 7.6kWh.
Project still not closed and i believe i can ask installer to replace inverter. I just need to understand for myself if this will be right thing to do and i will not get any technical issue or my production will go down because of changing inverter

Rick H Parker

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Reply with quote  #22 
With a bigger inverter production will go up.
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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
stmbtwle

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Reply with quote  #23 
Looks like the installer tried to cut corners on you.  Agree production should go up.


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Willie, Tampa Bay
colinmcc

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Posts: 154
Reply with quote  #24 
Rick, unless my understanding is wrong,(?) power generated is the area under that graph, so  having a bigger inverter would only add a small period of time where the graph might go above the 5kw clipping point. and the power in that section of the graph would only be a few % points more than now. If the graph showed output starting to clip at 9am and drop back down at 4pm then I'd agree that a significant amount of output might be achieved by upping the inverter, but in the case of the poster's graph not much would be achieved for the extra inverter expense.

As an example Enphase routinely recommend a 215w inverter as the correct pairing for  a 250w panel. That's what I have on my 50 panels, I could have gone for their 250w inverters but everything I read at the time indicated the lower rating was cost effective.

And, in my limited experience the rated output of a panel, as measured under standard test conditions, is never achieved in the real world, with all the things that can affect output such as temperature, soiling, PID etc, I doubt the 7.6 kw  rated panels will ever even get to 7.0 kw on a sunny day with a cooling wind! 

Now, of course if the bigger inverter is swapped in for free then it might be justified, but the actual extra power produced might be (very) small.



stmbtwle

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Reply with quote  #25 
Exactly. As always, it boils down to the money.

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Willie, Tampa Bay
colinmcc

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Posts: 154
Reply with quote  #26 
"Exactly. As always, it boils down to the money."  [thumb]
Gordy

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Reply with quote  #27 

"Exactly. As always, it boils down to the money."

Many times yes, but not always. You have the "Close enough crowd" and the "Max it out crowd"

Utilities do screwy things. Could they be driving this design? To lower the peak output and extend the 5 kw run time?


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Gordy,
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Rick H Parker

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Reply with quote  #28 

Could they be driving this design? To lower the peak output and extend the 5 kw run time?

I figure it was to keep people from complaining "my inverter not putting out what it should".  Sometimes dealing with people that don't understand can wipe out a profit margin.

Contract says system size - 7.6kWh.

7.6 kWh is a 7.6 KiloWatt-hours of energy not 7.6 kW of power.


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Rick H Parker
Kansas, USA
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stmbtwle

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Reply with quote  #29 
That can't be right. If all that's contracted for is 7.6kwh of energy (per day? Month? Year?) you could do it with a MUCH smaller system.

Salespeople can do strange things with words.


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
colinmcc

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Posts: 154
Reply with quote  #30 
"Contract says system size - 7.6kWh."   That should read 7.6kw, which  is a measure of the potential power generation at any point in time, I assume that the original poster made an error in adding the 'h'..[smile]  Perhaps he can check his quote and confirm?
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