Graffi
Posts: 405
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Leaf Number: 414757
Location: San Diego, CA

Need Solar Panel recommendation

Thu Oct 29, 2015 3:27 pm

We have an 11 year old 5kw system that had two 2.5kw SMA Inverters. One of them failed so we got a new SMA 5kw inverter, but now we still have an unused 2.5kw inverter, even though it is 11 years old it still works. Also, in the two weeks the inverter has been working it only gets as high as 4kw. Our current panel array is on the hill behind the house.

I would like to add more solar panels on the house roof. I could either add 2.5kw of panels for the older inverter, or add 1kw of panels to bring the 5kw inverter up to capacity. It has the ability to wire in two solar arrays so I could still use the excess capacity of the new 5kw inverter.

What are your recommendations? The hill points SE so I could have the rooftop array point SW and therefore maximize daily production.

Any help is appreciated. Also, where can I find the best value in buying solar panels?
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Valdemar
Posts: 2412
Joined: Tue May 10, 2011 10:32 pm
Delivery Date: 09 Sep 2011
Location: Oak Park, CA

Re: Need Solar Panel recommendation

Tue Nov 03, 2015 11:25 am

Array oversizing relative to the inverter is a standard practice, I suspect you can add 2kW panels if not more to the 5kW inverter with no ill side effects considering you have an older existing array that has lost some output over time. Make sure you don't mix old and new panels on the same string, if impossible you'll need to use the 2.5kW unit with the new panels.
'11 SL, totaled
-1CB@33k/21mo, -2CB@53k/33mo, -3CB@68k/41mo, -4CB(41.5AHr)@79k/49mo, -5CB(38.85AHr)@87.5k/54mo
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2k1Toaster
Posts: 413
Joined: Mon Nov 18, 2013 5:45 pm
Delivery Date: 12 Nov 2013
Leaf Number: 420903

Re: Need Solar Panel recommendation

Tue Nov 03, 2015 10:01 pm

Also keep in mind in October those panels are most likely not pointed for maximum collection, that was mostly likely a couple months ago. It is more likely to be just part of the seasonal drop from fixed mount panels vs. panel degredation.

As to panel recommendations, it is up to your style. You can buy some super cheap chinese stuff that will work most likely trouble free for years, then spontaneously die out of warranty not that it would be worth anything to send a crate back to China... Or you can buy something more expensive from a big company with a real warranty and they too will most likely work trouble free for (more) years and then keep on working gradually fading until *you* die.

I have 4 Sharp panels that have been used and abused and they are great. I also have 39 Canadian Solar (cheaper) that have been going for over a year but have a generous warranty that might be usable if needed because of the closer location.
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Valdemar
Posts: 2412
Joined: Tue May 10, 2011 10:32 pm
Delivery Date: 09 Sep 2011
Location: Oak Park, CA

Re: Need Solar Panel recommendation

Tue Nov 03, 2015 10:16 pm

You almost never see nameplate power output from solar panels, that 5kW array was probably making 4.5kW tops on a good day when new, so 4kW after 11 years sounds about right.
'11 SL, totaled
-1CB@33k/21mo, -2CB@53k/33mo, -3CB@68k/41mo, -4CB(41.5AHr)@79k/49mo, -5CB(38.85AHr)@87.5k/54mo
-0CB(66.14AHr)@87.5k/54mo (BBB)
59.7AHr, SOH 93%, 118k miles
9kW Solar

freeewilly
Posts: 33
Joined: Tue Jul 08, 2014 3:34 pm
Delivery Date: 08 Jul 2014

Re: Need Solar Panel recommendation

Mon Nov 09, 2015 4:04 pm

Newbie question. Can you have 2 different solar panels connect to a centralized (string) inverter?

The downside of centralized inverter is produce less power or stop producing power altogether when shading happens. When you combined old and new solar panels together, will the old panel reduce the performance of the new solar panels??

Valdemar
Posts: 2412
Joined: Tue May 10, 2011 10:32 pm
Delivery Date: 09 Sep 2011
Location: Oak Park, CA

Re: Need Solar Panel recommendation

Mon Nov 09, 2015 4:55 pm

freeewilly wrote:Newbie question. Can you have 2 different solar panels connect to a centralized (string) inverter?

The downside of centralized inverter is produce less power or stop producing power altogether when shading happens. When you combined old and new solar panels together, will the old panel reduce the performance of the new solar panels??


Just as with shading, if mixed on the same string your total output will be limited by the weakest panel on that string.
'11 SL, totaled
-1CB@33k/21mo, -2CB@53k/33mo, -3CB@68k/41mo, -4CB(41.5AHr)@79k/49mo, -5CB(38.85AHr)@87.5k/54mo
-0CB(66.14AHr)@87.5k/54mo (BBB)
59.7AHr, SOH 93%, 118k miles
9kW Solar

smkettner
Posts: 7006
Joined: Mon Aug 09, 2010 10:13 pm
Delivery Date: 26 Feb 2014
Location: Orange County, CA

Re: Need Solar Panel recommendation

Mon Nov 09, 2015 10:27 pm

My system installed new has 3kW on a 2.5kW inverter.
Very rarely hits close to max and I believe the inverter would just self limit giving you a short flat spot in the day's production.

So that is what I would do be cause I actually did. Put another kW on the large inverter too if needed.
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EV4Taos
Posts: 40
Joined: Mon Nov 19, 2012 5:00 am
Delivery Date: 19 Nov 2012
Location: Taos, NM

Re: Need Solar Panel recommendation

Thu Nov 12, 2015 9:56 pm

LG 310w panel are a good value. 25 warranty from a 2 billion dollar company that is not going out of business any time soon. Pretty close to Sunpower panel efficiency too.

robertcuevas
Posts: 2
Joined: Tue Nov 24, 2015 6:20 am
Delivery Date: 24 Nov 2015

Re: Need Solar Panel recommendation

Wed Dec 09, 2015 3:25 am

I think your idea is correct as recently, our NYC HVAC service guy installed 3kW on a 2.5kW inverter. It is working properly and does not have any issues. I would suggest that once take suggestion from your contractor.

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