Evaluating options for Solar

[rmk9785e]

The company that installed mine has a couple of offices that might be able to help you. Not very close to Lathrop, but I have to check with him to see if they can give you a quote. I'm pretty sure they can get it to you much cheaper. You should get a quote from them. At the very least, it will be a good bargaining chip for the other companies. The trick is getting into contact with the owner. He's really busy, but he can make the best deals happen. My feeling is that he's going to get bought out by one of his competitors at some point since they are losing hundreds of thousands of dollars to him in profits, so try to get in on it. But my #1 advice would be DO NOT RUSH. Make sure you have exactly what you need.

I almost made a similar mistake, until I found these forums. I'm really thankful to the people that run it and the regulars that spend so much time helping us. Their advice is really worth thousands, so thanks a lot guys for all your help!

I, too, am much appreciative of all the advice and knowledge shared by so many kind souls on this forum. It has been very helpful and I have learned much in a short time. Your advice of not rushing is pertinent.
I will contact this vendor today and see what they have to offer.

[rmk9785e]

I'm confused by the variation is quotes by vendors: Here is an example of two vendors quoting the same brand, number and size of panels, DC optimizers and Inverter:
Vendor A: Rated Size (DC STC) 5,120W, Rated Size (AC, CEC) 4,096W. Est Output 1st Year 7,872 kWh
Vendor B: Rated Size (DC STC) 5,120W, Rated Size (AC, CEC) 4,593W. Est Output 1st Year 8,143 kWh

Why is their AC rating and Est 1st year output so different?

[DaveDE2]

I would ask both of them about the descrepany. You're not going to get a better answer here.

[huge]

They are estimates. One of them is going to be closer to the actual number. There should be very minor differences between different installation techniques.

[solar pete]

Howdy some vendors choose to opt for the lower end due to the fact that when the system produces more the customer will be happy, if you have a particularly bad solar year (read lots of cloudy rainy, foggy, very hot etc) days its may be best to err on the more conservative figures and not have angry customers ringing you because the system made 2 kWh less than predicted, this is just an opinion and opinions vary

[J.P.M.]

I'm confused by the variation is quotes by vendors: Here is an example of two vendors quoting the same brand, number and size of panels, DC optimizers and Inverter:
Vendor A: Rated Size (DC STC) 5,120W, Rated Size (AC, CEC) 4,096W. Est Output 1st Year 7,872 kWh
Vendor B: Rated Size (DC STC) 5,120W, Rated Size (AC, CEC) 4,593W. Est Output 1st Year 8,143 kWh

Why is their AC rating and Est 1st year output so different?

What are the modules being proposed, mfg. and size ?

Screw the CEC rating. Go by DC STC Watts. then, run PVWatts with a 10 % derate, the proper orientations and account, estimate any shading and see what you get.

[rmk9785e]

What are the modules being proposed, mfg. and size ?

Screw the CEC rating. Go by DC STC Watts. then, run PVWatts with a 10 % derate, the proper orientations and account, estimate any shading and see what you get.

I've attached the results of my PVWatts calculations.

The modules are LG320N1C-G4. I've figured out the reason behind Vendor A's reduced ratings. This vendor offers production guarantees so by lowering their estimated output, they're hedging against lower production.

On another note, I've seen some vendors advertising "Unlike most solar companies we use 8 to 10 gauge wiring". Does this make material difference for a single string 5KW DC system to be concerned about?

[ButchDeal]

Not sure that you set up the PVWatts correctly for the optimizer arrangement:

http://www.solaredge.com/us/node/2303

http://www.nrel.gov/docs/fy15osti/63463.pdf

[rmk9785e]

Thank you for the links. Somehow the pictures of the first link don't show on my Windows 10 laptop.

[huge]

Looks like they are on the same side of the roof

[rmk9785e]

I've done the best I can to run the PVWatts analysis again (attached). Not sure where I may be going wrong.

[J.P.M.]

I've done the best I can to run the PVWatts analysis again (attached). Not sure where I may be going wrong.

For some reason, your attachments are not showing up. I get a big, black "X".

[rmk9785e]

Not sure why. I am able to see the "Attached Files" with its name and size.