Choosing a solar (PV) system
Hi, I am completely new to solar and considering proposals from a couple of contractors.
One is proposing a 3.1 kW system of (9) 345W SunPower panels with a SunnyBoy inverter located on a south facing roof.
The other is proposing a 4.2 kW system of (14) 305 kW LG panels with a Fronius Primo 5.0-1 inverter, with panels located on a south facing roof plus on a basically flat roof adjacent to it.
The LG system is priced about $1500 more, but gives me an extra kW of power, which I am pretty sure I will use. On the other hand, the SunPower panels have a better warranty and higher efficiency, with less degrading over their lifespan. But the economics seems to work out in the LG system’s favor–quicker ROI.
Am having a hard time sorting out the variables. Both seem to be top brands. Any thoughts? Any advice that anyone would like to offer would be much appreciated.
Thank you!
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Replies
Nancy,
The first step is to do some research on the two contractors making the bids. Check references, and find out how long each company has been in business. If possible, talk to several customers.
It's almost always better to choose the contractor with the better reputation for service and reliability.
Assuming the two contractors have similar reputations, I would go with the system that has the lowest cost (in dollars per watt). If you like the contractor who suggested the 3.1 kW system, you could ask for a quote for a larger system, using the flat roof that the other contractor was planning to use.
I'm worried about the plan using sections that are at two different angles. If those are combined into one inverter, the inverter won't be able to optimize the operation correctly as the optimum operating currents and voltages for the different roof angles would be different. I can't be sure that's a problem without knowing more about the proposed system but it's at least worth asking the contractor how they expect it to work. I would recommend either two inverters, one for each section, or a micro-inverter based system that has a separate inverter for each panel. Perhaps they are already planning two inverters? But I would give very careful scrutiny to the credentials, references, and proposal of the contractor proposing the 4.2 kW system.