I would like some help deciding what makes sense for our installation. We need a new roof [soon - ours is >30 years old but we currently have no active leaks], and our federal solar tax rebate starts cutting back next year, so we are in the market for both a new roof and solar.
I have in-hand solar proposals from two local companies. I asked each company for 4 quotes - two optimal (the # of panels they recommend), one quote using a ‘good’ panel and one with a ‘premium’ panel, and two maximized (if we installed an absolute max number of panels) – also good vs premium panels. Both came back with LG Neon R or Neon 2 for the premium panels; one recommended Hanwha Q-Cells as the ‘good’ panel and the other’s alternative was Silfab SLA-M panels.)
The differences in their proposals are striking and interesting: one company proposed 16 vs 25 panels (optimal vs max, 5 vs 9kW system), and the other proposed 37 vs 56 (11 vs 18kW system)! Also, the azimuth and roof pitch reported each proposal is very different. Azimuth varied by ~25º and pitch by ~20º. Our house/front roof is oriented ~160º south (according to my iPhone), and is about 40% shaded by trees in the spring/summer/fall. The front roof is steeper than the back roof.
So… I have a LOT of questions:
- Does the difference in azimuth stated in each proposal matter very much to the calculation of how much energy we will harvest? What about the pitch degree?
- Why/how could each company recommend such differently sized systems?!
- I don’t see anything about Silfab panels on your site, although their panels did well in the PVEL tests.
- How do we choose between the different panels proposed? Are Hanwha Q-Cells better at managing collection in shady areas, better for our roof than the longer-warranty of the LG Neon-R or Neon-2?
- How much tree-shade is too much for a panel to harvest sun?
- If we go with LG, how do we choose between Neon-R vs Neon-2?
- Does it make sense to cut down any trees to maximize solar? We are very reluctant to do that…
- How much does panel wattage matter?
- Does panel weight matter?
Then there is TESLA…my husband thinks we should consider signing up and waiting for their glass tiles - do they manage shady areas well? (I can’t find any technical information about them.)