PV panels on the roof or in the yard?
I am in the process of designing a new house and I am trying to decide whether or not to place the PV panels on the roof or in the yard. I would assume it is more cost efficicent to have the panels installed on the roof by avoiding pouring the concrete pad and having the power trench ran to the panels. I have not started getting price quotes for either system as of yet but I am hoping to get into that soon. I would just like to make a decision as to where I want the panels to go first. One side of the roof of the house will be facing southwest. Also, are most people leasing these panels still or are they buying them? I would be skeptical to lease the panels and would much prefer to own them if it is cost effective. Any thoughts would be appreciated. The house is in Connecticut.
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Replies
1. Buying your system is better than leasing (assuming you can afford the cost or obtain reasonable financing terms).
2. A ground-mounted system is better than a roof-mounted system (because re-roofing and snow removal are both easier).
-- Martin Holladay
The tide has turned, and in 2016 more people were buying (with 20-30 year warranties) than leasing, for good economic reasons.
The economics of building out a separate structure for ground mounting varies (a lot). Get it quoted both ways. In CT there is less need for manually clearing snow than in cooler parts of New England, especially if your roof is 4:12 or steeper to enhance the avalanche potential rather than relying on melt out. Coastal CT can count can melt out, but higher elevations in central or NW CT it takes a bit longer.
When done right the roofing should last as long or longer than the PV. The roofing shaded by the PV is more protected from the elements, and will usually outlast the more exposed sections of roof.
I'd be careful with asphalt shingles. The warranties are misleading and a reasonable guess is 20 years (depending on various things). Compare this to solar panels that are likely to be working well past 30 years.
If you decide on a roof-mount, check out the cost difference between a 25-year and a 45-year metal roof. On my house, the longer warranty was only an $800 difference in cost.
I would definitely buy. The lease salespeople were very short on details, so I bought. I priced a ground mount and it was more expensive. I also did not want the hassle of weeding and mowing around the posts. I put my system on a metal roof on an outbuilding. It was a through-fastened metal roof so the mounting points are primarily protected from leaking by caulk, which is not something I would do on my house. A standing seam metal roof is a better choice. The mounting design for shingle roofs is ok, too.
I'd talk to an installer and get prices for both roof and ground mount. The installer will be able to tell you whether trees will interfere with solar panels at various times of the year; whether your house orientation to the Southwest will be a significant limiting factor (as opposed to directly South); where the best place for a ground mount is; what sort of roof penetration would be needed, if any; what the optimal roof pitch is, etc.
We ended up going with roof mount, but ground mounts have advantages. Our panels are on the back of the house and basically invisible as the land slopes steeply in the South side. A ground mount would have gone somewhere in the front where it would either be in our direct line of sight from the house or would have required a long trench to get it out of sight.
There was a good Q&A on this general topic in an earlier thread:
https://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/solar-now-or-later
I thought the installer's comments were helpful, including making sure you get an engineer's stamp on the roof designs to make sure it can take the additional loads (wind and snow).
IMO, if you have the room, a ground mounted array avoids a lot of potential drawbacks of roof mounted, and allows more design freedom. If you build a separate garage, mounting on that roof would be my #2 option.