This is why I have a metal roof: pay now, or pay again later... (NOTE: Labor in the future will cost more than today, it's called inflation... The typical Federal Reserve target is 2% annual inflation)
For my DIY 4.4kW array, I used Creotecc (front mount) tile hooks which conveniently duck out from under the overlapping panels of my Decra metal tile roof so I have no bolts penetrating the roof tiles. (These hooks were formerly marketed in the USA by Unirac who appears to have changed their present design) I had to come up with the tile hook concept myself. The structural engineering design on my array was required to meet wind loads of a 3-second gust wind of 170mph. My permitting package includes a signed structural engineering design showing the math behind what that means, but it's a crazy amount of potential down force or UP-lift. Drilling over 100 holes in my metal roof sounded ludicrous. What sealants can anyone name that are good for 25+ years exposed to the sun daily on a rooftop in South Florida?
I have friends in Colorado who are currently awaiting a roof replacement for hail damage suffered last summer on their asphalt shingle roof. The hail didn't damage their PV array, but the hail did apparently damage their shingles. I don't envy that position...
On our farm in Maine, I'll be doing a ground mount. I don't want any chance of a roof penetration leaking in winter, or any more reason for snow to build up on the roof. We also have a metal roof there and the snow tends to slide off before it packs up too deeply.
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