> Has anyone done more detailed numbers on costing of roof mounted installation vs just putting utility scale solar on the ground? You're far cheaper on the gr

> Has anyone done more detailed numbers on costing of roof mounted installation vs just putting utility scale solar on the ground? You're far cheaper on the ground, for a variety of reasons (at least in most areas). A good ground mount install should be able to come in around $1/W, and you'll have a hard time getting roof mount below closer to $1.50 or $2/W installed, and if you get $2/W, you're getting a great deal. If you're doing the work yourself, ground mount for around $1/W is doable (including the frames), but roof mount I've not been able to get below about $1.25/W, and that's hard - $1.50/W is more typical. The main difference is that the roof mount system requires rapid shutdown on (in NEC 2017 and later) every panel, and you're limited to 600V (though with rapid shutdown requirements, this is less relevant). For a ground mount system that's isolated away from random people (fenced area), you can run up to 1500VDC to the inverters, and this rather reduces your costs in wiring. You also don't need rapid shutdown, so you can just run strings of panels (20 or 25x 72 cell panels in series, depending on the environment). Also, if those strings have an arc fault somewhere, you're not going to burn up much that matters for a big ground mount install. You'll cook a couple panels, and that's about it. A fire under the panels on a warehouse is a much bigger deal. The main problem you run into with warehouses, though, is that there's just no good option for mounting. For a flat roof, they're generally built to exactly the loading requirements for the area. You don't have the spare PSF capacity for a ballasted mount, which means that assuming you've got the weight rating for the panels, you're looking at a lot of roof penetrations on a flat membrane roof to hold stuff down - and the odds of some of those leaking is basically 100%. Plus it's a royal pain to work on roof mount systems.