About to drill through the roof to mount solar panels- tips?

Make sure when you drill through the roof that there are no wires underneath. I found out the hard way. My TC does not have a fridge vent so had to find an alternate location for the combiner box I found a spot above the plumbing chase to drill through except that I was unlucky enough to hit a pack of about a dozen wires. Knocked out my AC the speakers and cable lead. Wasted about 4 hours splicing the wires back together again. It has been over a year and there have been no leaks.