Are there any statistics on how much bitcoin miners spend, in general?
Even very rough calculations.
There's this one, but it seems pretty inaccurate and out of date:
qz.
Most of the biggest operations are private so they don't have to release numbers to public and never will. So getting accurate data is not going to happen.
Only rough estimate would be take hashrate and use a certain efficiency chip. But you can't really do this as so many different miners out there, and price of electricity varies so much. So it's a impossible task on getting right.