I did do the reading. It's an O(n) db insert. The blockchain's the DB and the insert needs PoW.
throughput of a blockchain is contingent upon tweaking but for the original bitcoin, still used, it's 6 mb/hour. electricity consumption is 14 gigawatts. if i were given 14 gigawatts of electricity i think i could do better than 6 megabytes/hour.