[derangedHorse]

Just for the energy: Current hash rate is around 995m TH/s[1]. The best off the shelf miner on the market is the S21 which can hash at ~200 TH/s [2]. Assuming all of the hash rate comprised of S21s without operational inefficiency, we would have ~4,975,000 S21s hashing on the network. They also use up about 16.67 J/TH , which is 3334 J for 200TH. This is what’s expended per second.

The average time to mine a block is 10 minutes so let’s convert our J spent per block for one miner : 33346010 ‎ = 2,000,400. With about 4m of these, that’s about 8 trillion joules per block. Now if we divide that by 3.6m to get kWh, we’re back around ~2m kWh per block. Texas is about 15 cents per kWh so we get about $300k spent per block.

To 51% attack, we’d need to spend a little bit more than that. With full competition, and an attempt to mine empty blocks, it would take about $48m to attack the network for a day (144 blocks). And that’s just back of the envelope math.

Realistically, not everyone has the latest and greatest in mining equipment and probably burn more money with less efficient miners.

And all this is on top of the capex required to acquire 4m S21s, which would be around $10B at around $3k a pop.

[1] https://ycharts.com/indicators/bitcoin_network_hash_rate

[2] https://hashrateindex.com/rigs/bitmain-antminer-s21+