Let's assume for a moment bitcoin would be worth a million in 5 years. There will have been another halving, so miners will be generating 3.125 bitcoin/block. A

Let's assume for a moment bitcoin would be worth a million in 5 years. There will have been another halving, so miners will be generating 3.125 bitcoin/block. At 6 blocks an hour, that would be worth 3.125 * 6 * $1M = $18,750,000 per hour. Bitcoin miners tend to find the cheapest electricity, like near hydroelectric dams. So let's assume they can get electricity for $0.05/kwh. And to keep things simple, assume that 100% of their costs are electricity (in reality there will be capital costs and other operational costs, adjust calculation to your own liking). That means they can collectively consume 18,750,000/0.05=375,000,000 kwh/h= 375 gigawatt of power before they stop making a profit. Now compare that to global electricity use, which is on the order of 20,000 TWh/year or about 2000 gigawatt. Bitcoin miners would be using on the order of 20% of all electricity! Except that at those consumption levels, they would start driving up electricity prices, which brings me to my point: will governments really allow everybody's electricity bill to rise significantly because it is profitable for bitcoin miners? I think not.