Satoshi got this part wrong.
What if bitcoin were still around $1 - $2 which is probably what satoshi was expecting. Then, there'd be no ASICs, or only small ones. Just thousands of BlockErupters each costing $100. It'd take almost forever to ROI. Nobody would develop 14um - way too expensive. This would have been ideal.
But, bitcoin got WAY too popular too fast. This means miners rushed to increase hash rate. mining capacity went WAY up.
This is how much the network consumes - precisely - and unambiguously It is the average cost of electricity for all regions where mining is done, divided by the current reward rate (ie 25BTC soon to be 12.5).
Just like sardines in the ocean. The number of them depends precisely on the food available. The population will grow with great efficiency until the food supply will be fully consumed.
The mining capacity will grow with great efficiency until nearly every penny is spent on electricity and the margin is tiny. 12.5BTC/10min is the food supply. 06 cents/kilowatt hour is the cost of electricity. Therefore, the network will spend precisely $31,500 (6*12.5*$420) per hour buying electricity (presently (6*25*$420). Mining profits are negligible - and always will be - because crazy fuckers will buy more machines the instant the margin rises slightly above zero. 100% of the reward rate is going to electricity. (actually, miners have some other expenses too but we can just ignore them as small in comparison).
Because the average cost for electricity is probably about $.05 or $.06/kWhr perhaps, the network uses (after the halfing): 525,000 kWatts! ($31,500/.06). About 500 Megawatts is the network consumption for the next coming four years. No amount of adjustment or efficiency improvements can change that. It is as fixed as the reward rate of 12.5BTC/10 minutes* (the food supply) (*assumes electricity rate average doesn't appreciably move from about $.06/kwhr).
[But what if the sardines are smaller? What if they are Japanese sardines. Doesn't matter. None of that matters. Sardine breeding efficiency guarantees that the population will grow until it precisely consumes the food supply]
Bitcoin mining is the same. It will very efficiently grow to meet precisely the food supply of 12.5BTC/block
WOW! Bitcoin network burns 500 Megawatts just to stay alive.
The interesting thing is that this is a kind of 'tax' on the system. It embodies itself as inflation. New money comes into the network and gets burned off as payments to electricity suppliers at a rate of $31,500/hour. Truth is, Bitcoin today is a VERY leaky system as a ton of value is being burned off by energizing guessing machines. Yet, more suckers at a rate of $31,500 come every hour to join the herd. The rest of bitcoin holders suffer this amount of 'dilution' as more units are in the network each block. The good news, this stops in 2140. Then, we'll pay for electricity purely with fees - but there will be zero inflation.