Can you list your assumptions? For starters, are you assuming constant power production and constant power price? Because neither of those will hold whatsoever on the timescales you're talking about.
It is not a perfect model by any means that is why I called it "rough 'back of the envelope' estimates" . All values static and based on "today's" numbers:
https://bitcointalk.org/index.php?topic=694401.0The rising worldwide power production will "help" us use a lower percentage of the overall power production.
The rising cost of power will "help" us use less power.
The hidden assumption that everything except electricity is free causes this model to overestimate energy consumption by at least a factor of 3-4 if not more based on current costs. The fixed costs in mining are way too high to justify electricity consumption alone as the criteria for profitability. While it's true that an existing operation with money already sunk in capital expenditures is going to be closer to the assumption of this model as far as the cutoff point to stop operating specific equipment, the bitcoin price has to plausibly cover fixed costs for a new operation and not just electricity. In the realm of even just hobbyist basement type setups, it's almost inconceivable that mining equipment would ever even come close to energy cost - equipment cost parity over its entire marginally-profitable lifetime, until some point in the non-foreseeable future where improvements in equipment efficiency radically stagnate.
All true. So divide the power consumption by your favorite factor.