been wondering that as well, how scrypt compares with SHA-256 in terms of processing, thus electric consumption, once a critical mass of coins are mined. figured scrypt was more energy-intensive in toto, but 10,000x? can you be so kind to share some verification of that, for us lowly BSICs?
one important factor to consider as well is that scrypts are limited to GPUs, thus limiting the processor “arms race” (as satoshi aptly described) & continuing hardware obsolescence. thus, the energy consumption (and blockchain security) will be distributed across a much wider net with scrypt vs. SHA.
this will also allow for greater innovation in capturing and reusing the waste heat for personal use, which is 90% of the electricity use. freedogger already came up with an ingenious solution to heat his home from his mining rig over the weekend.
other factors to consider would be : residential vs. commercial rates, and global arbitrage of power costs.