Would you say that the worldwide electricity consumption of Christmas decorative lights (2.3 GW assuming it's 3× the US) is "astounding"? Well, Bitcoin miners consume less than that: I estimate 1.7 GW based on my previous research bounding it to 0.6-1.2 GW as of July.
http://blog.zorinaq.com/bitcoin-electricity-consumption
Why do miners receive such a disproportionate amount of criticism considering that so many other energy uses are vastly more wasteful by multiple orders of magnitudes... Cars alone waste 95% of their fuel energy. The US wastes 61-86% of its energy: https://cleantechnica.com/2013/08/26/us-wastes-61-86-of-its-... But, no, the average HN reader seems more concerned by these miners using 0.01% of the world's energy.
In the future, we may eventually reach a point where the energy use starts becoming worrying, but we are currently very far from that point.