So many people have an opinion, but nobody is doing the calculation. I'll give a helping hand: an Antminer S9 can do 13TH/sec, and uses 1.2 kilowatt, if it runs one hour, it uses 1 kwh. I multiply this with 24 (for the day) and 365 (for the year). This is a bit less than 10'000 kwh.
Now I am looking at bitcoin.info, in the charts, how many terahashes are approximatly used. As of today (2018march05) I read 23mio TH/sec. I divide this 23mio TH/sec by the power of a single Antminer, to get an idea how many there might be in the world. This gives me 1.77mio Antminers. They consume all together per year 1.77mio * 10.000 = 17'700'000'000 kwh. Divided by 1000 for megawatthours, and another 1000 for gigawatthours and another 1000 for terawatt hours. 17,7 Terawatthours per year (well, it is growing at an enourmous speed...).
How many power supply units does this make? A huge carbon plant or atomic system provides 1000 Megawatt, equivalent to 350 wind turbines. 1.77 mio Antminers consume roughly (1.77mio * 1.2 kw) 2.124 Megawatt. This means, on the other side of the power plug must be roughly two atomic or carbon power plants.
Wikipedia says, that there are 3mio ATMs worldwide. I found different sources for ATM power supply, and found between 125Watts and 750 Watts. So lets only work with 125 Watts. This is 0.125 kW times 3mio installed systems gives me 375 Megawatts. So only the ATMs consume roughly one third of the Bitcoin miners.
I think this gives a good relation, and now the experts can extend this with the amount of power for printing dollars, distributing dollars, office space of the employees, transportation costs of the employees, and much much more. For sure this is still a naive comparison, cause the dollar reaches literally everyone, whereas bitcoin is still in its infancy (with constantly growing power demands).
Oh, on the power supply of Denmark: there are 5.75 mio inhabitants, and consumes per inhabitant 0.6kwh, so Denmark consumes 3450 Megawatt, which requires a bit more than three atomic or carbon power plants. But as Denmark is champion on windenergy per inhabitant, it is more like 1000 wind turbines :-) This gives an annual consumption of ~30 Terwatthours per year.