How many CPU's work on blockchain today? How many CPU's are working on blockchain now?
How much energy is estimated to be consumed?
I read an article on coindesk saying it may surpass all other energy consumption by 2020..... seriously?
I last recently did this calculation: 
An Antminer S9 uses 1,2kW power, which is 1,2 KiloWattHours (kWh). If we multiply with 24 and with 365 I get around 1000kwh. At Blockchain.info there was end of November 10,445,729,472 GH/s, or 10’445’729 TH/s. Divided by the power of an Antminer S9 with 13 TH/s, I’d need 800’000 Antminer S9. They would consume 10’000 KWh, and if I need 800’000, I get 8’000’000’000 KWh, which is  8’000’000 MWh (Mega Watt hours), is 8’000 GWh (Giga Watt hours). Not all are using S9, so it might be a bit higher...

Compare this to a water cooker, or a hair dryer, which uses 2kw. Instead of making tea, or drying your hairs, consider mining a bit!

In summary this means, on the other side of the power plug must be a power system which can supply ~1000 MegaWatts. This is the range of large industrial systems like carbon or atomic power supplies. Or even better, 500 wind power turbines at 2MW. 

I cannot predict the future in 2020, but this would be a bit too much...