For a full picture, however, you would need to count the total number of VISA transactions and compare that to the total number of Bitcoin transactions. I would

For a full picture, however, you would need to count the total number of VISA transactions and compare that to the total number of Bitcoin transactions. I would guess the absolute energy foot print of VISA is still considerably larger. But I am not trying to defend the energy usage of PoW, here. A single Bitcoin block can only fit about 3500 transactions and all miners of the world compete for being the first in solving the emerging Block‘s cryptographic puzzle. This is where the insane energy consumption comes from. Other cryptos work differently in that respect and, hence, are way cheaper.