Going to go out on a limb here and predict credit cards have a better $/watt ratio than bitcoin.
https://motherboard.vice.com/en_us/article/ypkp3y/bitcoin-is...
Further, the cost per transaction in bitcoin a year from now will be about 1,000,000 times lower due to Lightening Network.
I know there's a political desire to demonize bitcoin (this is vice, not exactly an objective source) and that ignoring one side of the equation to try and make bitcoin out to be an environmental evil seems the best approach you can get but its' absurd on its face.