But how much energy does a bank serving as many customers as bitcoin consumes?

 Paypal does 200 transactions per second, Bitcoin does 3. I doubt that Paypal consumes as much energy as Switzerland.
 Here you can find a study (2016)[1] about non cash payments with numbers (see the Key Finding part).
 That's the right question, how much energy does the current financial system use, solely for our "basic" transactional needs (store/retrieve/send payments).Did anyone come up with an estimate?
 Back of an envelope maths:bitcoin does some ~450k transactions/day [1]Switzerland has some 8.5m people [2]Letâ€™s assume bitcoin is only used in Switzerland, meaning we get some 0.05 transaction per person per day, or in other words every citizen of Switzerland may execute one transaction every 20 days. I have no numbers for how many financial transaction swiss people perform per day, but lets use a conservative estimate of one per day (think of the daily coffee paid by cc), so that there are 8.5m transactions/day handled by the swiss banks.Now, if the total energy budget of Switzerland would be going to running their banking system (which it probably does not do) it would still be 20 times as efficient as bitcoin.
 Significantly less? See: https://news.ycombinator.com/item?id=20352255

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