# kilowatt-hours per transaction
  # https://motherboard.vice.com/en_us/article/ywbbpm/bitcoin-mining-electricity-consumption-ethereum-energy-climate-change
  btc = 215 

  # Transactions per day
  tpd = 3e5

  # convert btu to terawatt-hours
  # http://www.dvirc.org/how-much-energy-does-an-office-building-consume/
  officeEnergyPerYear = 1.4e9*.293071/10^12

  # https://www.usatoday.com/story/money/business/2014/10/05/24-7-wall-st-banks-with-most-branches/16648133/
  nBankBranchUS = 94725

  # Convert to kw-h to tw-h
  btcEnergyPerYear = btc*tpd*365/10^9

  >   btcEnergyPerYear/(officeEnergyPerYear*nBankBranchUS)
  [1] 0.6057412

I have no idea if the source numbers are correct, but this is a better statistic. Mining uses the same amount of energy as used for ~58k average office buildings. So the worldwide bitcoin mining energy consumption is about half of that currently used for banks only in the US. This is assuming banks are "average" (probably higher due to security concerns) and of course that banking doesn't consume energy in any other way.