Running a T-account in Excel is even more energy-efficient.

A recent report "Energy Footprint of Blockchain Consensus Mechanisms Beyond Proof-of-Work" (http://blockchain.cs.ucl.ac.uk/wp-content/uploads/2021/09/UC...) has estimated (Table VI) the energy consumed per transaction of leading proof-of-stake and found that some exceed the efficiency of VisaNet (including Eth 2.0 on a high-throughput projection):

  Platform | Per transaction (kW h/tx)
  Eth. 2.0 |   0.00009 – 0.00286 (High throughput projection)
  Eth. 2.0 |   0.01823 – 0.55713 (Low throughput projection)
  Algorand |   0.00017 – 0.00534
  Cardano  |   0.01239 – 0.37854
  Polkadot |   0.00378 – 0.11556
  Tezos    |   0.00036 – 0.01096
  Bitcoin  | 360.39300 – 3691.40700
  VisaNet  |   0.00358