> If you care about the environment even a little bit (like turning off lights in rooms you're not occupying) then you will reject Web3. Even the most efficient blockchains use more energy than the status quo unnecessarily.
On an Intel NUC (Core i3, low power mode) I'm running a non-mining Ethereum 1 full node[1] plus a staking Ethereum 2 node[2] (comprising two active validators) on mainnet. Measured with a Kill A Watt[3] since genesis of the beacon chain, it's using approximately USD 140 kWh of electricity per year (about USD $15/year where I live), and makes use of the Internet connection that I use for everything else personal and work related. The Ethereum 1 node also acts as my personal gateway to Ethereum vs. say my needing to connect through Infura.
There are today 279235 active validators[4] on Ethereum's mainnet beacon chain. Now, I know that Ethereum hasn't made the switch over to Proof of Stake yet (that's what Eth 2 is all about) but it's coming this year. Let's ignore the kWh usage of my non-mining full Eth 1 node and assume the 140 kWh is split evenly by the validators (it's not even close, the Eth 1 node is a pig in comparison, but for sake of argument), then round each one up to 100 kWH per year and assume that's the average per validator going forward, and let's grow the beacon chain to 1 million active validators. So that's 100k MWh per year. Amazon reported[5] that they consumed 24 million MWh in 2020.
I'm not sure how many combined MWh are consumed by the data centers for VISA, traditional banks, etc., but I'm guessing it's nothing to sneeze at. According to Statista[6], it costs about 150 kWh for VISA to process 100k transactions. According to VISA[7] they processed about 206 billion transactions over 12 months. So that's about 309k MWh.
A couple of things to consider also. Ethereum devs are concerned about energy consumption, and there are active efforts to drive down the energy cost per validator by the various projects (nimbus, teku, etc.). Also, my Core i3 Intel NUC is pretty heavy-duty compared to lower-end hardware capable of running a validator node. So I expect the energy cost/year of Eth 2 to improve in coming years.
[1] https://geth.ethereum.org/
[2] https://github.com/status-im/nimbus-eth2#readme
[3] https://en.wikipedia.org/wiki/Kill_A_Watt
[4] https://beaconscan.com/
[5] https://sustainability.aboutamazon.com/environment/sustainab...
[6] https://www.statista.com/statistics/1265891/ethereum-energy-...
[7] https://usa.visa.com/dam/VCOM/global/about-visa/documents/ab...