That's why the eventual value of bit-coin is supposed to be the value of the energy required to maintain it (because the cost of doing a transaction will be the transaction fees, which have to cover the miner spending the energy to process the transaction, but because anyone can compete in the market supply will always place the value at the cost of energy). Honestly in the long run bitcoin may be cheaper than credit cards or even cash in a pure energy sense. No matter what we do we'll have to spend energy to maintain our financial system.

* With cash we have to print and distribute cash, and move it around, and run hardware to validate it, and image scan it, and count it, and destroy it. Etc.

* Credit cards require servers, massive backups, authentication procedures, production of specialized hardware, and the same networked infrastructure as bitcoin, as well as server ops, bank managers, customer service. Etc.

* Bitcoin can use any machine, and the same internet as any other program. As chips get faster and more efficient the energy cost goes down.