The energy expended is the security of the currency. If a transaction is confirmed by 1 TWh of proof of work, that much energy is required to alter it, meanwhi

The energy expended is the security of the currency. If a transaction is confirmed by 1 TWh of proof of work, that much energy is required to alter it, meanwhile the bitcoin network has expended even more energy. It is still young, and the exponential growth in energy consumption is going to stop as an equilibrium is reached.