I keep hearing this repeated in threads about Bitcoin, and it's just flat out wrong. Bitcoin's energy usage does not scale based on the number of transactions. Its energy usage scales based upon the value of the block reward and the efficiency of mining operations.
It's not wrong. Bitcoin's energy usage does scale based on usage; it scales based on the value of money flowing through the system (in order to secure a certain transaction volume, you need electricity usage that corresponds to the value of those transactions). In order for Bitcoin to replace banks, it would have to consume an incredible amount of electricity.
If the electricity usage falls below a certain fraction of the value going through the network then double spending attacks become a significant risk. Bitcoin only works on the assumption that the electricity usage (and hardware usage) is too high to make double spending attacks feasible.
