> Really though, the fact that every single transaction is broadcast and that every single transaction must be verified by the entire network (in theory) is wha

> Really though, the fact that every single transaction is broadcast and that every single transaction must be verified by the entire network (in theory) is what kills Bitcoin's energy efficiency. It is also the fact that ensures it's distributed nature, and the purpose of its very existence in the first place (we have plenty of centralized digital currencies). > Whenever a new mining rig is brought online, the energy efficiency of Bitcoin decreases -- and Bitcoin is designed to incentivize bringing more mining equipment online. This is not necessarily true. The efficiency (number of SHA256 operations per joule expanded) will increase over time. It has already increased by a factor of 1000 compared to CPU mining. So it's definitely possible for both the security and the energy efficiency to increase simultaneously.