Some n amount is not required. Energy usage varies based on how many miners are running. It is a form of Sybil resistance, which may be understood better by rea

Some n amount is not required. Energy usage varies based on how many miners are running. It is a form of Sybil resistance, which may be understood better by reading white paper. Mentioned elsewhere in this thread is the LN network which is cheap, fast, and low energy. LN allows spending coin pegged off the main chain.