Thermal efficiency is an absolute - units of energy expended vs work achieved. There is an alternative: proof of stake. Or removing certain constraints on the problem space. A different approach to solving the problem is absolutely an alternative. Visa is an alternative. The extant banking system is an alternative.

You can't say how efficient it is without calculating how layer 2 scaling affects per transaction energy usage. You can do millions of layer 2 transactions that eventually settle as 1 transaction on the main chain.

You can do “layer 2” transactions that settle on ACH or wire transfers, like Venmo or square cash, what’s your point? This is just more shameful greenwashing to pump up bag.

You would have to do literally millions per on chain transaction using bitcoin to match ACH, visa or a proof of stake chain.

This is of course after you consider opening a single LN channel for every human on earth would take 75 years and 300 billion dollars if the chain did nothing else. Like putting in a request for a Soviet phone line. LN has quadratic routing efficiency and is boat anchored to garbage.