[burroisolator]

I don't think they do if you're just referring to how difficult it is to pull off a 51% attack. Assume the status quo is that it costs X to secure 51% of the hash power. If there is a new ASIC that can hash twice as fast with the same energy use, then suddenly it will cost 0.5X to secure 51% of the hash power. But if the price of Bitcoin remains the same, then miners will have an incentive to double their hash power as that was their breakeven point before. And so now you've gone back to the previous status quo. Assuming the attackers have access to the new ASICs, it still costs X to 51% attack the network.

[cinntaile]

I'm not sure I understand your reasoning regarding the price of bitcoin staying the same and the miners having an incentive to double their hashpower. In the situation you described, you'd have the same hashing power but half the energy cost? Doubling it would double their hashing power and keep the energy cost the same. I don't see how this doesn't lead to a more secure network?

I don't think you can neglect the price of a new ASIC in a real situation though, those things are very expensive. Where it was first possible to attack the network using regular hardware, it now requires a much bigger capital investment. When ASICs were first released they had a bigger advantage than they have now, it seems unlikely a 2x improvement over the previous generation is still possible (assuming it was possible before, I didn't check).

[burroisolator]

It doesn't lead to a more secure network because the costs to attack the network are the same. Attackers will have access to the same technology and have similar costs.

Right, I'm not saying there will be a new ASIC; just that there will be no innovation in the Bitcoin space (unless they switch out of PoW) that leads to less energy being used.

[cinntaile]

I agree with that, it seems very unlikely we'll go to a less energy situation unless a price decline happens. At least until all bitcoins have been dug out.