Some energy numbers for breaking a post-quantum proposal, SIKEp751: https://eprint.iacr.org/2023/376 reports 11 seconds to break one key on a mass-market Intel Xeon Gold 6248R. That's a 200-watt CPU; maybe 100 watts more for MB, RAM, PS inefficiency; so about $0.0001 electricity per key.
Efficient computation of $(3^n,3^n)$-isogenies

@djb These proposals are broken so quickly that it would be a good idea IMO to put the brakes on any attempt at standardising them. But if one absolutely must standardise, then at least standardise hybrids, for crying out loud.

@sten Well, the problem with _not_ rolling anything out is that then we're not even _trying_ to deal with the quantum risk.

Hybrids (double encryption, double signatures) nicely resolve this tension: we roll out a post-quantum layer to _try_ to protect against quantum computers, while (at very low cost) keeping the existing ECC layer to reduce the damage if the post-quantum layer is broken.