http://ttevhjjsjxz6uqqcjkbig5cycd7n7xv7cmd6f5fcvrqaaa7f3bj36wad.onion/technology/security/pow/index.html
With the PoW protection, the energy savings happens because of the attacks that
did not happen, or stopped early, because the attacker realized they were too
expensive to perform, and are not actually preventing access. For more information: See discussion in this thread See Section Environment of the current specification Could we have a rough estimate on the energy spent during an attack, even if just speculative?