no, because there's a lot the CPU does that is neither decoding nor execution. There's also caches, register renaming, branch prediction, inter core communication for atomics, and a dozen other things.

Sorry poor terminology use on my part. I mean more broadly that most energy is used on frontend and middle end, rather than backend and that this is what vectorisation improves in regards to energy consumption. Register renaming and branch prediction energy consumption should be improved in the same factor as decoding. Caching probably less so (depending if we are talking instruction, data or combined).

I don’t think inter-core communication is too relevant when comparing vectored and non-vectored on a single core, but definitely would be when batching across multiple cores.