Amdahl's law applies here: some things are just not worth worrying about. If you're Google or Facebook, you already have entirely selfish incentives to optimize

Amdahl's law applies here: some things are just not worth worrying about. If you're Google or Facebook, you already have entirely selfish incentives to optimize your code. If you're not, and the performance of your "inefficient" software is acceptable to you and your users, the net environmental benefit of rewriting it in C is likely indistinguishable from zero. It may even be negative, if the increased development cost prevents you from improving energy efficiency elsewhere.