Comments between Sean Carroll and David Palmer are the real meat here.

- In the Many-Worlds formulation of quantum mechanics, the energy of the wave function of the universe is perfectly conserved. It doesn’t “require energy to make new universes,” so that is not a respectable objection to Many-Worlds.

- In any formulation of quantum mechanics, energy doesn’t appear to be conserved as seen by actual observers performing quantum measurements. This is a not-very-hard-to-see aspect of quantum mechanics, which nevertheless hasn’t received a great deal of attention in the literature. It is a phenomenon that should be experimentally observable, although as far as I know it hasn’t yet been; we propose a simple experiment to do so.

The first point here is well-accepted and completely obvious to anyone who understands Many-Worlds. The second is much less well-known, and it’s what Jackie and I wrote about. I’m going to try to make this post accessible to folks who don’t know QM, but sometimes it’s hard to make sense without letting the math be the math.

In kind, I'll say that Many-Worlds Interpretation is on the peripheries of what I do, so this post was conceptually difficult, alien even. I will, however, repeat the mantra of my numerous mentors: if your theory doesn't obey experimental results, you most likely didn't bother modelling/thinking exhaustively. It is, pretty much, my default uneducated stance.

As a bonus, here is a formidable article exploring more fundamental take on conservation laws in QM.