I read somewhere that both a closed and a finite flat universe would have zero total energy in General Relativity (On the Zero-Energy Universe). But the best evidence shows that the universe is flat and infinite: "We now know (as of 2013) that the universe is flat with only a 0.4% margin of error. This suggests that the Universe is infinite in extent" (NASA).
In this video, at 1:09:59, Lawrence Krauss says: "[Inflation] tells us, remember, that in the largest scales the universe isn't flat. It's actually closed." But the whole point of his argument is that the universe is flat and, because of that, its total energy is exactly zero (e.g., from 53:32 to 54:23).
So, I'm confused. Does inflation really predict a closed universe? If so, how is that compatible with the evidence that the universe is flat?