Planet Of Evil

This story has been accused a couple of times of being a rip off of Planet of Evil. While I can see a couple of similar plot strands it has never particularly struck me as a blatent rip off. If anything I would call it a homage, but that's about it. I think it mainly centres around the stealing of energy and the possession/altering of the humans but the main bulk of the stories are different enough that they don't feel like copies. What do you think? Ripoff, coincidence or knowing homage to Planet of Evil?