Ed Fredkin explained it to me this way, "If computation took energy, how could the Universe compute its future?"
The thing is, computation doesn't "take" energy. In fact, one could argue energy doesn't exist in the first place, it's just an abstract concept we introduced to describe some sort of equivalence between different physical phenomena. Thanks to Einstein, we can say that x amount of mass somehow 'equals' y amount of photons or z amount of heat. This equivalence is expressed in terms of energy, measured in Joules, but saying these things are all different forms of energy is mostly an abstraction.
Hence, computing the future doesn't "take" energy, but rather converts a few tiny physical objects or phenomena into others. Just like a combustion engine doesn't "take" energy but merely converts fuel into gases, heat and motion. Similarly, the universe will (verrrrrry slowly) convert itself to a homogenous mixture of low-energy-density gases and radiation, while continuously computing its own future.