1)Humans waste a lot of energy, if you've studied any biology you would know that very little energy thats taken in actually manages to get used (we organic beings are quite inefficient!!)
2) Why bother with the matrix at all, why not render all the humans involved braindead? then there would be know need for anything to keep their minds occupied.
3)If they need to conserve energy so badly, how can they afford to have those huge arcs of elctricity zapping between the towers (the ones with the human pods), those require huge amounts of power to happen.
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