I doubt wheat is the most energy efficient plant. I'd guess it's actually pretty poor, although it may be one of the best in terms of us eating it. That said,

I doubt wheat is the most energy efficient plant. I'd guess it's actually pretty poor, although it may be one of the best in terms of us eating it. That said, you tend to lose a ton of efficiency if you grow a plant, cut it down, process it, and then eat it. That plant is doing a lot of things other than making you food. If you are producing your energy straight from the sun, you'd do this a lot better. I'd say you could get away with far less than your estimate.