I've started trying to make more complicated stuff in larger batches, so I've been paying more attention to the energy use, and I noticed that secret sauce and tangy sauce seem to actually use only about half the energy that it says they will when in the cooking interface - the interface said I would need 60 energy to make the 12 secret sauces, and 120 energy to make the 12 tangy sauces, but this is what actually happened:
http://dl.dropbox.com/u/8644666/Miscellaneous/halfenergy.png
(Is there a way to embed images here?)
I kind of remember the sweet and sour sauce requiring more energy, too, but I wasn't paying as close attention because it wouldn't have been an issue.