Board Thread:Questions and Answers/@comment-76.121.146.94-20130404023925/@comment-5627887-20130528195513

There's not a lot of wiggle room really, the only choice you have is between using 5 iron + normal furnace or 8 iron to make the iron furnaces (clearly you choose to use normal furnace + 5 iron to save on total iron used, cobblestone is effectively infinite as far as you're concerned). Other than that I guess it's more efficient to craft all of one type of item at a time, so make 64 furnaces, turn them all into iron furnaces, then all the batteries, then generators, etc etc etc.