For kicks I wanted to see how viable a self-sustaining power generator could be using a cobblestone generator.
A block-breaker is used to pull a cobblestone block and spit it out in to an obsidian pipe. The redstone timer is tweaked to 1.5s from the default of 2s and this matches the cobblestone generation perfectly.
The obsidian pipe feeds to a gold pipe and then in to the top of a Recycler. The gold pipe is used to expel cobblestone when the recycler fills up and sends it to the lava block.
A pipe from the recycler (powered by redstone pump) sends scrap to the input of a generator. The generator powers the batbox and the recycler draws its power from the batbox.
The system has to be primed - so at 0EUs a single piece of coal in the generator is enough to get it going.
The third image shows a setup of 4 such generators. I had fun doing it.