So I was looking at this mod for a modded playthrough. I immediately noticed coal as a possible replicable item! It seems silly to spend 0.64 MJ of energy to produce 4 MJ of power via energy -> coal -> boiler -> energy. And the uranium conversion is much better!

Some math ( https://www.reddit.com/r/factorio/comments/6a05i8/math_how_much_energy_does_uranium_ore_produce/ ) shows uranium to be roughly 1000x more energy dense than coal. And this is to say nothing of solar. But to prevent getting too out of hand with coal or uranium, the simple replicator ought to consume 1.6 MW of power and uranium ore should take approximately 2500 seconds per unit produced rather than 18s. And this isn't even accounting for the effect of efficiency modules. I can change the base cost of the recipe via settings, but I can't change the time for uranium ore.

Anyway, just some thoughts on balancing. The idea of adding a method to use surplus solar power is neat, but it seems too easy.

Given the lore around the mod, that you're pulling dark matter into the normal matter universe, in theory, all ore should have the same cost per unit mass. I believe the ordering should be roughly coal, copper, iron and uranium ore in order of how much mass one unit of ore represents; given all ores have the same stack size, presumably it's the same volume of ore per chunk, thus the mass would differ. On the other hand, in theory, given the energy content of uranium ore, it should be feasible to calculate the mass of a chunk of uranium ore, the same way that a chunk of coal's mass was calculated.

If there wasn't a net energy gain from replicating coal or uranium ore, why would you bother? If you've got a big solar farm that you're sinking the extra production of, replicating coal to produce plastic might be interesting... but you have no coal power station, so you have plenty of coal; you could replicate uranium ore to produce uranium ammunition, I suppose.