Iron Furnaces calculator
All furnaces
How the furnaces compare
Every furnace in the mod smelts faster than a vanilla furnace but burns fuel at the same rate per item. A piece of coal smelts eight items in all of them, however fast they run. Speed only saves time, never fuel. The speed augment halves the smelting time but also halves what each fuel item is worth. The fuel augment does the opposite: items take a quarter longer, and every fuel item smelts twice as many.
The factory augment turns a furnace into six parallel slots that run on RF instead of fuel, and the generator augment makes it burn fuel for RF. With the blasting or smoking augment a furnace takes on those recipes, and they cook in half the time of smelting.