Minecraft wiki entry for Experience_farming, associated text: For large smelter farms, the load can be divided among several furnaces, which can be harvested separately; list allows storing larger amounts of experience without needing to harvest it all at once, and also allows faster progress (so long as the input farm can keep up). For a simple single-furnace setup, nearly two stacks of cactus (120 items) can be burned in a Minecraft day, collecting 360 XP per real-time hour. Potatoes and kelp burn twice as fast, but give less experience, yielding respectively 252 and 72 XP/hour. Of course, maintaining this rate for long periods of time requires an input farm large enough to supply 120 or 240 items per day, and this will be multiplied for multi-furnace setups.