Furnace 4

Lore & Background

In the sprawling, rust-and-concrete world of Factorio, smelting ore into metal is the backbone of every factory. Players begin at the Stone Furnace, a squat grey block that clanks and spits out iron plates while consuming coal. As the factory grows and the player's research tree deepens, the Steel Furnace replaces it—faster, sturdier, and visually heavier, its dark iron casing a small monument to the player's first real industrial milestone. The Electric Furnace crowns the progression. It draws power from the grid, eliminates fuel logistics, and smelts at a rate that lets the player finally stop babysitting coal belts. For most players, that is the end of the smelting story. The game's research tree offers no further furnace node, no 'Furnace 4' technology, no hidden recipe. The Electric Furnace is the apex. Modders have built nuclear-smelted, laser-heated, and even quantum-entangled furnaces. Speedrun communities joke about a 'Furnace 4' as a speedrun-tier unlock that doesn't exist. The desire is real; the item is not.

In Their Own Story

The player crouched beside the Electric Furnace, watching its blue glow pulse in rhythm with the power grid. Forty-three of them lined the smelting hall, each one humming, each one spitting out copper plates in a steady, satisfying stream. It was enough. It had to be enough. They pulled up the research menu one more time, scrolling past the last technologies—Robotics, Space Capsule, the final nodes. No fourth furnace. No 'Plasma Smelter.' No 'Furnace 4.' Just the same three boxes they'd been staring at since the first hour, when a single Stone Furnace and a handful of coal felt like the summit of human achievement. They closed the menu. Picked up a coal pickup. Walked back to the mine. The factory hummed on, and the third furnace was enough. It had always been enough.

Reader's Guide

Because 'Furnace 4' is not a real technology or blueprint in Factorio, there is no research cost, prerequisite chain, or unlock to document. What *does* exist is a three-step smelting progression that every player walks through:

**Stone Furnace** is available from the start (no research needed). It smelts at 0.5 items/s and requires coal as fuel. It is the default and the only option until you research further. **Steel Furnace** is unlocked by the 'Steel Furnace' technology (cost: 20 science, requires Science Pack 1). It smelts at 1.0 items/s and also requires coal. It replaces the Stone Furnace in most mid-game layouts. This is the final furnace tier in the base game. There is no fourth node. No blueprint entry for a 'Furnace 4.' If you see one referenced in a mod, community map, or fan wiki, it is either a modded addition or a mislabel. The base game's smelting ceiling is the Electric Furnace, full stop. Plan your factory around that constraint, and the rest of the tech tree will make sense.

Did You Know?

• The Steel Furnace and Electric Furnace both smelt at 1.0 items/s; the Electric Furnace's advantage is eliminating fuel logistics, not raw speed.
• The Stone Furnace is the only furnace that can be placed without any research, making it the very first machine most players ever build.
• No official Factorio update (from 1.0 through 2.0) has added, hinted at, or referenced a fourth furnace tier.