The historical progression in installed electric furnace smelting capacity of some 1650 calcium, chromium, manganese, nickel and silicon ferro-alloys furnaces is reviewed. Key increases in the inherent installed electrical capacity, often achieved through uprating furnaces, are identified. The existing furnaces delivering the maximum operational power input for each ferro-alloy commodity is identified. The range of applicable furnace electrical configurations (AC or DC; immersed, submerged-, shielded- or open-arc); furnace configurations (circular or rectangular; closed or open, and 1-, 3- or 6-electrodes); electrode forms (graphite, self-baking or composite), and electrode power density, as pertinent to process metallurgical requirements, are investigated. A view is presented on the prevailing state of evolution of the Mega-scale in ferro-alloy smelting and opportunities for still further improvements. Specifically it is suggested that the next era of more productive, higher capacity ferro-alloy electric smelting furnaces could require actively bound, rectangular, multi-electrode configurations, either AC six-in-line (6iL) or DC.