4 watts! By design, this old bulb produces at least 10 times less light than an average modern one. The key reason for that is the limitation imposed by the low-current DC electricity distribution system invented by Edison. His main business constraint was the cost of copper wires: the higher the current, the thicker and more expensive the wires would have to be to feed the bulbs. But expensive wires would not allow Edison's system to cover a large city area, making it a poor competitor for gas lighting installations popular at the time.
Therefore, Edison settled on a low-current system, which required high-resistance light bulb filaments. Unfortunately, a carbon-based filament found by Edison, the famous bamboo one prominently shown in books and movies, would heat up during operation and burn out fairly quickly. Furthermore, the carbon filament would eventually blacken the inside surface of the bulb, turning it even dimmer. To make his system more reliable, Edison had to limit the brightness of bulbs used, the bulbs bright enough to beat competition from candles, kerosene and gas lamps. Only with the invention of high-resistance tungsten filaments by Hungarian engineers in the beginning of the 20th century and, later, the process of filling the bulb with an inert gas, light bulbs began approaching levels of brightness comparable to today's standards.
Eventually, the world created highly resistant bright light bulbs that consumed more and more electricity, the electricity coming over long transmission lines from distant power plants burning fossil fuels, losing lots of power on the way and in the bulb itself because most of the power went into heat. Paradoxically, with low-power LEDs and local solar panels producing low-current DC we don't need the heat and the transmission lines, but we still lack efficient power storage systems. When these are deployed at scale, we'll go back to Edison's good old idea of a 4-watt bulb, which, implemented with new technologies, will shine brighter and greener(!) than ever before.
tags: system, evolution, power, distribution, tool, constraint, trade-off, payload, course