Incandescent bulbs are labeled and classified by their electricity consumption. It's literally in the product description: 40W bulb, 60W bulb, 100W bulb, etc.
Cost is based on both consumption and efficiency, not consumption alone because with a more efficient bulb you can illuminate a given area with fewer bulbs.
The cartel disbanded in 1939. Were the bulbs labeled and classified by power consumption before then?
you need to know watts and lumens. It's not rocket science.