This is a great video to watch from Aurora Lighting and get the basics.
It explains that before LED lighting we relied on the wattage to determine the brightness or output of a lamp which is no longer the rule as we now look at both Wattage and Lumens which is the measurement of light output.
Why ? because in the good old days every 100w lamp gave out the same lumen output ( give or take ) but now particularly with LED one 5w lamp may give 150Lumens and another 5w may give 400Lumens depending how good the lamp really is.
Let us know what you think.