Watts or Lumens?
With conventional light bulbs we used to choose the bulb by the Wattage. This is because there is little or no variation in the light output from old bulbs. For example - a 60w bulb always produced the same amount of light - around 800 lumens.
Lumens have come into everyday use largely as a result of the government mandate to phase out incandescent light bulbs in favour of CFL and LED bulbs. Because the old and new types of bulb consume very different amounts of energy to produce a given amount of light, lumens offer an easier way for consumers to compare the new LED lightbulbs with the old ones they are replacing.
The chart gives the approximate amount of lumens produced by conventional incandescent light bulbs.
LED lighting technology is constantly evolving, light bulbs are getting ever more efficient and we are getting higher lumens outputs for each watt of energy consumed. it is not accurate to simply state a 7w LED bulb is a direct replacement for an old 40w bulb, for example. It depends on the bulb. We need to look at the lumen output.