Wattage is a measurement of the electricity usage of a bulb. Lumens is
a measurent of the total light output of a bulb. The efficiency of a
bulb is calculated by comparing the light output to the energy usage.
The efficiency of a bulb is similar for light bulbs of the same type,
so you can expect that by switching from a 100W to a 150W regular
incandescent bulb that you will get about 50% more light. However, If
you switch from a 60W regular incandescent bulb to a 60W halogen bulb
you may actually get more light, because halogen bulbs are more
efficient.