If you have a bunch of incandescent bulbs you think you should use up before replacing them with LED, think again. Those old bulbs are not worth the electricity they’ll use, so dump ’em. Unlike compact fluorescent (CFL) bulbs, they don’t contain hazardous materials. The bulb materials are so low in value that recycling doesn’t help.
One 60-watt incandescent bulb, in a typical 1,000-hour life span, would be responsible for emitting more than 40 pounds of carbon dioxide. And one would emit as much as 90 pounds in places that rely more heavily on coal to generate electricity. An LED producing about the same amount of light emits only a fourth as much CO2 and would be responsible for about just 10 pounds.
Cost-wise, incandescents burn out before you turn ’em on.