Contrary to rumor, the incandescent lightbulb is not going away--at least not right away. New U.S. regulations, starting January 1, cap energy consumption of a roughly 1,600-lumen bulb (equivalent to a standard 100-watt incandescent bulb) at 72 watts--which means the workhorse of home lighting will have to become about 30 percent more efficient overnight. The law will expand in the next two years to cover 75-, 60- and 40-watt bulbs. There is room for improvement: incandescent bulbs currently waste 90 percent of their energy as heat. Halogen incandescents provide a more efficient, if pricier, alternative and will give compact fluorescents a run for their money. A light-emitting-diode replacement for 100-watt bulbs is expected to reach market this year; dimmer LEDs are already available. Consumers will be able to check federally mandated labels that give performance specs, similar to nutrition labels on food, but here we illuminate the essential facts.