In 2007 former president George W. Bush signed the Energy Independence and Security Act (EISA) into law. The provisions in this law are intended to reduce energy usage and greenhouse gas emissions and enable the US to be less dependent on foreign sources of oil. It's a rather sweeping set of changes, but the change most relevant to consumers is probably the phaseout of 40W, 60W, 75W, and 100W standard incandescent light bulbs.
The EISA provides for a three year phaseout schedule that starts with inefficient 100W incandescents in 2012. The next year will see 75W incandescents gone, and the third year will phase out 60W and 40W bulbs. In addition to the phaseout, the law sets minimum standards for general service incandescent light bulbs, making it necessary for you to replace old inefficient incandescents with new energy efficient lighting.
There are three technology options for replacing incandescent light bulbs; halogen, compact fluorescent, and solid state (LED). New halogen light bulbs
will be in wattages compliant with new maximum rated wattages. The new wattages replace the old as follows; instead of 40W, 60W, 75W, and 100W, maximum rated wattages will be 29W, 43W, 53W, and 72W. You can expect new halogen bulbs to be designed to look just like old incandescents, and because halogens are a form of incandescent light bulb you can use them in any place you're currently using incandescents.
The other two energy efficient options (CFL and LED) use a lot less energy than even halogens, but have drawbacks of their own. Compact fluorescent light bulbs
are very energy efficient and come in nearly any color temperature you could want, but they do contain very small amounts of toxic mercury so they must be handled with care and disposed of/recycled carefully. LED light bulbs
do not contain mercury, but are currently extremely expensive, limiting their use to commercial and business applications for now.