The Problem
Incandescent light bulbs were first invented in 1879. While they're inexpensive to purchase, they use a high amount of wattage, and don't last long (typically less than 1,000 hours). Under federal law sales of incandescent bulbs will be prohibited except in specialized applications in 2012.
Halogen lights last longer (up to 3,500 hours) then incandescents and compact fluorescent lights (CFLs). However, they're more expensive and use more wattage.
Fluorescent and compact fluorescents are the most widely available efficient light sources, though light-emitted diodes (LED) that use 10% of the electricity of incandescent are available for exit signs and other applications, and will likely to widely available for other applications within the next three years. CFLs last longer than incandescents and halogen bulbs (typically 10,000 hours) and use less energy. They cost more initially, though bulb prices are often low due to public sector subsidies, and over time they save money.
Below is a cost comparison for incandescent and halogen light bulbs:
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