EPA recommends only using qualified CFLs that are specifically designed for 3-way sockets. In order for an ENERGY STAR qualified CFL to work properly on a 3-way socket fixture, the electrical connections and ballast circuitry must be designed to allow the lamp to light at 3 distinct light levels. Even if you are only using the lamp at the highest level, to ensure optimal product quality we recommend using a 3-way ENERGY STAR qualified CFL. To find a list of them, go to our CFL Advanced Search, and choose "3-way" under "Specialty Products.
Manufacturers are trying to make it easier for consumers by labeling their products with special features or lack there of, on the front of the packaging as well as in the fine print. Please keep in mind that due to the special technology required, three-way bulbs tend to be a bit more expensive than regular CFLs.