The GU24 socket and base system is designed to replace the Edison socket and base in energy efficient lighting fixtures.  The ENERGY STAR® Program Requirements for Residential Lighting Fixtures, Version 4.0 require that residential lighting fixtures cannot use the standard Edison screw base, even if they do not have a built-in ballast.  The same requirement is included in California's Energy Efficiency Standards for Residential and Nonresidential Buildings, known as Title 24-2005.  This requirement is designed to insure that fixtures that receive ENERGY STAR® qualification when using an energy-efficient self-ballasted CFL, or are qualified as energy-efficient under Title 24-2005 cannot be operated with an incandescent lamp. 

Beginning August 2008, the ENERGY STAR technical specification (v4.1) will be expanded to include lamps that work with GU-24 bases. These bases differ from traditional screw-in sockets in that they offer a simpler twist-and-click method of installation or removal. The major benefit of this new interface is that any fixture with a GU-24 socket will work with any bulb having a GU-24 connection. This means that the wattage, color temperature, and style can be controlled and varied by the user, rather than being limited to the particular setting it was initially sold with. This is a huge innovation -one that consumers have long been clamoring for, and GU-24 is expected to become the new standard for lighting both in homes and offices. In fact, today's screw-in light bulb is expected to fade from popular use in the near future, much the same way as the cassette player and rotary telephone have been replaced by more technically advanced standards.

The GU24 socket was designed to be compatible with these energy efficiency regulations.  The GU24 base has two dual-diameter pins; the smaller portion having a diameter of 3.4 mm (0.13 inches) while the larger portion has a diameter of 5 mm (0.2 inches).  [A link to a drawing of a GU24 base will be added.]  CFLs with a GU24 base are designed to be connected directly to the power line, so they are functionally equivalent to screw-base CFLs instead of normal pin-base CFLs.  Unfortunately, ENERGY STAR® refers to CFLs with the GU24 base as self-ballasted pin base lamps, a designation that may lead to confusion with pin-base CFLs that do not have an integral ballast.  Some manufacturers are also making modular ballasts with a GU24 base on one end and a socket for a normal pin-base CFL on the other.  These modular ballasts can be used to adapt normal pin-base CFLs to fixtures that have the GU24 socket, thereby reducing the amount of material that must be thrown away when the lamp fails.

Another big advantage of the GU-24 standard is that the lamp and ballast are always housed in the same unit. While slightly more costly to produce, this is more than overcome by their increased convenience and simplicity of maintenance. The savings become even more pronounced where lighting requirements are greater and more stringent, such as in large commercial facilities.