Why Doesn’t My Light Fixture Use a Normal Light Bulb?

GU Base Light Bulbs: Explained

Light bulbs come in many shapes and sizes and are equipped with a variety of bases. From your standard E26 Medium Screw base to a GU24 bi-pin connector, and everything in between. So, what exactly is a GU base light bulb and why does it matter? So glad you asked!

A GU24, GU10, or GU6.5 base lamp includes a bi-pin connector for LED and CFL (compact fluorescent) bulbs, which functions like a bayonet mount that installs into a compatible fixture. Using a twist-and-lock feature to secure the bulb in the socket, this is in direct contrast to the standard Edison-style screw base that is found on most traditional bulbs. You cannot use a GU base bulb in a standard screw-style socket for (what I hope are) obvious reasons. Further, the number following the GU in the base code indicates the distance between the pins. For example, a GU24 base’s pins are 24mm apart.

That’s all fine and dandy but what is the point? Why would anyone want or need to use a GU base bulb or fixture?

There are several advantages to using these bulbs over your traditional screw base bulbs, and much of it has to do with the technology inherent to the GU bulb, itself. For starters, GU bulbs are self-ballasted. Ballasts regulate the flow of energy through the bulb and provide sufficient voltage to create light. Without a ballast, there is nothing preventing the bulb from drawing too much power and stop the current from reaching destructive levels that would ultimately cause a rapid (and possibly violent) death of the lamp. In more simpler terms, a ballast provides stability and control to a light bulb. GU bulbs have a built-in ballast, enabling them to be used in fixtures that are not equipped with such technology. This makes them super easy to replace when they do reach their end of life.

Next, GU base bulbs use much less energy and have a significantly longer lifespan than their screw-in counterparts, which makes them ideal for use in almost any capacity. There are very few GU bulbs that do not meet Energy Star standards, and most are Title 24 compliant as well. In fact, as a direct result of these factors, some states actually require newly constructed buildings to be furnished with GU24 socket fixtures to guarantee that energy-hungry incandescent bulbs cannot be used.

Finally, GU bulbs are comparable in size to your more traditional bulbs and were ultimately designed to give a visual cue in differentiating between standard and energy-efficient lamps. Their smaller size is important for projects with fixtures that do not allow for much wiggle room as these bulbs are generally shorter in length than, say, a typical CFL bulb with a medium screw E26 base. However, they are more notably found on LEDs of all shapes and sizes, which can be viewed as a kind of double whammy with regard to communicating the whole energy conservation theme. You know, since LEDs have become the golden standard in energy-efficient lighting and all, combining them with GU bases basically screams, “USE ME TO SAVE MONEY!”

Some examples of bulb shapes that use GU bases include A19, R30, BR40, PAR38, PL, MR16, Downlight Modules, and CFL Spiral or Twist bulbs, and GoodBulb is your go-to source for them all! Call, email, or chat with one of our lighting specialists today to find the perfect GU light bulb for any project, big or small.