T5 Vs. T3 Halogen Bulb

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Spotlights use halogen bulbs.

Because of the halogen gas added inside halogen light bulbs, the tungsten filament burns hotter, brighter and longer with the same amount of electricity, making halogen bulbs the best choice for high-intensity lighting.



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Halogen bulbs come in a wide variety of sizes and shapes, from peanut size to 10-inch tubes. They have a variety of connection types, including plug in, screw in, double ended and twist in.


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Decorator and novelty lamps use smaller halogen bulbs. Track lighting, high intensity lamps, studio lights and spotlights all use larger-sized halogen lamps.


The filament of any halogen light bulb is made of tungsten. Different grades of tungsten alloys burn at slightly different intensities.


T Designation

Any halogen light bulb may or may not have a T designation, which only tells the grade of tungsten used in the filament. The T does not indicate size, shape or power.

T3 and T5 Difference

Different halogen bulbs use different grades of tungsten filaments. T5, made with a tungsten cobalt alloy, lasts slightly longer than a T3, made without cobalt.