T12 Vs. T8 Fluorescent Lights

Some systems require more energy than others and therefore are more expensive. For instance, incandescent bulbs--those rounded glass filamented devices invented by Thomas Edison---use more electricity than newer fluorescent lamps. In the common lighting fixtures, however, there is a choice between the T8 and the T12 fluorescent lamps, which are more preferred than T5 bulbs because they use less electricity.

  1. Composition

    • Fluorescent lamps are lighting systems composed of mercury vapor and phosphor coating inside a glass tube, which is either a long, straight tube, U-shaped, circle or spiral in form. The last is called a compact fluorescent lamp because it can be about the size of an incandescent bulb. Electrical energy is passed through the vapor and phosphor to make the phosphor glow and produce light. The electricity flow is regulated by a device called ballast to keep the phosphor glowing and produce light continuously. Fluorescent tube diameter sizes are given in eighths of an inch; a T12 is 1.5 inches and T8 is 1 inch. The wattage indicated is normally 5/6 of the tube length; thus, a 40-watt lamp is 48 inches, and a 30-watt is 36 inches long.

    Energy Use

    • Being smaller in diameter, less amounts of phosphor and mercury vapor are used in T8 lamps compared with T12. The T8 thus requires less energy for about the same amount of produced light. For example, an F34T12 lamp will use 44 watts, while a comparative F32T8 lamp will require only 25 watts, a reduction of 19 watts, or 43.18 percent. A four-piece assembly will use 52 watts, or 35.13 percent less energy.

    Brightness Factor

    • For the last example in Section 2, there is actually a 3 percent to 12 percent increase in illumination according to the type of lamp used. The T8 lamp likewise normally produces higher Color Rendering Index (CRI), the capability of the light source to reproduce the original color of the object being lighted.

    Flickering

    • T8 lamps using electronic ballasts run at 20 kilohertz, which is usually too fast for the human eye to visibly detect. Thus it produces less strain on the eyes, which must adapt constantly to lighting conditions. Ordinary fluorescent lamps may have a 120 or 100 hertz flicker, which can become annoying to some fish or reptile keepers.

    Other Considerations

    • In T8 lamps, unlike T12 bulbs, the "hum" created by the ballast manufacturing design flaws is virtually eliminated through the use of electronic ballasts. A T8 lamp may also last longer, having a lifespan of 18,000 to 30,000 hours if the ballast used is correct. Less cooling needed when using T8 lamps. Because T8 lamps use less energy, the resulting heat is also lower, translating to less power needed from the cooling systems used in the room. Also because of less electricity use, T8 bulbs are more environmentally friendly.