The differences of t5, t8 and t12 Fluorescent Lamp Types

T5 tubes are the latest series of fluorescent lamps. They are offered in standard or high-output (HO) options. There are many differences between T5 lamps and T8 or T12 lamps.

T5 vs. T8/T12


T5 tubes are smaller than T8 and T12 tubes, which allow them to fit into smaller spaces. They are offered in sizes of 2-5 feet in length. T5 lamps are around 40% smaller than T8 lamps and almost 60% smaller than T12 lamps. T5 lamps have a G5 base (bi-pin with 5 mm spacing), while T8 and T12 lamps use a G13 base (bi-pin with 13 mm spacing). Because of a .625-inch bulb diameter, and a mini bi-pin base, the T5 lamp can be used in lower profile areas.

Output and Performance

The T5 lamp has a generally lighter output compared to the T8 lamp. The T5 is offered in color temperatures of 3000K, 3500K and 4100K. They have a color-rendering index (CRI) of 82 or 85, compared to the T8 with a CRI of 75 or 85. The T5 system provides its peak output at 35°C as opposed to the T8 or T12’s peak output at 25°C. This makes the T5 system a better choice in an output over temperature ratio, and a better choice to use for effective lighting in small, and low circulated spaces. With power ratings of 24, 39, 54, and 80, the T5 HO lamp easily beats the T8 or T12 system with over double the output. T5 lamps are generally rated for 20,000 hours, as compared to T8 lamps, which are generally rated for 24,000 hours.

T8 or T12 fixtures must be suspended over 2 feet from the ceiling in order to have effective light. This would be too low for many office buildings where ceilings are rarely high. With T5 lamps, suspension from the ceiling can be as little as 15 inches.

Mercury Content

The T5 lamp has a lower mercury content than T8 and T12 lamps, yet it performs with the same or greater efficiency. The lamp has a coating on the inside of its glass wall that stops the glass and phosphors from absorbing mercury. This barrier coating reduces the amount of mercury needed from approximately 15 mg to 3 mg per lamp. Since mercury absorption causes the lamp’s light output to depreciate over its life, the coating helps to keep light levels much closer to initial output (only a 5% depreciation in the first 40% of its life). The lower mercury absorption also keeps the light’s output as strong as its initial output, throughout its life.

T5 vs. T5 HO

The T5 and T5 HO are the same size, but have different outputs. The T5 has an output of 2,900 lumens, similar to the T8 output. The T5 HO has up to 5,000 lumens. With the T5 HO lamps, fewer lamps can be used on projects, which save money due to less maintenance. The high output and thinness of the lamps lets them be available for indirect and shallower lighting. Every T5 HO lamp requires its own ballast, but they are 10-15% less efficacious than normal T5 models. T5 HO ballasts also have many features such as a dimming function, or operating multiple F54 lamps.


T5’s are the first linear lamps to use electronic ballasts only. One T5 ballast can power one or two T5 lamps of any wattage, because they all run at the same current. Their different wattages have the same brightness, which stays the same with any length of the product.

Because of the lamp’s small size and high power, temperature can rise as the lamp dies because of less cathode emission material. This rise in temperature can cause the bulb wall to crack. The T5 ballasts have an “end-of-life circuitry”, which stops the bulb from cracking by shutting off the lamp when there is a rise in voltage.

T5 and T5 HO lamps are increasingly used in offices and industrial areas. The T5 HO system can be used in any area with a ceiling higher than 15 feet, including gymnasiums and warehouses. The T5 offers over 50% more energy saving then a 400 watt metal halide system.

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