Energy-efficient Fluorescent Tubes

What is Energy-efficient Fluorescent Tubes?

A fluorescent tube (or fluorescent lamp) is operated with gas-discharge principle that uses electricity to excite mercury vapor. Electricity excites mercury atoms which then produces short-wave ultraviolet light. The ultraviolet light then causes a phosphor coating to fluoresce to produce visible light. Compare to the incandescent lamps, fluorescent tubes convert electrical power into useful light more efficiently, so we call them Energy-efficient fluorescent tubes.

Fluorescent tube lamp

phosphor coating, mercury and inert gases and base with bi-pin plug

Advantages of Energy-efficient fluorescent tubes

Luminous efficacy

The efficiency of fluorescent tubes is much higher than that of incandescent lamps, which means more input power can be converted to visible light by using fluorescent tubes than incandescent lamps. Fluorescent lamps use 25%-35% of the energy used by incandescent lamps to provide the same amount of illumination.


Typically a fluorescent tube lasts about 10 times (15,000 - 30,000 hours) that of an equivalent incandescent lamp. The longer life may also reduce lamp replacement costs, providing additional saving especially where labour is costly.

Lower luminosity

Compared with an incandescent lamp, a fluorescent tube is a more diffuse and physically larger light source. In suitably designed lamps, light can be more evenly distributed without point source glare as seen in an undiffused incandescent filament.

Average efficacy (Lumens/Watt) of various light sources:

Lighting Comparison Chart
Lighting Type Efficacy (lumens/watt) Lifetime (hours) Color Rendition Index (CRI) Color Temperature (K)
Standard "A" bulb 8-17 1,000-1,500 98-100 (excellent) 2,700-2,800 (warm)
Tungsten halogen 11-21 2,000-3,000 98-100 (excellent) 2,900-3,200 (warm to neutral)
T5 / T8 80-110 15,000-30,000 60-95 (good) 2,700-6,500 (warm to cold)
Compact fluorescent lamp (CFL) 50-70 6,000-15,000 70-85 (good) 2,700-6,500 (warm to cold)
Light-Emitting Diodes
LED lamp 60-130 15,000-30,000 70-95 (good) 2,700-6,500 (warm to cold)

Fluorescent Lamp Labelling

F = Fluorescent
T = Tubular lamp shape
8 = lamp diameter in 1/8 inch increment

T5 = 5/8 inch = 16 mm
T8 = 8/8 inch = 1.0 inch = 26 mm
T10 = 10/8 inch = 1.25 inch
T12 = 12/8 inch = 1.5 inch = 38 mm

T5, T8, T12 Fluorescent Lamp

Fluorescent lamps, T12, & T8, have long been used as energy-efficient lamps for general lighting. New generation of T5 fluorescent lamps with 16mm dia. has recently been developed for improved efficient (110 lm/W) and performance.

Characteristics of T5 Fluorescent Lamps:

The standard wattage of the T5 lamps range from 14W, 21W, 28W to 35W. High output versions are also available for some special applications. Operated with high frequency electronic ballasts, these new lamp types fulfill the principle of cost-effectiveness. T5 lamps have the highest luminous efficacy of about 110 lm/W, when compared with T12 and T8 lamps (70 lm/W and 80 lm/W respectively). The maximum light output occurs when its ambient temperature is 35°C. At room temperature of 25°C, the T5 lamps installed in a typical recessed modular luminaire with parabolic reflectors will be operating very close to their optimum temperature.