How to Identify Fluorescent Lights

Fluorsecent lamps have identification codes on the bulb.
Fluorsecent lamps have identification codes on the bulb. (Image: Jupiterimages/ Images)

The color of the light is the most obvious way to identify fluorescent lighting. But there is more to fluorescent lighting than just whether the bulb gives out warm or cool light. For example, fluorescent light bulbs can be rapid-start or preheated. Variations are identified by a standardized code marked on the light bulb. Different types of fluorescent light bulbs include high output bulbs and variously shaped bulbs. Compact fluorescent bulbs are classified differently by manufacturers than tube fluorescent bulbs.

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Hold the lamp by its glass tube and find its identification number near the ends of the lamp, where the electrical connection is located. An example of a standardized identification number is "F30T12/CW/RS."

Break up the code. The first letter, "F" indicates that the lamp is fluorescent. Another possible code in this position is "FC" which would mean that the bulb is a fluorescent circular bulb. "FB" or "FU" indicate that the bulb is "bent" or "U-shaped," depending on the bulb manufacturer.

Identify the number that follows the light bulb shape indicator, such as in the example. The "30" in the example indicates that the lamp is rated at 30 watts. The specific wattage of the bulb is listed here.

Identify the the following character in the code, which is a letter. In general, it will be a letter "T" which tells you the light is tube shaped. There are no other designations used here, as the tube shape is the industry standard for fluorescent lighting.

Decipher the last number in the series. In the example, the number "12," indicates the diameter of the tube in eighths of an inch. In the example, this means that the tube is 12/8 inch in diameter, or 1-1/2 inches.

Decipher the final two indicators of the light code. "CW" means "cool white," indicating the temperature range of the color emitted by the light. "WW" stands for "warm white" while "RS" means "Rapid Start." Other designations include "CWX," which means "cool white deluxe," indicating an instant start lamp, "VHO" or "HO," which mean, respectively, "Very High Output" and "High Output." This designation relates to the amount of current applied to the bulb. VHO bulbs function above 1500mA, while HO bulbs function above 800mA.

Tips & Warnings

  • Fluorescent bulbs are available in other shapes besides straight tubes, including circular round bulbs and U-curved fluorescent bulbs. Compact fluorescent bulbs have their own system of identification that is different from standard fluorescent bulbs.
  • Fluorescent lighting that is used outdoors must be contained within a waterproof housing. CFL bulbs are acceptable for use in outdoor lighting to replace entryway lights.


  • "The Home Lighting Effects Bible: Ideas and Know-How for Better Lighting in Every Part of Your Home"; Lucy Martin; 2010
  • "Lighting Design Basics"; Mark Karlan; 2004
  • "The Complete Home Lighting Book: Contemporary Interior and Exterior Lighting for the Home"; James Davidson; 1997
  • Lightsearch: Fluorescent Lamp Identification
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