Norman Lamps, Inc.

T12 fluorescent tubes are the oldest and largest diameter linear fluorescent bulbs still in common use, with a 12/8-inch (1.5-inch) diameter that was the commercial lighting standard for decades before being largely superseded by more efficient T8 technology. While T12 tubes have been phased out in many regions due to energy efficiency regulations and are no longer manufactured in standard configurations in the United States, millions of T12 fixtures remain in service, and replacement tubes continue to be necessary for maintaining these existing systems.

The most common T12 size is 4 feet (48 inches) consuming 40 watts, though 8-foot versions (75 watts or 95 watts) are found in industrial facilities, and 2-foot and 3-foot tubes serve various applications. T12 tubes use medium bi-pin (G13) bases – the same base as T8 tubes, which has led many facility managers to explore T8 retrofits since the sockets are compatible. However, successful conversion requires replacing the ballast as well, since T12 magnetic ballasts won't properly operate T8 tubes.

The efficiency difference between T12 and T8 technology is substantial. A 40-watt T12 produces roughly the same light output as a 32-watt T8, meaning the T8 achieves 20% better efficacy. When you factor in the improved efficiency of electronic ballasts (nearly always used with T8) versus the magnetic ballasts common in T12 fixtures, the system-level efficiency difference approaches 30-40%. This is why government regulations in many countries have phased out standard T12 production – the energy waste was simply too significant.

Ballast compatibility issues complicate T12 tube replacement. Older T12 fixtures used magnetic ballasts that are less efficient, can hum audibly, and cause the characteristic flicker sometimes associated with fluorescent lighting. These magnetic ballasts are becoming increasingly difficult to source as manufacturers have ceased production. When a magnetic ballast fails in a T12 fixture, replacing the entire fixture or retrofitting to T8 or LED typically makes more economic sense than sourcing another magnetic ballast.

Color temperature options in T12 tubes mirror other fluorescent technologies where available: warm white (3000K), cool white (4100K), and daylight (5000K+). However, availability has become limited as production has wound down. Many facilities maintaining T12 systems face decreasing product selection and potentially higher prices for the remaining inventory of replacement tubes.

For facilities with functioning T12 lighting systems, the decision point usually comes when tubes or ballasts need replacement. Continuing with T12 replacements is the lowest upfront cost but commits to higher ongoing energy expenses. Retrofitting to T8 requires new ballasts but uses existing fixtures and sockets, offering good efficiency gains at moderate cost. LED retrofits require more upfront investment but deliver the best long-term economics through superior efficiency and virtually eliminated maintenance.

Some facilities in specialized applications may need to maintain T12 systems for legitimate reasons – perhaps matching existing light levels in portions of a building, maintaining consistent appearance, or working with very old fixtures where retrofit options are limited. For these situations, stockpiling T12 tubes while they're still available can ensure long-term supply, though storage conditions matter for fluorescent tubes (cool, dry locations preserve maximum life).

Standard Sizes: 2-foot (24"), 3-foot (36"), 4-foot (48" - most common), 8-foot (96"). Medium bi-pin (G13) bases.

Common Wattages: 20W (2-foot), 30W (3-foot), 34W or 40W (4-foot), 75W or 95W (8-foot)

Status: Phased out in many regions due to efficiency regulations. Replacement tubes still available but selection decreasing. Consider retrofitting to T8 or LED when replacements needed.