Norman Lamps, Inc.

BT15 halogen bulbs feature a distinctive bulged tubular shape that's 15/8 inches (1.875 inches) in diameter, providing efficient halogen technology in a compact form factor that works well in decorative fixtures, ceiling fans, enclosed fixtures, and various residential and light commercial applications. The BT designation indicates "bulged tubular" – the bulb has a rounded, slightly bulged tubular shape rather than the standard A-shape pear form or strictly cylindrical tube. This shape allows for compact fixtures while providing adequate envelope surface area for heat dissipation.

These bulbs serve as energy-efficient alternatives to traditional incandescent bulbs while meeting efficiency standards through halogen technology. A 43W BT15 halogen provides light output equivalent to a 60W traditional incandescent, a 53W BT15 equals a 75W incandescent, and a 72W BT15 replaces a 100W incandescent. The energy savings of roughly 25-30% isn't as dramatic as LED or CFL, but BT15 halogens offer perfect color rendering (CRI 100), instant full brightness, smooth dimming with any dimmer, and light quality identical to traditional incandescent bulbs many people prefer.

The compact BT15 shape makes these bulbs particularly suitable for enclosed fixtures, ceiling fans, and smaller decorative fixtures where larger A19 bulbs might not fit or would look disproportionate. Many ceiling fan light kits specify BT15 bulbs because the smaller diameter allows multiple bulbs to fit in the limited space of the fan housing. Enclosed fixtures benefit from the smaller envelope because the reduced surface area (compared to larger bulbs) means less volume to heat up in the enclosed space.

Base types on BT15 halogen bulbs are typically medium (E26), the standard screw base that fits household sockets. This makes BT15 halogens drop-in replacements for traditional incandescent bulbs in fixtures where the smaller bulb size is appropriate or preferred. Some ceiling fan manufacturers specifically recommend or require BT15 bulbs for their fan light kits, making these bulbs essential for properly equipped fans.

Color temperature in BT15 halogen bulbs runs around 2900K, slightly warmer than standard incandescent's 2700K but close enough that the difference isn't noticeable in most applications. The light has that warm, inviting quality people associate with traditional incandescent lighting, without the stark brightness of daylight bulbs or the slight greenish cast that some CFLs exhibit. For people who value the light quality of incandescent but want to meet efficiency standards, BT15 halogen provides a practical compromise.

Lifespan for BT15 halogen bulbs typically runs 1,000-3,000 hours, considerably longer than old-style incandescent bulbs but far less than LED (which typically lasts 15,000-25,000 hours). The trade-off is acceptable for many users: BT15 halogen bulbs cost less upfront than LED, work perfectly with all dimmers, provide familiar light quality, and last long enough that replacement frequency isn't burdensome in residential applications. For ceiling fans and fixtures that don't operate many hours daily, 2,000-hour life might translate to 2-3 years of service.

LED alternatives to BT15 halogen bulbs have become available, offering 75-85% energy savings and much longer life. However, some ceiling fan manufacturers specifically require halogen or incandescent bulbs and warn against using LED or CFL due to potential interference with fan controls or incompatibility with enclosed fan housings. Before switching to LED in ceiling fans or enclosed fixtures, verify that the manufacturer permits LED use and that the LED bulbs you're considering are rated for enclosed fixtures.

Common Wattages: 43W (60W equivalent), 53W (75W equivalent), 72W (100W equivalent)

Base Type: Medium (E26) - standard household screw base

Typical Life: 1,000-3,000 hours depending on specific bulb and operating conditions

Applications: Ceiling fan light kits, enclosed fixtures, decorative fixtures, table lamps, floor lamps, anywhere compact efficient halogen is preferred