When should you not use LED bulbs?

No single blanket scenario rules out LED bulbs entirely, but LED bulbs are the wrong choice when the fixture is rated for enclosed housings only and the specific LED lacks that rating, when dimmer switches are incompatible with LED driver circuits, or when an application requires instant full-spectrum infrared output that LEDs don't produce.

The most common real-world mismatches involve enclosed fixtures and dimmer compatibility. Standard LED bulbs trapped in fully sealed recessed cans without an "enclosed fixture rated" label run hotter than designed, which shortens lifespan significantly — sometimes from 50,000 hours down to under 10,000. Similarly, LED bulbs paired with older incandescent-only dimmer switches produce flicker, hum, and reduced dimming range because the dimmer's minimum load threshold exceeds what LED driver circuits draw.

• LED bulbs in non-rated enclosed fixtures can drop rated lifespan from 50,000 hours to under 10,000 hours due to heat buildup.
• Most LED bulbs require a dimmer rated for LED/CFL loads; incandescent-only dimmers typically require 250–600W minimum load that LEDs don't meet.
• LED bulbs are not suitable replacements for UV-output or infrared heat lamp applications — LEDs emit negligible UV and infrared radiation.
• Extreme cold environments below -4°F (-20°C) can prevent some LED drivers from starting reliably without a cold-rated fixture spec.