CFL bulbs
Compact fluorescent lamps produce light by exciting mercury vapor with an electric arc. The UV light generated is converted to visible light by the phosphor coating inside the tube. They were the dominant energy-saving alternative to incandescent bulbs before LED prices fell.
Key specifications
| Property | Typical value |
|---|---|
| Efficacy | 40–70 lm/W |
| Lifespan | 6,000–15,000 hours rated |
| CRI | ~82 standard; 90+ in specialty CFLs |
| Warm-up time | 30 seconds to 3 minutes to full brightness |
| Color temperature | 2700 K, 3000 K, 3500 K, 4100 K, 5000 K |
| Mercury content | 3–5 mg per bulb |
| Cold-temperature performance | Poor — slow start and reduced output below 5 °C |
| Dimmable | Specific dimmable models only |
Mercury — disposal rules
CFLs contain mercury and must not go in regular household trash. Dispose at a retailer hazmat drop-off (many hardware stores accept them), a municipal hazardous waste collection, or an EPA-certified recycler.
If a CFL breaks indoors: ventilate the room 5–15 minutes before cleaning. Do not vacuum — collect fragments with damp paper towel, seal in a plastic bag, and dispose at a hazmat drop-off.
Dimmability
Standard CFLs are not dimmable. Dimmable CFL models exist but require a dimmer designed for CFL loads — not a standard incandescent dimmer. Even dimmable CFLs have a limited range (typically 20–30% minimum) and may buzz at low levels.
Frequent switching reduces lifespan
CFL lifespan is rated at 3-hour cycles. Switching off and on frequently (e.g. a bathroom used for 2-minute visits) significantly shortens rated life. LED is better for frequently switched fixtures.
When CFL is still reasonable
- You have existing stockpiled CFLs and want to use them before replacing
- Fixtures that stay on for extended periods (reducing switch-cycle stress)
For all new purchases, LED is the better choice: no mercury, instant brightness, longer lifespan, lower operating cost.