Recessed downlights are the dominant ceiling fixture in modern US homes — and one of the most commonly misunderstood. Using the wrong bulb type, wrong size, or wrong retrofit kit leads to wasted light, poor aesthetics, and shorter bulb life. This guide covers everything from basic can size identification to retrofit kit installation and the energy math on transitioning from halogen to LED.
Can Size: Start Here
Every recessed fixture has a nominal diameter that determines which bulbs and trim kits fit. In the US, most residential recessed cans are one of three sizes:
- 4" (102mm): Most common in hallways, closets, and as accent lights. Use PAR20, BR20, or a 4" retrofit kit.
- 5" (127mm): Common in housing built from 1980–2005. Use PAR30 or a 5" retrofit kit. Note: 5" and 6" don't interchange.
- 6" (152mm): The current standard for kitchens, living rooms, and general residential construction. Use BR30, PAR30, or a 6" retrofit kit.
If you're not sure what size your cans are: measure the opening diameter of the trim ring. The number in inches (approximately, it won't be exact) is your can size.
Retrofit Kits vs. Replacement Bulbs
You have two approaches to LEDing your recessed fixtures:
- Replacement bulbs (BR30, PAR30): Simply screw into the existing housing. Fast, cheap, reversible. Moderate efficiency — the fixture was designed for a different bulb form factor. OK for most residential use.
- Retrofit kits (integrated LED modules): Replace the entire trim assembly with a purpose-built LED module. Higher upfront cost, better optical efficiency, sleeker appearance, longer lifespan. Often dims more smoothly and to a lower percentage. For kitchens and main living areas, retrofit kits are worth the premium.
IC Rating and Air-Tightness
Before buying any downlight or retrofit, check two critical ratings:
- IC-Rated: If your ceiling has insulation above it (most homes do), you must use an IC-rated fixture. Non-IC rated fixtures can overheat when surrounded by insulation, creating a fire risk. Check the existing housing for an IC-AT label — if you're installing a retrofit kit, the kit itself must be IC-rated.
- Air-Tight (AT): Recessed fixtures without airtight gaskets allow conditioned air to leak into the attic, significantly increasing heating and cooling costs. Airtight-rated retrofit kits seal this gap. In cold climates, this can save $50–100+/year per 10 fixtures in energy costs alone.
Key Specs at a Glance
| Spec | Downlight Recommendation | Why It Matters |
|---|---|---|
| Can size | Measure your trim ring opening first | 4", 5", 6" don't interchange |
| Bulb shape | BR30 (6" can), BR20/PAR20 (4" can) | Directional — no light wasted upward |
| IC Rating | Required if ceiling has insulation above | Fire code requirement |
| Color Temp | 2,700K–3,000K (living/bedroom), 4,000K (kitchen/office) | Match to room function |
| Lumens | 650–1,100 lm per fixture | Adequate for most residential applications |
| Beam angle | 40°–80° flood for general use | Too narrow = spotlights; too wide = inefficient |
| Dimmable | Yes — always | Fixed-brightness recessed cans are limiting |
Our Top Picks for 2026
Sunco 6" Retrofit Recessed Downlights (12-Pack)
Bulk-pack value for complete ceiling retrofits. Fast plug-and-play installation with standard E26 adapters.
Watts: 13W | Dimmable: Yes | Certification: UL Listed / Energy Star |
Warranty: 7 Years
Honest Limitation: Cannot change color temperature after installing (fixed 3000K)
Check Price on AmazonTORCHSTAR 6" Selectable CCT Recessed Retrofit Downlight
CRI 90+ selectable CCT (2700K-5000K). Features a deep baffle trim design that reduces overhead glare.
Watts: 12W | Dimmable: Yes | Certification: Energy Star / Title 24 |
Warranty: 5 Years
Honest Limitation: Slider switch is on the back of the module; must set CCT before ceiling install
Check Price on AmazonHalo RL560 series 6" Selectable Recessed Downlight
The professional electrician standard. Features outstanding construction, wet-rating for showers, and flawless dimming down to 5%.
Watts: 10.5W | Dimmable: Yes | Certification: UL Listed / Energy Star |
Warranty: 5 Years
Honest Limitation: Higher price point than typical Amazon-native multipacks
Check Price on Amazon