| Comparison to Traditional Light Sources
Although originally intended for directional lighting, recessed downlights are now used widely for general ambient lighting in kitchens, hallways, bathrooms, and other areas of the home. Other types of downlights using spot lamps, reflectors, and lenses are also used for art, accent, display, and wall lighting. In some applications, like media rooms and dining areas, downlights are operated on dimming circuits. The most common light source used in residential downlights is a 65-watt incandescent reflector-style lamp with a standard Edison base. Other commonly used options include A-type incandescent lamps, and PL-type, spiral, or reflector CFLs.
The light output of a traditional recessed downlight is a function of the lumens produced by the lamp and the luminaire (fixture) efficiency. Reflector-style lamps are specially shaped and coated to emit light in a defined cone, while “A” style incandescent lamps and CFLs emit light in all directions, leading to significant light loss unless the luminaire is designed with internal reflectors. Downlights using non-reflector lamps are typically only 50% to 60% efficient, meaning about half the light produced by the lamp is wasted inside the fixture. Recently, LED downlights have come on the market. Table 1 provides examples of performance data for residential recessed downlight using several different light sources, including two LED products. These data should not be used to generalize the performance of fixture types, but are provided as examples.
Table 1: Examples of Recessed Downlight
Performance Using Different Light Sources |
| |
Incandescent* |
Fluorescent* |
LED** |
65W BR-30 Flood |
13W 4-pin Spiral CFL |
15W R-30 CFL |
LED 1 |
LED 2 |
| Rated lamp lumens |
725 |
860 |
750 |
|
|
Lamp wattage
(nominal W) |
65 |
13 |
15 |
|
|
Delivered light output
(lumens), initial |
652 |
514 |
675 |
300 |
730 |
Luminaire wattage
(nominal W) |
65 |
12 |
15 |
15 |
12 |
Luminaire efficacy
(lm/W) |
10 |
42 |
45 |
20 |
60 |
*Based on photometric and lamp lumen rating data for commonly available products. Actual downlight perfor-mance depends on reflectors, trims, lamp positioning, and other factors. Assumptions available from PNNL.
|
|
| **Results for two commercially-available products tested. LED 1 was tested in Aug 2006. LED 2 was tested in Sep 2007. Lamp level data are not available for the LED downlights, which contain proprietary LED arrays, heat sinks, reflectors, and diffusers. |
The 13W spiral and 15W reflector CFL systems have similar luminaire efficacy and
both lamp types are readily available from all of the major lamp manufacturers.
Available LED products vary widely in light output and efficacy. LED 1 provides less
than half the delivered light output of the 15W reflector CFL, but the newer LED 2 fixture provides more net lumens than the 15W RCFL or the 65W incandescent and has the highest overall luminaire efficacy of the options shown here.
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