Luminous Efficacy - Lighting Efficiency - Examples


The following table lists luminous efficacy of a source and efficiency for various light sources:

luminous efficacy (lm/W)
luminous efficiency
Combustion candle 0.3 0.04%
gas mantle 1–2 0.15–0.3%
Incandescent 100–200 W tungsten incandescent (230 V) 13.8–15.2 2.0–2.2%
100–200–500 W tungsten glass halogen (230 V) 16.7–17.6–19.8 2.4–2.6–2.9%
5–40–100 W tungsten incandescent (120 V) 5–12.6–17.5 0.7–1.8–2.6%
2.6 W tungsten glass halogen (5.2 V) 19.2 2.8%
tungsten quartz halogen (12–24 V) 24 3.5%
photographic and projection lamps 35 5.1%
Light-emitting diode white LED (raw, without power supply) 4.5–150 0.66–22.0%
4.1 W LED screw base lamp (120 V) 58.5–82.9 8.6–12.1%
5.4 W LED screw base lamp (100 V 50/60 Hz) 101.9 14.9%
6.9 W LED screw base lamp (120 V) 55.1–81.9 8.1–12.0%
7 W LED PAR20 (120 V) 28.6 4.2%
7 W LED PAR20 (110-230 V) 60.0 8.8%
8.7 W LED screw base lamp (120 V) 69.0–93.1 10.1–13.6%
Theoretical limit (white LED) 260.0–300.0 38.1–43.9%
Arc lamp xenon arc lamp 30–50 4.4–7.3%
mercury-xenon arc lamp 50–55 7.3–8.0%
Fluorescent T12 tube with magnetic ballast 60 9%
9–32 W compact fluorescent 46–75 8–11.45%
T8 tube with electronic ballast 80–100 12–15%
PL-S 11 W U-tube, excluding ballast loss 82 12%
T5 tube 70–104.2 10–15.63%
Gas discharge 1400 W sulfur lamp 100 15%
metal halide lamp 65–115 9.5–17%
high pressure sodium lamp 85–150 12–22%
low pressure sodium lamp 100–200 15–29%
Cathodoluminescence electron stimulated luminescence 30 5%
Ideal sources Truncated 5800 K blackbody 251 37%
Green light at 555 nm (maximum possible luminous efficacy) 683.002 100%

Sources that depend on thermal emission from a solid filament, such as incandescent light bulbs, tend to have low overall efficacy compared to an ideal blackbody source because, as explained by Donald L. Klipstein, “An ideal thermal radiator produces visible light most efficiently at temperatures around 6300 °C (6600 K or 11,500 °F). Even at this high temperature, a lot of the radiation is either infrared or ultraviolet, and the theoretical luminous is 95 lumens per watt. No substance is solid and usable as a light bulb filament at temperatures anywhere close to this. The surface of the sun is not quite that hot.” At temperatures where the tungsten filament of an ordinary light bulb remains solid (below 3683 kelvins), most of its emission is in the infrared.

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