How much light do you get for the power used? This is an important concept when selecting types of lamps (lightbulbs.) A high efficacy lamp produces a lot of light per watt of power consumed.

Incandescent vs Fluorescent

To use a standard that most people are familiar with, a standard 60 watt incandescent lamp is rated at 890 lumens (14.8 Lumens/Watt.) A 13 Watt CFL that is also rated at about 890 lumens. (68 Lumens/Watt) This means that the CFL has more than 4 times the luminous efficacy.

This standard of measurement makes sense for non-directional lamps, but for Halogen spotlights and flood and LED lamps, it makes more sense to measure the amount of light that reaches the surface that you are trying to light.

Halogens & LEDs - Directional Lighting

Halogen and LED lamps are most often used in directional light sources. Halogen lamps, such as MR16s, & PAR bulbs, and LEDs have reflectors to direct the light. Most lamp manufacturers do not publish lumen output ratings for reflectorized lamps in their catalogs. Instead, they publish beam angle and CBCP, which provide more accurate information about the performance characteristics of the lamp. Tests of several 50-watt MR16 samples of the same type (EXN) showed a lumen output ranging from 560 lumens to 710 lumens, (average: 625 lumens.) (12.5 Lumens/Watt). A 50 Watt PAR20 halogen bulb puts out about 550 Lumens (11 Lumens/Watt). A LED bulb sold to fit in fixtures designed for halogen PAR20 bulbs, EcoLEDs 3 x 1-watt LED light, puts out 135 lumens/3 watts (45 lumens/watt.)

The EcoLEDs 3 x 1-watt LED light is billed as equivalent to a 40 Watt incandescent bulb. At first glance this seems misleading since a 40 Watt incandescent puts out close to 600 Lumens. But when the light reaching a desk surface 2' away is measured, all of the 135 FC from the LED are there, but from the 40 Watt incandescent, only 10 FC of light reach the desk. The problem is that 135 Lumens is way less than the 625 put out by the 50 Watt halogen. For its size, the LED light output is very wimpy.

I just bought one of these LED bulbs to see it in action, realizing that there is another problem for most consumers: the 3 Watt LED costs over $40 with shipping!

Although reflector lamps may have lower luminous efficacies than non-directional sources, they tend to be more effective at putting the light where it is needed without wasting much light elsewhere. This can result in energy savings. LRC's article on MR16s includes some good examples of this comparison.

When selecting a type of lightbulb or fixture, it is also important to consider how long the bulb will last.

LRC has conducted many tests on performance and longevity of different lamps.