Learning Center :: Lighting Efficiency Ratings

Lighting Efficiency Ratings

A standard way of rating lighting efficiency is in lumens per watt--this figure accounts for all of the light produced by a bulb. This rating does not necessarily reflect how much usable light is is thrown on your work area. The reflector and fixture will have a large effect on this. So be sure to read our guidelines for each type of lighting discussed below--lights that show a lower efficiency may still save you energy depending on the application.

Be aware of the different ways that lighting efficiency can be represented. For example, there's a big difference between two common LED manufacturer's efficiency specs -- some show only lumens per watt of light output, while others show lumens per watt used by the LED. The latter is useful information, a true efficiency rating. The former does not include power wasted as heat, and is useless for evaluating lighting in an off-grid home.

But wait! What about all the white LED high-efficiency claims that are all over...including the claims that used to be on this site?

Unfortunately, much of this information is incorrect. Comparing the efficiency of a white LED light with a compact fluorescent by measuring the intensity of a tiny spot within the beam does NOT give proper efficiency results. We got much of our data for efficiency claims from an article in Home Power Magazine (click here to see this testing article) and in literature from LED distributors. The problem? All of the light from our LEDs is concentrated in a 20 degree beam, while the incandescent and compact fluorescent lights were tested without fixtures...and most of the light they produced was never measured in the test, since it sensed only light falling on the sensor. It's OK to compare different lights by how brightly they illuminate a certain size area...but put a reflector behind the compact fluorescent and incandescent bulbs in the test rig and the data would change significantly. Therefore, while the LED lights in this test may illuminate a small area as brightly as other lights, they are NOT significantly more efficient.

LEDs can still be a good choice for illuminating your workbench, for example, as long as the light cast onto your small work area is as bright as you need--in this case your LED light could be a good investment for saving power, especially if your old incandescent fixture is also lighting the rest of the room where you don't need the light (like in the Home Power experiment link above).

If you try and light an entire living room with an LED fixture, though, you are not saving much--in that case you want a wide dispersal of light, and a fluorescent fixture would be the hands-down winner for efficiency, cost and practicality.

Another thing to keep in mind--notice that with current commercial lighting products, the smaller the incandescent bulb, the less efficient it is. For small-sized and lower-light-intensity applications such as task and reading lights, pathway lighting, exit signs, and flashlights, LED lights will be much more efficient than the equivilant small incandescent.

This is because fluorescent light products in these small sizes are not available commercially. We are currently researching remote power applications for small cold-cathode fluorescents, which are commonly used to backlight LCD screens. We hope to have more information about these lights soon, though they are still significantly larger than LED products...too big to use in anything smaller than a very large flashlight.

Energy Performance Specialists • 4915 Farwell St., #3 McFarland, WI 53558