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Paradigm shifting: Power and light

Used to be we’d buy lightbulbs by the watt. Collin Cole notes that times have changed.

I’ve always shopped for lighting with the simple idea that watts equal brightness. Of course I know that a watt is a measure of power, but it’s always been true that the higher the wattage, the brighter the bulb. As new lighting technologies become available, it’s important to start associating watts with energy consumption and thinking about brightness using the correct measure: lumens. Lumens are the measure the brightness of light perceived by the human eye.

Watts is generally related to light output but assumes each measure is for the same means of producing the light. That assumption is no longer as valid as it once used to be in regards to household lighting.

Efficiency = Lumens ÷ Watts
– A 60-watt incandescent bulb producing 800 lumens has an efficiency of 13.3 LPW.
– To generate 800 lumens with a CFL will require about 15 watts, with an efficiency of 53.3 LPW.
– Readily available LEDs are comparable with CFLs in efficiency, but have reached ratings as high as 100 LPW.

What happens with new technologies is that the idea can sound great but the implementation uncovers problems. The problems that are uncovered spur development and, over time, the problems are reduced.

Flourescent lighting is an example. It became inexpensive enough for practical household use but there were problems with color and with flickering. Advances in the flourescent coatings used and in the ballast and driving hardware have reduced these problems. Problems with size and custom fixtures have been tackled with the CFL.

Color has been an issue with LED’s, too. Development of LED materials that produce a variety of colors coupled with lighting that combines different color LED’s to obtained a desired color output has pretty much solved that problem. As Collin notes, though, LED’s are still very pricey and they are more directional that the alternatives and this can make even area lighting difficult.

The cost issue is often seen as strictly a capital cost, what you pay for the bulb. Actual costs tend to get buried in the electrical bill. More efficient lighting will pay off over time. For industrial applications where the lights are used daily for long periods, a quick payoff is possible. For home use, where the lights are only only periodically and for short periods of time, the efficiency savings take much longer to achieve a total cost savings.

Technology brings in options. The paradigm shifts. We can’t think just in terms of watts when it comes to getting light in our house anymore. Lighting is getting complicated.

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