We already know that incandescent light-bulbs are on the way out because they're incredibly wasteful, being better at producing heat than light. And most people know that LEDs have started replacing compact fluorescents (CFLs) and should become the next gold standard for producing light. But are LED bulbs truly better than CFLs? If so, by how much? To really know, it's not enough to just look at lumens-per-watt efficiency; you have to do a full life-cycle analysis to truly figure out which one comes out on top when everything is taken into account — including manufacturing, usage, transportation, how many bulbs are used over time for those that don't last as long, etc.

That's what the U.S. Department of Energy did in this very thorough analysis, and the agency's findings are interesting.

LED and CLF bulb compared

Graphic: U.S. Department of Energy

The graph above summarizes the result of their tests:

“The average life-cycle energy consumption of LED lamps and CFLs are similar, at approximately 3,900 MJ per 20 million lumen-hours. This is about one quarter of the incandescent lamp energy consumption — 15,100 MJ per functional unit. By 2015, if LED lamps meet their performance targets, their life-cycle energy is expected to decrease by approximately one half. In addition, based on this analysis, the 'use' phase of incandescent, compact fluorescent and LED lamps is the most energy intensive phase, on accounting for approximately 90 percent of total life-cycle energy. This is followed by the manufacturing and transport phases, respectively with transport representing less than one percent of life-cycle energy for all lamp types.”

Incandescent, LED and CLF bulb compared

Graphic: U.S. Department of Energy

So CFLs and LEDs are about the same on an LCA basis right now, though there are other reasons why one might want to pick LEDs. For example, LEDs are less fragile than CFLs, and they don't release mercury when broken, they last about three times longer, and they turn on more quickly.

But the real leap forward will come in about two years when next-generation LEDs come to market. We've written about one by Philips that gets 200 lumens/watt. These should be about twice as good as current LEDs and CFLs, allowing LEDs to finally declare a decisive victory over fluorescents.

Related on MNN:

Michael Graham Richard ( @Michael_GR ) Michael writes for MNN and TreeHugger about science, space and technology and more.