Many consumers spent the last two decades swapping out their old incandescent light bulbs for CFLs in the name of greater efficiency. The spiral tubes used less energy, saved money, lasted longer—and people hated them.

Now CFLs, or compact fluorescent lamps, are slowly disappearing from stores. Home retailer IKEA stopped selling them in all its locations last year, and now manufacturer GE has penned a cheeky Dear John letter to the technology, saying it will stop making the bulbs in the United States.

“I can see clearly now that LED is my future,” the letter says, referring to the light-emitting diodes that have gained sales as their prices drop. The latest U.S. numbers show CFL shipments down 28 percent from last year, while LEDs are up a whopping 237 percent, according to the National Electrical Manufacturers Association. And under new U.S. standards proposed Friday, current CFLs won't even be efficient enough to make the cut.

While the prognosis isn’t good, the obituary for CFLs can’t be written just yet.

“They won’t disappear overnight, that’s for sure,” says Terry McGowan, director of engineering and technology for the industry’s American Lighting Association. “I think you’ll find that there will be CFLs around for a long time yet.” He says they do fine as a “low-cost socket filler,” so they will still hold appeal for utility lighting, especially outside the U.S.

Introduced in the mid-1980s, CFLs progressively got cheaper and more efficient, using 75 percent less energy than a regular incandescent bulb. But they never quite overcame the problems that made them unlovable: They needed time to light up fully, the light often felt harsh, and the glass tubes contained toxic mercury, prompting an unsettling cleanup checklist for any poor soul who happens to shatter one.

“You start adding all these things up, and the pendulum just swings over to LEDs rather quickly now. I think that pendulum is going to keep on moving,” McGowan says. In a study funded by the Department of Energy two years ago, LEDs edged out CFLs on environmental benefits. And LEDs, which lack the quality and fragility problems of CFLs, now cost just a fraction of what they did a few years ago. One study notes that LED prices declined between 28 and 44 percent per year between 2011 and 2014.

Some countries, such as India, will take a little longer to transition to LEDs. While North America’s lighting market will be 70 percent LED and 4 percent CFL by 2020, according to a 2012 report from the consulting firm McKinsey & Company, India will be 59 percent LED and 15 percent CFL. Other types, such as halogen (a more efficient version of the incandescent lamp) and linear fluorescent bulbs, make up the rest.

GE says it’s partnering with Walmart and Sam’s Club to promote the shift to LEDs. Others in the industry are following suit. Ace Hardware emphasizes LEDs over CFLs and halogen bulbs on its website. A spokesperson for manufacturer Philips says that while it has a “healthy” CFL business, it is “leading the shift toward” LEDs, and its sales figures reflect the trend.

Some researchers still carry a torch for the incandescents of old, pioneered more than a century ago by Thomas Edison but now phasing out in the U.S. and elsewhere. Last month, scientists from the Massachusetts Institute of Technology and Purdue University described the use of nanotechnology to reduce the heat loss that makes traditional bulbs so inefficient. Others are doing similar work, McGowan says, but they don’t have much time. Any U.S. resurrection of incandescents would have to meet a much stricter standard that goes into effect by 2020.

“It’s interesting that people still keep trying to improve the incandescent lamp product,” McGowan says in an amused tone. “I wish them well.”

McGowan spent 38 years at GE. His friend and colleague there, Ed Hammer, invented the spiral CFL design in the 1970s, redefining the possibilities for fluorescent light. Hammer was seeing LEDs begin to rise before he died in 2012. “Well, they’re gaining on us,” he joked to McGowan of the competition, but he knew CFLs had a good run.

“I think that’s what Ed would say: We’ve had a pretty good run,” McGowan says of the trends. “We’ve done some great things, and we reduced the cost of lighting.”

The story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.