After reigning for more than a century, the once-mighty incandescent light bulb was forced to relinquish its socket throne earlier this month.
The coup, more than 16 years in the making, took place on August 1, when the Biden administration finally implemented a long-delayed rule under the 2007 Energy Independence and Security Act. The rule effectively bans the sale of most (but not all) types of incandescent bulbs, the classic hot-air-balloon-shaped design that has illuminated so much of the planet since the days of Thomas Edison.
The new monarch is the light-emitting diode, or LED, and it’s poised to have an enduring reign. Over the past decade, scientists, engineers, designers, and policymakers groomed the LED to rule, coaxing it to do everything an incandescent could do, but with a fraction of the energy. An LED bulb provides the same amount of light as an incandescent while using 90 percent less electricity and lasting 25 times longer. The 2014 Nobel Prize in physics went to the scientists who invented the blue LED.
“This is absolutely an Edison-level revolution in lighting technology,” said Morgan Pattison, president of Solid State Lighting Services and an adviser to the US Department of Energy’s lighting research program.
Beyond mimicking its predecessor, LED technology brings a whole new suite of capabilities and could let us rethink our entire relationship with light. LEDs are inherently dimmable. They can integrate into surfaces directly, turning walls and ceilings into light sources. Their power consumption can still fall further too.
But one of the LED’s most important traits is its tunability, in both light and color. Optimizing the shade and scope of light rather than blanket illumination could improve safety, productivity, comfort, and health. We’re only beginning to grasp the possibilities.
“LED lighting has outstripped our understanding of how to use lighting in general,” said Pattison. “Instead of just blasting a place with light, we can be more precise in the delivery of light.”
This increased control over illumination may end up being the biggest practical impact of LEDs. They not only provide more light at a higher quality with a lower energy cost, but they can help restore the twilight and dark lost to our overlit world.
How LEDs dethroned the incandescent bulb, and how they can expand their empire of light
Why was it so hard to change a light bulb? The incandescent lamp had a couple big things going for it: It was simple and cheap. It works by passing an electric current through a filament in a vacuum bulb, causing the filament to heat and glow.
The LED, invented by Nick Holonyak Jr. in 1962, is a bit more complicated. It lights up when an electric current passes through a semiconductor diode. A diode is essentially a check valve or one-way lane for an electric current. A light-emitting diode uses a specialized semiconductor material that emits light as electrons flow through it.
These specialized materials raised the cost of early LEDs and limited their performance compared to incandescents. LEDs also don’t produce white light on their own. A white LED requires blending several different LED colors or it needs a material called a phosphor that absorbs light at one wavelength and emits it in another. LEDs often need a driver, a device that converts high-voltage alternating current from a wall outlet into a direct current at a lower, more usable voltage.
However, because LEDs produce light without producing much heat, they have an inherent advantage over incandescents. Only about 10 percent of the electricity used in incandescent bulbs is converted into light. The rest is wasted as heat.
Over the decades, engineers chipped away at the cost and performance gap between the two lamps, and LEDs have slashed energy consumption wherever they’ve been used to replace conventional lights. In 2005, a commercial building would spend about 40 percent of its electricity on lighting. “It’s now down somewhere between 6 and 8 percent,” said Mark Lien, president of Augmented Illumination and a consultant to the Illuminating Engineering Society.
In the lighting industry, the key metrics are efficiency and efficacy (though these terms are often conflated). Lighting efficiency is the amount of light emitted from a fixture as a portion of the total amount of light from a bulb or other light source, usually expressed as a percentage. Luminous efficacy is the amount of light from a source produced for a given amount of electricity. It’s usually measured in lumens per watt.
Incandescent bulbs typically shine around 17 lumens per watt. And because they usually cast just one shade of light, incandescents are either on at full blast or they’re completely off unless they have a specialized dimming fixture or additional electronics. That means light often goes to waste while still being inadequate for the task at hand.
On the other hand, LEDs on the market right now can produce about 70 lumens per watt. High-performance LEDs can get to 170 lumens per watt, and the Energy Department said in 2017 that “a target of above 200 lumens per watt is achievable.” Along with their broader color spectrum and dimming capabilities, LEDs add up to a much more versatile lighting option than hot filaments in glass jars.
Yet from a business perspective, further improvements start to yield diminishing returns. “We could achieve upwards of 400 lumens per watt,” Lien said. “But the market has accepted price and performance levels now.” Going from a 60-watt incandescent bulb to a 10-watt LED is a huge practical improvement, but going from a 10-watt LED to a 5-watt one may not be enough to justify additional costs for buyers, nor the extra research and development from manufacturers.
However, Lien argues that these smaller improvements are still needed because overall electricity demand is growing and the window for limiting climate change is closing. As more electric vehicles charge up and as appliances switch from gas to electric, cutting power demand elsewhere is a key part of balancing the power grid. And given the ubiquity of lights, tiny improvements can add up to huge energy savings.
According to the United Nations, lighting accounts for 15 percent of global power consumption and 5 percent of greenhouse gas emissions, while the International Energy Association notes that LEDs currently account for half of global residential lighting sales. If there isn’t a bigger switch to more efficient lighting, the UN estimates global electricity use for lighting will rise by 60 percent by 2030.
LEDs can gain ground in other traits as well. The lights can continue to scale down in size and switch to more recyclable or biodegradable materials. In applications like TV and computer monitors, LED technology is simply getting better, and the LEDs that power many displays could soon yield to quantum dot LEDs. These nanometer-scale particles integrated into a thin film promise better color, contrast, and viewing angles while lowering power consumption.
There are other technologies in addition to LEDs that could also gain ground in the coming years, but they either aren’t as versatile or are still in their early stages of development. Laser diode lighting, for instance, uses a diode to produce a coherent beam of light. It can handle higher power than conventional LEDs and could provide illumination over long distances in applications like car headlights or lighting sports fields, though costs remain high.
So LEDs are likely to endure for decades, but in forms that we have yet to imagine. “They won’t be the LEDs we’re looking at today,” Lien said. “They will evolve into a much smaller state, perhaps not even recognizable as the sources we have now. You’ll be able to weave them into fabrics, you’ll be able to integrate them into thin films.” So rather than using lights as discrete appliances, illumination could become an integral part of walls, ceilings, sidewalks, and clothes.
The LED imperium will share power with the dark
The transition of power from incandescents to LEDs could have benefits beyond light fixtures and display screens. A century of rapidly spreading illumination has added more hours to the day, with vast benefits for productivity and human development, but it has turned darkness into a precious commodity. Light pollution is growing, with consequences for our bodies that scientists are only now starting to understand. Here, LEDs could also prove valuable.
The body has two distinct pathways that process light, George Brainard, director of the light research program at Thomas Jefferson University, explained in an interview. One is the visual system that consciously processes illumination and color from the environment. Much of the lighting in the modern world is geared toward maximizing the light available to our conscious vision, but that could have unintended consequences.
“Something we’re less conscious of is the fact that light coming into the eye stimulates a different pathway that regulates biology, behavior, and, ultimately, health,” Brainard said. “More specifically, light is driving circadian regulation, hormonal regulation, and neural-behavioral responses.”
Because this pathway is beneath our conscious perception, it’s hard for individuals to gauge how light is changing their sleep-wake cycle, moods, and overall health. But the effects could be profound. There’s already evidence that exposure to blue light from phones, tablets, and televisions in the evening can make it harder to fall asleep and stay asleep. The broader use of artificial light indoors and outdoors could be even more impactful.
Astronauts aboard the International Space Station might provide a useful case study: It’s hard to imagine people more untethered from natural lighting than those that see a sunrise every 90 minutes. Many astronauts have had to use drugs to help them sleep, but space agencies are concerned about the long-term effects of these medicines as stays have grown from weeks to months.
Brainard is working with NASA to study the effects of shifting from always-on fluorescent lights to adjustable LEDs in much of the space station. “It has indeed improved the visual environment for the astronauts, which was one of the two goals, and we are in the process of studying its effects on sleep and alertness and other biological responses,” Brainard said.
For the rest of us on the ground, there may be applicable lessons for school children, shift workers, or patients with long hospital stays, people who often have to wake up and see lights outside typical day and night cycles. And there is a growing body of research showing that exposure to some types of artificial light can contribute to problems like obesity, sleep disruption, anxiety, and high blood pressure. Meanwhile, lighting is already used as therapy for seasonal affective disorder and depression.
But it will take years to measure how much of a benefit we’ll see from switching to LEDs and tuning illumination in the real world across a wide population. “It will be decades of data shaking out,” said Brainard.
So how can we deploy LEDs more intelligently now?
One way is to think about getting lights more in line with natural lighting cycles. “It’s just getting lifestyles aligned with what we already know,” said Mark Rea, a professor in the Light and Health Research Center at the Icahn School of Medicine at Mount Sinai. “If I could oversimplify it, it boils down to bright days, dim evenings, and dark nights.”
It also helps to think about lighting less in terms of how much falls on walls and desks and more in terms of how much is in our vision. “The amount of light at the eye is the most important thing,” Rea said. Optimizing and calibrating lighting based on what hits eyeballs instead of flooding a room could help reduce the total amount of light needed while making it more effective. LEDs are dimmable, so with the right fixture, they offer the opportunity to create a “microlighting environment” where a worker, student, or patient could tune the level of illumination to what is most optimal for them.
Outdoors, LEDs could dim and light up when someone walks or drives by instead of bathing every street with a ubiquitous glow. They could also change their color temperature from cool white during the day to amber in the evening. Curbing outdoor light pollution stands to improve health as well.
The future of lighting, then, is not just a drive toward getting the most light for the least energy, but rather getting the right amount of bright and dark, in the right color, at the right time. It’s a future where we can still save electricity and improve our quality of life, helping us all get more done in the day and sleep better at night.