California Banned the Incandescent Bulb to Save Energy. It Cost Something Else.

In 2020, the most sleep-friendly light source on the American market quietly disappeared from California's shelves. Six years on, the data on what replaced it is starting to tell a story no one prepared us for.

The first day of 2020 was, in most ways, an ordinary day in California. The state's hardware stores opened on time. The lighting aisles were stocked. The packaging on the bulbs looked roughly the same as it had the week before.

But something had changed.

If you had walked into a Home Depot in Sacramento, or an Ace Hardware in Pasadena, or a corner electrical supply store in Oakland on that first morning of the new year, you would have noticed — if you looked carefully — that one particular kind of light bulb was no longer on the shelf. The standard incandescent bulb that had lit American homes for more than a century was gone. Not phased out gradually. Not put on a clearance rack. Just gone.

In its place were rows of LEDs. Some labeled "soft white." Some labeled "daylight." All of them legal under the new state efficiency standard that had taken effect at midnight. None of them carried any label indicating what they would do to the people living under them.

That morning, California became the first state in the country to enforce a lighting standard that effectively removed the traditional incandescent bulb from store shelves. The rule, known as Title 20, was framed as a victory for energy efficiency. It was a long time coming. It had been the subject of legal fights, industry pushback, and federal-versus-state preemption battles. By the time it finally took effect, most Californians were not paying attention.

And so the change happened quietly, on a Wednesday, in the way that consequential changes often happen — without protest, without ceremony, and without any obvious warning of what came next.

What the State Was Trying to Do

The intention behind Title 20 was reasonable. The case for it was, in retrospect, almost unimpeachable. Incandescent bulbs are spectacularly inefficient at producing light. A standard 60-watt incandescent generates about 15 lumens per watt of electricity it consumes; an equivalent LED produces 75 lumens per watt or more. Across a state of 40 million people, the difference adds up to billions of kilowatt-hours and several billion dollars in avoided utility costs over the life of the rule. The California Energy Commission projected savings somewhere between $736 million and $2.4 billion. Carbon emissions would drop. Power demand would ease. The grid would breathe.

These projections were not exaggerations. They have, by and large, been borne out.

The rule's text was technical and narrow. To comply, a general-service bulb sold in California had to produce at least 45 lumens per watt of electricity. It had to render colors with reasonable fidelity (a Color Rendering Index of at least 80). It had to last at least 1,000 hours. It had to fall within a Correlated Color Temperature range of 2200 to 7000 Kelvin.

Those were the criteria. Read carefully, they are striking for what they include — and for what they leave out.

Every one of those metrics measures either how much electricity a bulb uses, how long it lasts, or how it appears to the human eye. Not one of them measures what the light does to the human body that lives under it.

This is the gap.

The Bulb That Disappeared

To understand what California removed from its shelves on January 1, 2020, it helps to understand a basic fact about how light interacts with the human body — a fact that was already well-established science by the time the rule took effect, but which the rule itself made no attempt to address.

Humans, like nearly every animal on Earth, have an internal clock. The clock runs on a roughly 24-hour cycle. It governs when we get tired, when we wake up, when our cortisol rises, when our digestion is most efficient, and when our cells perform the maintenance work that keeps the body running over decades. The clock is set, primarily, by light.

Specifically, by a narrow band of blue light — wavelengths between roughly 440 and 495 nanometers, with peak biological sensitivity at around 480 nanometers. Light at those wavelengths, hitting the eye, signals to the brain that it is daytime. The brain responds by suppressing the release of melatonin, the hormone that initiates sleep.

This is not theoretical. This is two decades of published research, replicated in laboratory after laboratory, summarized in peer-reviewed consensus documents from Harvard, Oxford, Munich, and Manchester.

The light from a traditional incandescent bulb sits almost entirely outside this band. The bulb works by heating a tungsten filament, which glows with a warm, red-shifted light overwhelmingly weighted toward the long-wavelength end of the visible spectrum. In recent peer-reviewed measurements published in Nature in 2026, traditional incandescent lamps produced a Melatonin Suppression Value of approximately 1.5 percent — the lowest score of any common indoor light source ever measured.

The light from a standard cool-white LED — the kind that now fills the shelves of every California hardware store — produced an MSV of approximately 12.3 percent. More than eight times the biological signal of the bulb it replaced.

Same room. Same brightness to the eye. Eight times the message to your brain that it is still daytime.

And the variation does not stop there. Even within the LED category, research published by Dr. Martin Moore-Ede in 2021 documented a more than five-fold difference in nocturnal melatonin suppression between different LED light sources delivering identical brightness — depending entirely on how much energy each one emits in the 440-to-495-nanometer band. Two LED bulbs sitting next to each other on the same hardware store shelf, both fully compliant with California law, can have radically different effects on the body's ability to prepare for sleep.

The label on the box tells the consumer none of this.

What the Doctors Tried to Say

None of this was unknown at the time California passed Title 20. The science was old. The warnings were on the record.

In 2016 — four years before the rule took effect — the American Medical Association issued a formal policy statement on the health consequences of blue-rich LED lighting. The statement warned that high-blue-content LEDs operate at a wavelength that adversely suppresses melatonin at night. It noted that surveys had already begun linking brighter residential nighttime lighting to reduced sleep duration, dissatisfaction with sleep quality, excessive daytime sleepiness, impaired daytime functioning, and obesity. It recommended that outdoor LED lighting be limited to a Correlated Color Temperature of 3000K or lower — a temperature considerably warmer than the cool-white LEDs that now dominate residential interior lighting.

The AMA statement was, in retrospect, prophetic. It was also widely ignored in the policy world.

The same year, the city of Davis, California — a college town of about 70,000 people roughly 15 miles west of Sacramento — became one of the first communities in the United States to publicly revolt against the consequences of LED policy. The city had recently installed high-color-temperature LED streetlights as part of an energy upgrade. Residents complained. The light, they said, was harsh. It leaked into bedroom windows. It was harder to sleep with the new lights in the neighborhood. The complaints became loud enough, and persistent enough, that Davis ultimately agreed to do something almost unheard of in municipal lighting policy: replace the streetlights it had just paid to install.

The Davis story made national news. It was cited by the AMA. It was cited by sleep researchers. It was cited by lighting industry critics. And four years later, the state of California — having paid attention to the energy implications of LED policy but apparently not to the biological ones — passed Title 20.

What Has Happened Since

It would be useful, here, to report that a major public-health body has formally studied California's sleep data in the years since Title 20 took effect, comparing it against pre-2020 baselines or against other states. It would be useful to report on a population-scale natural experiment that has been thoroughly analyzed by an independent research institution.

No such study has been published. The data exists — in private databases at companies like Oura, Apple, and Fitbit, which collectively track the sleep patterns of tens of millions of Americans every night — but it has not been analyzed for this purpose. Whether California sleep quality has changed in measurable ways since January 2020 is, at present, a question the public-health establishment has not formally answered.

What has been published, however, is a national picture of American sleep in the same window — and the national picture has degraded sharply.

According to the U.S. Centers for Disease Control and Prevention, roughly one-third of American adults reported short sleep duration in 2020. About 14.5 percent reported trouble falling asleep most days or every day. Almost 18 percent reported trouble staying asleep. These are not subtle numbers; they describe a country in which sleep, as a basic biological function, is failing at scale.

The Gallup organization, which has tracked American sleep self-assessment for two decades, found in December 2023 that only 36 percent of American women said they were getting the sleep they needed — the lowest figure Gallup has ever recorded. The same poll showed double-digit declines from previous readings across nearly every adult age group. These were among the steepest single-decade drops in American sleep self-assessment on record.

There are, of course, many causes for the American sleep crisis. The pandemic disrupted sleep schedules. Screen time has risen. Anxiety has risen. Phone use in bed has become near-universal. Caffeine consumption is at all-time highs.

The relevant question is not whether LEDs alone caused the decline. They almost certainly did not. The relevant question is whether the wholesale transition of the American indoor lighting market — from less than 1 percent LED in 2013 to more than 80 percent LED by 2022, accelerated in California by force of law in 2020 — could plausibly have contributed to it.

The biology says yes. The biology is, in fact, unambiguous on the point. If the lighting in your home shifts toward sources that emit eight times the melatonin-suppressing signal of the lighting you used to live under, the most likely consequence is that your body's sleep-preparation hormone gets suppressed more often, by more, for longer. Whether that translates into a measurable population-level effect depends on dose, on timing, on individual variability — but the direction of the effect is not in dispute.

The Longer Question

Sleep is not the only thing the circadian system regulates. It is the most visible thing — the symptom most people can feel — but the underlying system extends much further.

The same internal clock that controls when you fall asleep also regulates the release of growth hormone during the night, the consolidation of memories from short-term to long-term storage, the clearance of cellular waste products from the brain through the glymphatic system, the regulation of insulin and blood sugar, the timing of immune cell deployment, and the daily rhythms of nearly every organ system in the body.

When circadian timing is chronically disrupted — by shift work, by jet lag, by mistimed light exposure — the medical literature documents associations with a wide range of long-term health outcomes. These include cardiovascular disease, metabolic dysfunction, weight gain, mood disorders, and accelerated cognitive aging. The associations have been documented for decades. They are not controversial in the sleep research community, even as the precise mechanisms continue to be studied.

The relevant point here is not that any one person's lightbulb is causing any one outcome. The relevant point is that the regulatory framework that put cool-white LEDs into every American home in the 2020s was designed entirely around energy metrics and made no provision for the long-term biological consequences of the light it required.

The downstream effects of that decision will not be visible in five years. They will become visible — if they become visible — in fifteen or twenty, in the form of population-scale data on cognitive decline, sleep disorders, and metabolic disease in the cohort of Americans who came of age, or aged into their sixties and seventies, under the new lighting standard.

The Federal Echo

What happened in California in 2020 was not the end of the regulatory story. It was the beginning of it.

On April 12, 2024, the U.S. Department of Energy finalized a federal rule that closely mirrors California's standard. The federal rule, scheduled to take effect on July 25, 2028, raises the national efficiency floor from 45 lumens per watt to 120 lumens per watt — a threshold that effectively eliminates not only incandescent and halogen bulbs but most compact fluorescent bulbs as well. After that date, the residential lighting market across the United States will consolidate almost entirely around LEDs.

The federal rule, like California's, contains no provision regulating the spectral content of compliant light sources. It optimizes for energy efficiency. It does not address biology.

During the federal rulemaking process in 2022, public commenters raised concerns about the human health consequences of the LED transition. The Department of Energy responded by stating that it "had not found any evidence that using LEDs in daily life directly results in adverse health effects." This statement was issued despite the AMA's standing policy, despite twenty years of published research on circadian disruption, and despite a 400-page report on LED health effects published by the French Agency for Food, Environmental, and Occupational Health and Safety in 2019. The DOE did not refute the science. It declined to engage with it.

What California did in 2020 with 40 million people, the federal government will do in 2028 with 330 million. The blueprint is the same. The blind spot is the same.

The Bulb That Was Already Engineered

There is one residential light bulb on the American market today engineered specifically to fill the gap the regulators left.

It is called the OIO Bulb. It is made by Korrus, a Los Angeles–based lighting research company that has been working on the problem of biologically aligned light for the better part of a decade. Korrus is supported by Dr. Martin Moore-Ede, the Harvard-trained physiologist whose 2020 research established the 477-nanometer peak sensitivity that underpins much of the published melatonin-suppression literature cited earlier in this article. The company's scientific team has spent years on a single question: what would a light bulb look like if it were designed for the human body instead of around it?

The answer turned out to require a different starting point than the rest of the industry uses.

Every standard white LED on the market — the ones now filling California's shelves, and the ones the rest of the country will be buying after 2028 — begins with a blue LED chip emitting at roughly 450 nanometers. That is, almost exactly the wavelength of maximum melatonin suppression. A yellow phosphor is then added to round out the spectrum and make the light appear white. Every bulb built this way carries the original blue spike inside it. "Warm white" versions reduce the spike. They do not remove it.

The OIO Bulb does something different. It begins with a chip that emits at around 410 nanometers — violet light, which sits below the melatonin-suppression band entirely. Phosphors then complete the spectrum, producing a light that renders colors faithfully, looks pleasingly white to the eye, and emits less than 2 percent of its energy at the wavelengths that suppress melatonin. In side-by-side comparison, OIO produces approximately 68 percent more circulating melatonin in the evening hours than a standard LED of equivalent brightness.

It screws into a standard E26 socket. It meets the federal 2028 efficiency standard. It does not require a special fixture, a special app, or a custom installation.

It is, at present, the only consumer light bulb in the United States built on this architecture. It is the answer the regulation should have written into the rule.

The Choice That Still Exists

For Californians, the change has already happened. The lighting available in your state since January 2020 has been almost entirely composed of bulbs whose biological effects on your sleep and your long-term circadian health are not regulated by the law that put them on your shelves. Six years of lived experience have already accumulated under the new regime.

For the rest of the country, the same conditions will apply by federal mandate in July 2028.

There are, in practical terms, three responses available to an individual reader.

The first is to do nothing — to let the regulatory framework continue to define the lighting available in your home, and to assume that the regulators have considered every relevant variable in setting the rule. This is what most consumers will do. It is what most consumers in California did in 2020.

The second is to stockpile traditional incandescent bulbs while they remain available in narrow specialty categories. This is a short-term workaround. Manufacturing of these bulbs is shrinking, the exemptions are subject to revision, and stockpiling postpones the problem rather than solving it.

The third is to actively seek out lighting that meets both the energy-efficiency standards the law requires and the biological standards the law omits. This is, today, a small market. It requires looking past the labels and packaging that fill the lighting aisle. But the technology to do this exists, has existed for several years, and is now available to ordinary consumers without prescription, special expertise, or a custom installation.

What ended on the first day of 2020 was the era in which American homes were lit, by default, by the most circadian-friendly common light source ever sold in the country. What began on the first day of 2020 was the era in which Americans, if they want that quality of light, have to choose it on purpose.