Climate Action
Falling Back on Daylight Saving Time
November 2, 2025
With fall upon us, Daylight Saving Time (DST), is coming to an end today. You may have woken up feeling extra refreshed, as many states across the U.S. — and countries around the world — gained an extra hour of sleep. This contrasts with the start of DST in the spring, when we lose an hour of sleep in exchange for brighter evenings.
DST was originally introduced with the intention of saving electricity. The idea was that by shifting the clock forward in spring, people would have more daylight in the evening, reducing the need for artificial lighting and therefore conserving energy. However, there have long been debates about its true effectiveness — while it may reduce electricity use later in the evening, it can also increase energy demand on darker, cooler mornings.
Another often-mentioned benefit of DST is that it can help reduce symptoms of seasonal affective disorder (SAD) by extending daylight exposure during waking hours. Still, with so many pros and cons, it raises an ongoing question: should Daylight Saving Time continue to be observed?
Colder Mornings, Hotter Evenings
Daylight Saving Time first began in Germany and Austria in 1916. With resources under pressure during World War I, it was intended to conserve the fuel needed to produce electricity, until later in the day. The United States later adopted the idea in 1918.
However, while DST may reduce electricity use in the evenings, for early birds, the darker mornings will require more electricity use, for lighting and heating. Additionally, longer daylight hours, accompanied by warmer temperatures in the summer, may increase air conditioner use for longer and later periods of the day in parts of the world, like in the U.S., where many rely on air conditioning.
The true benefits of saving daylight can also vary in different regions. For example, in Southern Norway and Sweden from 2003 to 2009, it was found that DST reduced electricity consumption by at least 1%, saving 16.1 million Euros for consumers in Southern Norway and 30.1 million Euros for consumers in Sweden annually.
On the contrary, for hotter areas such as Arizona in the United States, DST can actually increase electricity use. Arizona only observed DST for less than one year, discovering that the jump forward in time caused individuals to run their air conditioning for longer in the evening. Since different parts of the world receive different amounts of sunlight depending on their geographic regions, the ability of DST to save electricity consumption varies by region.
Summer Fun and Winter Blues
Falling back in time once DST comes to an end each November can trigger seasonal affective disorder (SAD) for many people , especially when the weather gets colder in the winter. Also referred to as seasonal depression, the condition affects on average up to 10% of northern regions of the U.S. but only 1% of southern regions as of 2021. Typically, northern regions of the U.S experience more intense winters with colder temperatures.
Seasonal depression is closely linked to changes in the circadian rhythm, which is the sleep/wake cycle caused by the rising and setting of the sun. The shorter daylight hours in the winter can cause a cycle of low energy and listlessness. While seasonal depression can occur in the summer, it is less common.
On the contrary, the warmer weather and more daylight in the evenings in the spring and summer can sometimes boost moods. Exposure to natural sunlight can produce serotonin, which helps regulate mood and promote feelings of happiness. Additionally, the extended daylight can encourage people to participate in activities later in the day, especially after work. People may spend more time outdoors playing sports, taking kids to the playground, and going on walks. Increased physical activity is often associated with boosting moods and overall well being.
However, this increase in human activity can also have unintended consequences, such as releasing more carbon emissions as people drive their cars later in the day to go to parks, events and activities.
Sleep and Safety
When the clocks spring forward at the start of DST, many of us feel fatigued from the loss of an hour of sleep. This effect doesn’t only last for the first day of DST; studies have shown that pushing clocks forward can have longer term detrimental health effects.
A study done in 2020 showed that the rate of car accidents rises by 6% following the switch to DST. The Monday after DST begins often has a 24% increase in heart attacks. The week after DST shows an associated increase in cardiovascular disease, mental health and cognitive issues, and digestive and immune-related diseases. It is estimated that getting rid of DST would prevent about 300,000 cases of stroke per year and result in 2.6 million fewer people having obesity.
When you lose an hour of sleep, it disrupts your internal clock because you wake up before your body is ready to. This disruption often lasts for the remainder of DST, ultimately decreasing the amount of sleep you get each night. This can result in behavioral, learning, and attention issues in adolescents and a greater risk of high blood pressure and diabetes for all ages.
Additionally, your circadian rhythm relies significantly on exposure to light. When there is less light exposure in the morning, it can actually decrease serotonin levels. And in the evening, the increased exposure to sunlight can delay the production of melatonin, which is needed to help you fall asleep.
To Save or Not to Save?
While the true amount of energy saved during DST varies regionally, it is undeniable that energy use should be conserved to limit the amount of carbon emissions released from electricity generation. One way to offset the emissions from energy without completely cutting down on energy use is to rely more on renewable energy sources.
This year, Earth Day’s 2025 theme is OUR POWER, OUR PLANET™. Regardless of your stance on how DST saves or expends energy, it is undeniable that a switch to renewable energy is needed to limit greenhouse gas emissions. This Earth Day 2025, let’s focus on switching to renewable energy sources to create a sustainable and equitable future.
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