Yesterday, the clocks changed in many parts of the world. For most of us, the process was considerably easier than it once was: our phones, laptops and smartwatches quietly adjusted themselves while we slept. The oven clock and that slightly inconvenient clock high on the kitchen wall may remain on the old time for several more days—or possibly until the clocks change again. But not every country changes its clocks, and in those that still do, the practice is increasingly questioned. So why do we continue doing it?

Originally, there was a clear economic rationale for changing the clocks twice a year. As the days became longer, moving the clocks forward shifted an hour of daylight from the early morning—when much of the population was still asleep—to the evening, when people were more likely to be working, shopping, socialising or taking part in leisure activities. In economic terms, the aim was to reallocate a limited natural resource—daylight—from hours when it generated relatively little benefit to hours when it could produce greater consumer satisfaction, economic activity and social value. If homes and workplaces remained naturally lit for longer during the hours in which they were being used, they would also require less artificial lighting. This could lower household and business energy costs, reduce overall demand for electricity and limit some of the environmental costs associated with energy production. Changing the clocks therefore appeared to provide a simple coordination mechanism: by moving everybody’s schedule together, society could make more productive use of the available daylight while reducing both private energy expenditure and wider social costs.

However, the way in which we consume energy has changed considerably. Artificial lighting once represented a much larger proportion of electricity consumption, while modern lighting—particularly LED bulbs—uses far less energy. Heating, air conditioning, computers, appliances, data centres and services operating around the clock now account for a greater share of demand, and their energy use is not determined simply by whether it is light outside.

Moving an hour of daylight may reduce the need for lighting in the evening, but it can also increase heating use during darker mornings or air-conditioning use during brighter, warmer evenings. The clock change may therefore alter when energy is consumed without substantially reducing the total amount.

This changing evidence is at the centre of a recent European Union policy document. Published in October 2025, it argues that the energy-efficiency justification for changing the clocks has largely disappeared. The document cites a meta-analysis drawing together 162 estimates from 44 studies. Although the simple average suggested a very small reduction in electricity use, the researchers’ preferred estimate placed the saving at approximately 0.01%—effectively zero. The document therefore calls for governments to reconsider whether the twice-yearly disruption remains justified when one of its principal original benefits can no longer be clearly identified.

Nevertheless, the disappearance of meaningful energy savings does not necessarily eliminate the entire economic argument. Moving daylight towards the evening may still increase consumer satisfaction by allowing more people to exercise, shop, meet friends or participate in leisure activities after work or school. It may also support businesses in retail, hospitality, tourism and outdoor recreation.

The energy-saving argument may have weakened, but the potential benefit of allocating daylight to the hours when people value it most remains. The unresolved question is whether that gain from reallocating daylight is large enough to compensate for the inconvenience, disruption and other costs of changing the clocks twice every year.

Reference

Council of the European Union (2025), The Need to Address Daylight Saving Time Given the Absence of Energy Efficiency Gains, 20 October 2025, Document 14195/25.