Daylight Savings Time. Why do we put the clock forward

For decades now, the last Sunday in March marks the beginning of daylight savings time. At 2 am, we move our clocks 60 minutes forward - with electronic devices doing it automatically, without our help! Then, after seven months - on 25 October this year - we do the opposite, and go back to the solar standard time. In this article, we will discover how Terna - the company that manages Italy’s national transmission grid - calculates the benefits of applying the DST for the Italian electricity system, in terms of cost savings and environmental sustainability.

The containment of electricity consumption is a very current issue, but energy efficiency, one of its fundamental components, has now passed the century of life. Indeed, daylight savings time was established in Italy, and in several other European countries, in 1916. Every year, Terna assesses the effects of this measure - by which the daylight savings time is applied between the end of March and the end of October - on Italian electricity consumption, and estimates the financial and environmental benefits for citizens and businesses.

2026 data: lower consumption by 302 million kWh
At the end of March, Terna publishes an estimate of the impact that the application of daylight savings time will have for the following 7 months in terms of lower electricity consumption, and therefore what the saving on energy costs will be for the country and the environmental benefit linked to the reduction of greenhouse gas emissions. For 2026, Terna estimated that in the months in which daylight savings time is in force, from 29 March to 25 October, Italy will save around 302 million kilowatt hours (kWh). To get a better idea, it is as if more than 115K Italian households did not consume electricity for an entire year. Imagine “switching off” an entire city the size of Vicenza, Siracusa or Pescara for all of 2026!

Because we consume a lot less electricity in daylight savings time. Towards the end of March, with the days getting longer (because the Earth’s axial tilt, from December onwards, causes our hemisphere to gradually tilt toward the Sun, with consequently greater sunlight exposure until the beginning of the Summer), many people wake up when there has already been light for at least one hour, while in the evening, artificial lighting is still used for several hours. While with daylight savings time, one hour of natural light is gained, thus reducing the use of artificial lighting in homes, offices, streets and businesses in the evening.

So, how much do we save? From a conceptual standpoint, this calculation is simple: Terna compares electricity consumption before and after the daylight savings time is applied. However, in reality, it is a little more complicated because the change in electricity consumption is linked to various factors: these include the temperature, cloudiness or, for example, holidays and long weekends. Terna’s task is to remove the trend in demand from these elements so that only the effect of the time shift remains. So, in practice, we analyse the electricity consumption recorded in the week before and after daylight-saving time and we apply corrective factors to make them comparable. On the other hand, it is more complicated to estimate the projection of this benefit, which tends to decrease in the weeks following the time change.

In addition to energy, daylight-saving time also brings environmental benefits. Even if the production of renewable sources plays an increasingly important role, the energy that we consume is partly produced by traditional power stations which, using fossil fuels, emit carbon dioxide, which contributes to the greenhouse effect. The application of daylight-saving time makes it possible to use these pollutant sources less and thus reduce CO₂ emissions. Terna estimated that in 2026, thanks to daylight-saving time, about 142,000 tonnes of CO₂ will not be emitted into the atmosphere.

What about the financial benefits? Besides being better for the environment, daylight savings time it is also good for our wallets, as lower energy consumption means lower costs for citizens. The financial savings estimated for the DST period in 2026 has been calculated considering that the average cost of electricity per kilowatt hour for the typical domestic user in the protected market (the user targeted by Terna, according to data from ARERA), and is currently around 26.63 euro cents before tax for the first quarter of 2026. It is easy to calculate that 302 million fewer kWh are the equivalent of 80 million euros.

According to Terna’s analytic data, since 2004, Italy has saved over 12 billion kWh thanks to DST, amounting to approximately 2.3 billion euros saved by Italian citizens. Although it might not look like much, this figure is absolutely massive: 12 billion kWh correspond to the average annual consumption (2024) of the Calabria and Sardegna regions or the Marche and Abruzzo regions combined. It should be noted, however, that energy savings are decreasing from year to year because with the spread of LED light bulbs and many high-efficiency systems, the energy required for lighting or other assets has decreased.

Months during which DST are more evident. The DST months with the higher energy savings are April and October, since they have a “shorter” span of natural daylight than the other months in this period. And so, moving the hands of the clock ahead by one hour postpones the use of artificial light while business activities are still in progress. Instead, during the summer months such as June, July and August, as the days are already longer compared to April, the delay in turning on the lights occurs in the evening when most working activities have ended, leading to less significant results in terms of electricity savings.