Energy consumption: Daylight saving time does have advantages

On the weekend of March 25-26, 2023, the clocks will once again be set forward by one hour. With the annual time change also comes the discussions about whether it should be abolished or not. Opponents argue that the time change brings negative health effects such as sleep disturbances. Advocates of daylight saving time, on the other hand, often put forward the argument of saving electricity. After all, if it's light for an hour longer in the evening, less artificial light is needed. "That was the original intention behind the introduction of the time change. From our point of view, however, it makes sense to look not only at the impact on electricity savings in lighting, but on the overall energy consumption of a building," explains Sven Eggimann. Together with his colleague Massimo Fiorentini and other researchers from Empa's Urban Energy Systems Lab, he has therefore determined whether and how the time change affects heating and cooling energy consumption.

The basic hypothesis of the research team was that office workers are in the office one hour earlier in the summer due to the time change and thus also leave it earlier in the afternoon. Since most of the cooling power is required later in the afternoon, this can save energy. The prerequisite, however, is that the cooling system can be shut down or turned off when the office is empty. This would be easy to achieve in so-called "smart buildings". In many places, however, this is still a long way off.

To test the above hypothesis, the researchers simulated the heating and cooling energy used with and without daylight saving time for different climate regions based on data from various office buildings in 15 US cities. They took into account not only the current climate, but also future climate scenarios up to 2050, in order to include the influence of climate change. This is crucial, because climate change has an enormous impact on a building's energy consumption. In another study, for example, Empa researchers found that in the future Switzerland could have the same demand for cooling energy as for heating energy due to climate change.

The study results are grist to the mill of daylight saving time proponents. "Switching to daylight saving time can reduce the cooling energy of an office building by up to almost six percent. At the same time, heating demand can increase by as much as 4.4 percent due to the earlier start of work in the morning. However, since much more cooling energy is consumed than heating energy in summer, the time change has a positive overall effect on the energy balance of a building," summarizes Massimo Fiorentini. Across the different climate scenarios and climate zones, the energy saved varied - the maximum total energy saving was 3 percent - but it was effective everywhere. Although this result only relates to office buildings in the U.S., it also provides valuable insights for Switzerland, because the climatic conditions are comparable for several of the simulated climate zones.

"Our study shows that the time change can contribute to climate protection. In the discussion about abolishing daylight saving time, political decision-makers should therefore not only consider the electricity savings in artificial lighting, but also the impact on the energy balance of office buildings as a whole," says Eggimann. At the same time, the researchers emphasize that the time change is only one of many ways to influence the energy consumption of an office building. Improvements to the building stock, behavioral changes or a general adjustment of working hours can also contribute to energy savings and thus to CO₂-reduction - regardless of whether the clocks have to be changed or not.

Source: Empa