Daylight-saving time found to cut energy usage in office buildings

Scientists have calculated that daylight-saving time (DST), which starts on Sunday, cuts the energy consumption of office buildings throughout the summer.

While DST opponents often argue that the time change impacts our health, for instance through sleep disturbances, proponents make the case that electricity can be saved because of longer days, which means that less artificial light is needed.

“That was the original intention behind the introduction of daylight saving. 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,” explained Sven Eggimann from Swiss research organisation Empa.

During DST, employees start their work an hour earlier in summer due to the time change, and thus leave the office earlier in the afternoon.

Since most of the cooling happens later in the afternoon, this can save energy. The assumption behind this is that in an empty office the cooling can be reduced or even turned off completely. As buildings become more intelligent, this would be relatively easy to accomplish in the future.

To test the hypothesis, the researchers simulated the heating and cooling energy used with and without daylight-saving time for different climatic regions based on data from various office buildings in 15 US cities.

In order to include the influence of climate change, they took into account not only the current climate, but also future climate scenarios up to the year 2050 as this is expected to have an enormous impact on a building’s energy consumption.

“Switching to daylight-saving time can reduce an office building’s cooling energy by up to almost 6 per cent. At the same time, heating demand can increase by up to 4.4 per cent due to the earlier start of work in the morning. However, since much more cooling than heating energy is needed in summer, the time change has a positive overall effect on the energy balance of a building,” researcher Massimo Fiorentini said.

Across the different climate zones and scenarios, the overall energy savings varied – peaking at around 3 per cent – but they were evident everywhere.

“Our study shows that the time change can contribute to climate protection. In the discussion about eliminating daylight-saving time, policy 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,” Eggimann added.

The researchers said that while the time change influences the energy consumption of a building, it is not the only way. Other efforts include technical improvements of the buildings, behavioural changes and a general adjustment of our working hours.

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