On Nov. 5, most Americans will sigh heavily and turn back their clocks one hour for the end of daylight saving time (DST). Ever wonder why we change our clocks? While some think it is to give farmers an extra hour of sunlight in the evenings during warmer months, DST was implemented as a means to reduce electricity use in buildings. But does daylight saving time actually save energy?
Prior to 1966, DST was occasionally and non-uniformly observed in the USA. After 1966, the federal government signed a law standardizing the observance of the time change. DST rules were subsequently amended by the Reagan administration and most recently by the Bush administration as part of the Energy Policy Act of 2005. These changes allowed DST to remain in effect for a longer period. The rationale behind extending DST is that by increasing daylight hours in the evening, energy usage during those hours will drop since the need for lighting will be reduced.
However, the energy impacts of DST are up for debate. An article from Tufts University suggests that the benefits of DST are not necessarily related to energy savings. The post points out that recent studies have shown minimal reductions in energy usage, and that a new large-scale study actually demonstrated a 1%-4% rise in usage as a result of DST. One reason for this trend could be that greater demand for air conditioning in the evenings offsets reductions in usage from lighting. The post also points out that gas consumption due to automobile traffic increases during DST since people are more likely to drive to other locations after work as a result of increased daylight hours, resulting in greater carbon dioxide emissions.
Although the energy impacts of DST are minimal, several industries benefit from more daylight hours in the evening and have lobbied to expand DST. According to the Tufts post these industries include the barbeque grill and charcoal industry, the golf industry, and the gas industry.
Another non-energy benefit is much harder to quantify: human happiness caused by daylight after the work day is over.