QUESTION: Does daylight saving time actually result in substantial energy savings? Other countries have done away with it because, as I understand it, the evidence is tenuous. What do you think? Asked by Stella Aslibekyan, Ann Arbor, Mich.
We’ve probably all heard the complaint that Daylight Saving Time is an outmoded practice, leftover from an age when Americans spent their mornings working in the fields, not fighting traffic. But that’s not true—farmers have traditionally been opponents of Daylight Saving Time (DST), and “spring forward, fall back” actually began as a wartime energy conservation measure. The perception that DST saves energy by synchronizing human activity and available daylight hours is often cited as one of its main benefits. During the California Energy Crisis in the early 2000s, the state even requested federal approval to move to a year-round DST. But does fiddling with every clock in your house twice a year really save energy?
Let’s take a trip over to Indiana to find out. The state has a complex history with DST: until April 2006, Indiana was split in half, with only the western side of the state observing DST. Indiana’s late adoption of uniform daylight saving time created a natural study population. By looking at the monthly billing data for the vast majority of southern Indiana households over three years around the switch to state-wide DST, the National Bureau of Economic Research, found that DST actually increased energy expenditure by 1 percent. Most of the increase happened in the fall, when energy demands rose by 2 to 4 percent as people powered up their furnaces an hour earlier in the morning. In all, the Bureau study projected that DST cost Indiana households an extra $9 million in energy bills every year, and generated a cost of between $1.7 and $5.5 million in pollutant emissions. Whatever lighting energy might be saved by DST, the practice’s opponents say, is counterbalanced by increased demand for heating and cooling.
But does the Indiana experiment apply to the rest of the country? Not according to the California Energy Commission (CEC), the Golden State’s main energy policy agency. Heating and cooling requirements differ widely between regions, after all. Compared to Indiana, California heats less in the winter, and air conditions more in the summer. And day-to-night variation in temperature is quite pronounced in California: any Stanford alum knows that even if you go to your afternoon class in a T-shirt, you’ll often want that jacket and scarf when you re-emerge a couple hours later. But California conducted its own study of DST effects when, in 2007, daylight saving time was extended across the country to begin on the second Sunday in March rather than the first Sunday in April. But CEC’s findings were rather underwhelming. The DST extension cut California’s annual energy consumption by a mere 0.2%.
So why bother going through the twice-yearly ritual of being too early or too late for your meetings, just because you trusted the clock on your microwave too much? There might still be reasons. In the Nitty-Gritty, we’ll delve into reports that say Daylight Saving Time is still a good idea—it just needs to be structured differently. Smarter DST in California might save up to 3,400 MegaWatt hours a day in the winter months. And DST may play a critical role in making renewable energy grids feasible: renewables such as wind and solar are much more sensitive to annual and daily weather cycles and the timing of peak power demand. Whether or not the DST model we use now conserves energy, some form of seasonal time adjustment will probably become a crucial part of using more environmentally friendly energy sources.