Wasting energy by saving time?
“Spring forward, fall back”: For decades, that mantra has reminded bleary-eyed Americans each spring to prepare to lose an hour of sleep. But many did it willingly, because conventional wisdom held that Daylight Saving Time (DST) — during which clocks are set ahead an hour to better match actual hours of daylight in summer — ultimately reduces energy costs. A new study of energy use during DST, however, now suggests the opposite: that the adjustment may instead be costing Americans money. And lawmakers are taking note.
It was Benjamin Franklin who first proposed the economic basis for adjusting clocks to better match daylight hours — it would save quite a bit of candle wax, he noted. Some 130 years later, the idea was rekindled during World Wars I and II to save coal for the war effort rather than using it for electric lights. After World War II, some states and counties continued to implement DST, while others didn’t (which created some confusion).
The idea didn’t become permanent federal law until 1966, when the Uniform Time Act established late April to late October as the period of energy conservation (although it is a federal law, an entire state can choose whether or not to participate). Since then, DST has been extended several times — most recently in 2005, when the Energy Policy Act pushed the start date back to mid-March and the end date to early November (beginning in 2007). The adjustment, Congress estimated, would save hundreds of thousands of barrels of oil per day. That estimate was partially based on calculations from a 1975 study by the Department of Transportation (DOT) found that DST was saving energy.
But DOT’s results were later called into question. And since then, few rigorous studies have been done to determine whether DST does, in fact, save energy, says Matthew Kotchen, an environmental economist at the University of California at Santa Barbara. That’s true in part because estimating the impact of DST on electricity demand requires being able to make direct, simultaneous comparisons of energy usage in households that are on and off DST, and that are in the same geographic location — not an easy study to do, he says.
Such an unusual opportunity arose in 2006, when the state of Indiana — one of three long-time holdouts against DST, along with Arizona and Hawaii — began practicing DST statewide. DST had been a contentious issue for decades in Indiana, which has suffered something of a time identity crisis, as it also sits on the border between the Eastern and Central Time Zones. As a result, some counties were on Eastern time, some on Central, some observed DST and others didn’t.
Kotchen and postdoctoral student Laura Grant took advantage of the natural experiment under way in Indiana to study DST’s impact and compare energy use and savings between households. Compiling more than 7 million monthly bills from counties across southern Indiana — some DST-compliant before 2006, others not — they compared the energy use in two ways: first, between DST and non-DST homes before 2006; and second, between the same homes before and after Indiana uniformly adopted DST in 2006.
What they found, Kotchen says, is that “the ‘Ben Franklin’ effect is still there — [DST] saves on lighting.” But there’s a tradeoff: DST also increased the demand for heating and cooling. “In early spring and late fall, DST makes people wake up during the coldest, darkest part of the day, and so they’ll run the heat longer,” he adds. “At the same time, in the middle of summer when the days are hottest,” it stays light later. So, for example, “people might turn up the air conditioning when having dinner.”
Overall, the increase in residential electricity demand for climate control was greater than the decrease in demand for lighting, the researchers reported at a National Bureau of Economic Research meeting in February. Residential electricity demand increased by 1 to 4 percent, ultimately costing Indiana households $8.6 million more per year. Another factor, they noted, is the “social cost” of DST, in terms of paying for damages from increased pollution emissions. Increases in those emissions cost households between $1.6 million and $5.3 million per year.
The Department of Energy (DOE) is currently conducting its own study of the effect of the 2005 extension of DST on energy use. Although Congress passed the 2005 law, it also required that DOE study the extension’s impact, and retained the right to repeal the extension pending the results. The study, begun in late 2007 after DOE finished compiling data on hourly electricity use from utility companies, will be completed at the end of June, according to DOE spokesperson Chris Kielich.
Although such an extensive, large-scale study of DST’s impact is needed, “you can immediately see how problematic it is, because [the DOE study doesn’t] have a control group,” Kotchen says. However, extrapolating his own Indiana results to elsewhere in the country could also be problematic, he says. Air conditioning and heating costs can vary greatly across the country, as can lighting costs, and much of that also depends on the source of fuel.
“The major thing this raises is that we shouldn’t just myopically consider this an energy-saving policy,” Kotchen says. There are, after all, some worthwhile advantages to more waking time in the daylight. It can facilitate economic growth, cut down on traffic accidents and provide more time for outdoor activities.
That the law may be revisited or repealed might be heartening news to those who are tired of grumpily setting the clock ahead each spring. But meanwhile, “What time is it?” continues to be a highly charged question in Indiana, sandwiched between the competing interests of farmers, businesses and people living at the extreme edges of the time zones.