A year ago, we covered the newly extended daylight-saving time (DST), which, as part of the Energy Policy Act of 2005, was expected to generate energy savings nationwide. But a recent Wall Street Journal article reported that the extra month of daylight time might actually be costing us money, not saving it as planned.

Matthew J. Kotchen and Laura E. Grant, economists at the University of California at Santa Barbara, conducted an energy-use study in southern Indiana, calling it a “natural experiment” because the entire Hoosier state adopted DST only in 2006. Until then, Indiana farmers, unenthusiastic about working in dark morning hours, had prevailed upon the state not to change its clocks.)

Comparing monthly energy bills over a period of three years, the study estimates that DST has cost Indiana households $8.6 million, an increase of up to 4 percent. Fortunately for residents of the Hoosier State, the extra money translates into only $3.19 per household.

In the Journal article, Representative Edward J. Markey, the Massachusetts Democrat who in 2005 helped draft legislation to extend daylight time, pointed out that a study in southern Indiana “cannot accurately asses the impact of [daylight-saving time] changes across the nation, especially when it does not include more northern, colder regions." In their study, Kotchen and Grant acknowledge the need for more extensive research.

The premise behind extending daylight time grew out of a 1975 study by the U.S. Department of Transportation that suggested longer daylight hours would save energy and money. But while the study found an overall reduction in electricity used for lighting, increased heating and cooling demands offset those savings. The result: a net increase of energy costs.

When the DST extension was being debated in 2005, several groups opposed the extension, citing increased inconvenience and concerns about children and auto accidents on dark mornings. Proponents of the extension have pointed to a 1995 study that found that there were fewer fatal traffic accidents overall during daylight-saving time because most accidents occur in the evening. The National Highway Safety Traffic Administration is still compiling traffic-accident data for 2007, the first year during which extended DST was in effect.

While it’s too early to know if Kotchen and Grant’s findings extend to all U.S. households, the arrival of DST is a good time to check batteries in smoke and carbon-monoxide alarms, program your thermostat for maximum energy conservation, and tackle these other household chores.