DST! What is it good for?
Casual readers, beware! Another moderately long analytical post follows...
The Energy Policy Act of 2005 (link), which modified Daylight Savings Time (DST) in the US (to which Canada followed suit) in section 110, required the Secretary to file a report with Congress within 9 months after the effective date of the act. If the anticipated energy savings did not emerge, the Act provided Congress with a "Right To Revert" - that is, to change things back to the way they were. I was curious to know what the results of the change actually were.
A 2001 study in California concluded that energy savings from extending DST would only be one fifth to one half of one percent of daily demand, and a 2008 study in Indiana suggested that DST actually increases electricity demand. (See link.)
After much scouring of the Internet, I finally found a report (link), which appears to be the legally mandated report, dated October 2008. (This was late, by the way - if the act took effect in March 2007, the report should have been filed in December of that year.) The key findings? Electricity savings resulting from extending DST were estimated at less than 0.5% per day, or a total savings of 0.03% of total electricity consumption over the year. Total "primary energy consumption" savings over the year were 0.02%, and gasoline consumption and traffic volume changes were "statistically insignificant". California, however, estimated the savings were only 0.2% per day, but with error bars so big that there may have actually been a 1.4% *increase* in energy consumption.
For the figures they give in the Report To Congress(again, link) in Table 2-2, the average morning increase is 1.4% +/- 0.9%, and the average afternoon decrease is 2.5% +/- 1.2%. So both numbers have error bars that call the results into question - the daily average savings could be as much as 3.2% or it could be a net *increase* of energy consumption of 1%.
So why are we doing this DST thing again?
The Energy Policy Act of 2005 (link), which modified Daylight Savings Time (DST) in the US (to which Canada followed suit) in section 110, required the Secretary to file a report with Congress within 9 months after the effective date of the act. If the anticipated energy savings did not emerge, the Act provided Congress with a "Right To Revert" - that is, to change things back to the way they were. I was curious to know what the results of the change actually were.
A 2001 study in California concluded that energy savings from extending DST would only be one fifth to one half of one percent of daily demand, and a 2008 study in Indiana suggested that DST actually increases electricity demand. (See link.)
After much scouring of the Internet, I finally found a report (link), which appears to be the legally mandated report, dated October 2008. (This was late, by the way - if the act took effect in March 2007, the report should have been filed in December of that year.) The key findings? Electricity savings resulting from extending DST were estimated at less than 0.5% per day, or a total savings of 0.03% of total electricity consumption over the year. Total "primary energy consumption" savings over the year were 0.02%, and gasoline consumption and traffic volume changes were "statistically insignificant". California, however, estimated the savings were only 0.2% per day, but with error bars so big that there may have actually been a 1.4% *increase* in energy consumption.
For the figures they give in the Report To Congress(again, link) in Table 2-2, the average morning increase is 1.4% +/- 0.9%, and the average afternoon decrease is 2.5% +/- 1.2%. So both numbers have error bars that call the results into question - the daily average savings could be as much as 3.2% or it could be a net *increase* of energy consumption of 1%.
So why are we doing this DST thing again?