Daylight Saving - Energy saving or energy wasting?
Here is an excellent discussion on slashdot about the effect of daylight saving time on overall energy consumption. Included is a link to Wall Street Journal article describing a study at UC Santa Barbara.
A recent legislation passed in Indiana, USA changed daylight saving time policy of the state and gave the reserchers unique opportunity to observe the effects on electricity bills before and after the change. The conclusion? “The study unambiguously concludes that Daylight Saving Time not only doesn’t save any energy, it actually wastes energy and costs more.”
Indeed at some point in time, especially around and after the world war - II, the practice of daylight saving time resulted in energy savings. People were able to use more of sunlight instead of the lights inside, and were able to save a money on electricity bills.
Then came air conditioning.
When an air conditioner or a heater runs for an extra hour because of time change, it far more than offsets the amount of energy saved by switching off the lights. As shown in one of my previous posts, air conditioner is the biggest energy hog. The proportion of energy consumed by air conditioner is far higher and thus makes the daylight saving theory questionable.
Delaying the nominal time of sunset and sunrise reduces the use of artificial light in the evening and increases it in the morning. As Franklin’s 1784 explanation pointed out, lighting costs are reduced if the evening reduction outweighs the morning increase, as in high-latitude summer when most people wake up well after sunrise. An early goal of DST was to reduce evening usage of incandescent lighting, formerly a primary use of electricity.[6] Although energy conservation remains an important goal,[24] studies are contradictory, and suggest that DST can increase energy use in some common cases:
The U.S. Dept. of Transportation (DOT) concluded in 1975 that DST might reduce the country’s electricity usage by 1% during March and April,[25] but the National Bureau of Standards (NBS) reviewed the DOT study in 1976 and found no significant energy savings.[21]
In 2000 when parts of Australia began DST in late winter, overall electricity consumption did not decrease, but the morning peak load and prices increased.[26]
Although a 2007 study estimated that introducing DST to Japan would reduce household lighting energy consumption,[27] a 2007 simulation estimated that DST would increase overall energy use in Osaka residences by 0.13%, with a 0.02% decrease due to less lighting more than outweighed by a 0.15% increase due to extra cooling; neither study examined non-residential energy use.[28]
DST may increase gasoline consumption: U.S. gasoline demand grew an extra 1% during the newly introduced DST in March 2007.[29]
A 2007 study found that the earlier start to DST that year had little or no effect on electricity consumption in California.[30]
A 2007 study estimated that winter daylight saving would prevent a 2% increase in average daily electricity consumption in Great Britain.[31]
A 2008 study examined electricity billing data in Indiana before and after it adopted DST in 2006, and concluded that DST increased electricity consumption by 1% to 4%, primarily due to extra afternoon cooling.[7
Excellent comment Mike. Thanks.
The theory of increased air conditioner time may work in the extreme southern U.S. However, wouldn’t the reverse be true in the northern part of the country. I live in Knoxville, TN (relatively south) and checked NOAA’s website for heating and cooling info. There were 0 Cooling Degree days for the week ending March 15th, and 114 Heating Degree days. Using the same logic you used in your article, wouldn’t less heating be required, wehter electric or gas?
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It’s interesting that the exact opposite of the original intention of the change is happening. Technology changes everything