, , , , , , , , , , , , , , , , , , , ,

(originally published to Helium writing site, now gone)

One of the major reasons countries have daylight saving time is its potential to save energy. The main savings come from household lighting, which only uses 3-4 per cent of electricity consumed in the United States and Canada. From this low base, the amount of fuel saved by having domestic lights on for an hour less each day in the evening for half the year is small. A proportion of this savings is rubbed out as people use more artificial light in the morning.

The first study of how the better utilization of daylight would save energy was by Benjamin Franklin in 1784. His letter to the editor of the Journal of Paris was published under the title “An economical project for diminishing the cost of light”. He estimated that Parisians used 128 million candle hours a year unnecessarily. This used about 29,000 tons of wax and tallow, which cost 96 million livres tournois (or more than $200 million in today’s money), “an immense sum! that the city of Paris might save every year, by the economy of using sunshine instead of candles”, Franklin exclaimed. But the savings were exaggerated as he assumed people used candles seven hours a night in summer months and got up at noon.

Over a century later, Englishman William Willett, who fought long and hard for the introduction of daylight saving, came up with a more rigorous analysis of the savings. In his booklet, “The Waste of Daylight”, which he published in 1907, he estimated the total energy savings his idea could be expected to generate for Great Britain and Ireland. He assumed the cost of artificial light was a tenth of a penny per head per hour. Under the scheme, the total amount of extra daylight in the evening was 210 hours a year. Using a population estimate of 43.66 million, gross savings equated to 3,820,250 pounds in a year. He then deducted a third of this “to meet all possible objections, including loss of profit to producers of artificial light”, arriving at net savings of 2,546,834 pounds.

Indeed the main reason daylight saving time was finally introduced, in 1916, was to save fuel for the war effort. Germany was the first country to start daylight saving time, with many other countries soon following, including the United Kingdom. When World War I finished in 1918, most countries stopped using it. They resumed it during World War II, again to save energy, some countries turning their clocks forward two hours in summer and leaving them one hour ahead in winter. Another rush to adopt daylight saving time took place during the energy crises of the mid 1970s to early 1980s. A number of countries have adopted daylight saving time when fuel costs have soared and stop using it when prices ease.

Studies over the years have indicated that daylight saving time doesn’t save a great amount of fuel. Like many countries, the United States had daylight saving time during World War II. However, in 1941, President Roosevelt could only claim that it saved about 700 million kilowatt hours of fuel for defense purposes. This equated to 0.5 per cent of power production or enough to run the 2.5 million refrigerators Americans bought in the first half of 1941.

A study by the US Department of Transport in 1975 estimated that daylight saving time lowers electricity use by 1 per cent in March and April. But the National Bureau of Standards reviewed the study and found negligible savings. More recent studies in the United States have shown similar findings. In 2007, an early start to daylight saving had little effect on California’s power usage. A three year study of electricity consumption in Indiana showed that usage was 1 per cent higher with daylight saving time, resulting in an extra $9 million added to household power costs. A US Department of Energy study found that the daylight saving time extension in 2007 only saved 0.5 per cent of fuel consumption.

Studies in other countries have given disappointing results too. In Australia in 2000, when daylight saving time started in late winter for the Sydney Olympic Games, electricity use increased in the mornings while overall consumption was unchanged. Western Australia is trialing daylight saving time for three years from 2006-07 to 2008-09, but found that electricity consumption rose 0.6 per cent in the first summer. In Japan, a study of residential energy use in Osaka estimated there would be virtually no difference in electricity consumption if daylight saving time was introduced. The slight saving in lighting was offset by a small increase in electricity for cooling as people got home earlier in the afternoon. Ironically, a study in the United Kingdom in 2007 found a 2 per cent saving in electricity usage if daylight saving time was used in winter!

Thus the ability of daylight saving time to save energy appears to be limited. Yet over the decades, apparent fuel savings have been the main reason most countries have adopted it. Most studies have found that a reduction in lighting in the evening is offset by greater usage in the morning and an increase in cooling.