DST FACTS DST FACTS For most people, daylight-saving time means switching clocks ahead by one hour Saturday night and getting to church, work, or other activities on time Sunday.

and getting to church, work, or other activities on time Sunday. The official start of daylight saving time is at 2 a.m. Sunday. Many people will reset their clocks before going to bed Saturday.

A few parts of the country do not observe daylight time. Those include Arizona, Hawaii, Puerto Rico, the Virgin Islands, American Samoa, Guam and the Northern Marianas.

Standard time returns Nov. 2. Source: Associated Press WASHINGTON  For Benjamin Franklin, daylight saving time was about saving candles and for modern lawmakers, it's about electricity — but a recent university study found it might actually cost more energy when the nation resets its clocks Sunday. Matthew J. Kotchen, a professor of environmental economics at the University of California in Santa Barbara, and Laura E. Grant, a doctoral student in the same field, studied the effects of daylight saving in Indiana, where some counties used it and others did not. The states changed the law two years ago so that all counties now use daylight saving time. In an interview, Kotchen said using residential electricity bills for Indiana, he and Grant found that daylight saving time reduced electricity use for lighting but that more was used for air conditioning in the summer and heating in the fall than was saved. Question: Why was the study done? Answer: Conventional wisdom and the rationale for daylight saving time has been as an energy saving policy. The point of the study was to actually evaluate whether it does in fact save energy because there has been surprisingly little research that has looked into that question. What were the results? We found based on the natural experiment in Indiana that contrary to the conventional wisdom, daylight saving time ... decreases consumption for artificial illumination but increases consumption for heating and cooling. The magnitude of our estimate (for increased usage) ranged between 1% and 4%. In the study, what was the cost of daylight saving time? The change in costs to Indiana residents in terms of increased electricity demand ... is just over $3 per household per year. Over the whole population, that comes out to $8.6 million a year. Another element ... is the social (and economic) cost of pollution emissions. Having to generate more energy for electricity means there is going to be more pollution. We estimate those costs are between $1.6 million and $5.3 million per year in increased pollution costs. Do the results apply to the whole nation? Based on places that have similar sunrise and sunset times and climate of Indiana, the same results might apply. But while this is the effect in Indiana, and we suspect that it is in a lot of other places ... there may be places where daylight saving time actually does save energy. We're currently working on further research to try to come up with estimates for the nation as a whole. How was the study conducted? For several decades, only some counties in Indiana had practiced daylight saving time and a majority had not. Then in 2006, they all turned it on. We got residential electricity billing statements for over 250,000 households, some in the counties that experienced the policy for the first time and some in the counties that didn't have a change in policy. In the end, we simply compared the difference between before and after between the two groups, which enabled us to isolate the effect of daylight saving time. What does the study mean for using daylight saving time? The immediate thing ... is whether or not we should be continuing to use the energy argument as the reason for why we do daylight saving time. There are other reasons we might want daylight saving time ... like increased leisure activities. Some people argue it is better for health and it actually stimulates economic growth. Those are other things that we should want to account for and be part of the discussion. If we decide that energy is what we care about, we may want to ask what is the best time for having daylight saving time. Maybe the dates we have are not optimal for reducing energy consumption. Conversation guidelines: USA TODAY welcomes your thoughts, stories and information related to this article. Please stay on topic and be respectful of others. Keep the conversation appropriate for interested readers across the map.