Whoops! Maybe Daylight Savings Time Wastes Energy!

The conventional wisdom on daylight savings time has always been that it's a way to save energy by cutting down on the amount of lighting used at night.

Like a lot of conventional wisdom, it may turn out that's not true.

A new study out of Indiana concludes that while daylight savings time reduced lighting costs, it increased air conditioning costs in the evenings during summer, and may have increased heating costs in the mornings in winter, producing a net INCREASE in energy use overall. (See "Daylight Saving Wastes Energy, Study Says" in today's Wall Street Journal.)

It's a pretty good study, but like all studies has its limitations. Researchers looked at the energy use patterns, taken straight from seven million monthly meter readings over a three year period, in 13 Indiana counties that finally switched to daylight savings time after years of opting out.

The study found that electricity use increased by 1%-4% as a result of the changeover, costing Indiana residents an additional $8.6 million a year in power costs.

The study is certainly plausible. Most of the earlier studies, upon which the conventional wisdom rests, were conducted in the 1970's, when daylight savings time was being introduced, but when air conditioning was far less ubiquitous than today (and when temperatures were slightly lower).

There are significant limitations on the research, however, particularly that rural Indiana may not be representative of the experience in other parts of the country. The study also did not examine other costs and benefits of daylight savings time, such as the increased recreational opportunities in the Spring and Fall from having an extra hour of evening daylight.

The issue certainly merits additional study--we ought to know the answer to whether daylight savings time is an energy saver or an energy waster.

That said, we wouldn't want to see the end of daylight savings time: we very much value that extra hour of daylight, especially in March and April, and in October, when we're trying to get a little more soccer playing time in for the kids.