Running Hot and Cold

People in Miami can now feel slightly less guilty for using air-conditioning in the summer. According to a new study, cooling down hot cities in the US is far less energy-intensive than warming up cold cities.

There’s no question that AC eats up a lot of energy. But “the energy demand from living in a cold climate such as the Midwest or Northeast is frequently taken for granted,” writes the study author, Michael Sivak at the University of Michigan Transportation Research Institute in Ann Arbor, Michigan.

Sivak decided to compare Miami, the hottest major US city, to Minneapolis, the coldest. First, he calculated how often and by how much the cities’ temperatures strayed from 18 degrees Celsius. He also accounted for the efficiency of furnaces, boilers, air conditioners, and power plants.

The amount of annual heating that Minneapolis requires is higher than the annual cooling that Miami requires, Sivak reports in Environmental Research Letters. And that heating takes more energy than cooling, since furnaces and boilers are only about a quarter as efficient as central air conditioners.

Overall, Minneapolis’ energy requirements for climate control are 3.5 times higher than Miami’s, Sivak estimates. He speculates that since people “are generally more tolerant of heat than of cold,” Miami’s energy usage might be even lower than his study suggests. Roberta Kwok | 29 March 2013

Source: Sivak, M. 2013. Air conditioning versus heating: climate control is more energy demanding in Minneapolis than in Miami. Environmental Research Letters doi: 10.1088/1748-9326/8/1/014050.

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