Sustainability Much Better In Warm, Rather Than Cold Cities
March 28, 2013

Sustainability Much Better In Warm, Rather Than Cold Cities

Brett Smith for - Your Universe Online

US citizens live, work and play in a variety of temperatures from coast to coast and living in the more extreme climate regions of the country means demanding more power in terms of heating or air conditioning.

As Americans strive to live more sustainably and efficiently — Michael Sivak, from University of Michigan´s Transportation Research Institute (UMTRI), has published a new report in the journal Environmental Research Letters that showed colder cities demand more energy than warmer cities.

"It has been taken for a fact that living in the warm regions of the US is less sustainable than living in the cold regions, based partly on the perceived energy needs for climate control; however, the present findings suggest a re-examination of the relative sustainability of living in warm versus cold climates,” Sivak said.

Sivak reached his conclusion by calculating that Minneapolis, “the coldest large metropolitan area” in the country, demands about three-and-a-half times more energy than Miami, “the warmest large metropolitan area in the US.”

The scientist calculated the two cities´ energy demand using three parameters: the number of heating or cooling degree days in each city, the energy use of heating and cooling appliances, and the capacity of area power plants.

To compare the two cities, Sivak used heating degree days (HDDs) and cooling degree days (CDDs) as climatological measures. The measures, which reflect the energy needed to heat or cool a building, are calculated by comparing the average daily outdoor temperature with 18 degrees Celsius. For example, a day with an average daily temperature of 10 degrees would have 8 HDDs and no CDDs, as the temperature is 8 degrees below 18. Conversely, a day with an average daily temperature of 23 degrees Celsius would have 5 CDDs and no HDDs.

Previous data showed Sivak that Minneapolis had 4376 HDDs a year compared to 2423 CDDs in Miami.

To determine how HDDs and CDDs translate into energy consumption, Sivak used a single metric for comparing the efficiency of heating and air conditioning appliances. He found that a typical air conditioner is about four times more energy efficient than a typical furnace.

"In simple terms, it takes less energy to cool a room down by one degree than it does to heat it up by one degree," Sivak said.

Sivak also determined that the energy used for heating was produced slightly more efficiently than the energy generally produced for cooling. This is due in part to the fact that cooling is primarily powered by electricity, while heating is generated from a variety of power sources, including oil and gas.

Based on his climate and efficiency metrics, Sivak showed that Minneapolis consumes substantially more energy than Miami.

"In the US, the energy consumption for air conditioning is of general concern but the required energy to heat is often taken for granted. Focus should also be turned to the opposite end of the scale — living in cold climates such as in Minneapolis, Milwaukee, Rochester, Buffalo and Chicago is more energy demanding, and therefore less sustainable from this point of view, than living in warm climates such as in Miami, Phoenix, Tampa, Orlando and Las Vegas," Sivak concluded.

In his report, Sivak noted that people generally tolerate heat better than cold; therefore, Miami´s advantage in energy consumption over Minneapolis might be slightly underestimated by his calculations.