[jseliger]

Someone living in New York has half the energy footprint of the average American

This is absolutely true and some of the daughter comments are missing the point; see Edward Glaeser's The Triumph of the City (http://www.amazon.com/Triumph-City-Greatest-Invention-Health...) for more details, but people in urban environments tend to drive less and drive shorter distances; they're less likely to own cars in general and more likely to take mass transportation or bike; and their overall energy usage for heating and cooling is much lower because they share those costs (and walls) with neighbors.

Everyone has to live somewhere, and every time a five to fifty story building gets blocked in a city, dozens or hundreds of high-energy-cost, detached single-family houses get built in Phoenix, Houston, Dallas, and Atlanta.