Most of us live and work in cities, even when those cities don’t always correspond to the popular image of tall buildings and rushing crowds.

As the world urbanizes at an historic pace, countries that began the industrialization cycle more than a century ago are struggling to match creaking and multi-layered infrastructures with growing and shifting requirements for plentiful and affordable electricity.

A number of US cities have taken the lead on energy efficiency efforts and energy policy development, often in the absence of a federal US policy on energy or traded carbon markets that would provide a price signal to consumers without local requirements.

Traditional urban cores are often naturally energy efficient as more and more people are packed into tight spaces, and buildings can eke out the maximum impact for their energy input on a per-person basis. But not all cities are efficient, and not all of them are green in their energy consumption. Little is more shocking for the residents of aging US historic urban centers than the huge and half-empty climate controlled and brightly lit spaces of many fast-growing sprawl cities, where energy waste is often as flagrant as it is ignored.

But leadership in energy efficiency gains and in engaging with the problems presented by strained electricity infrastructure is not limited to one kind of city or one region of the country; cities have taken approaches as diverse as their skylines.

Cities are confounding in their variety, and this week Breaking Energy will highlight their leadership while acknowledging their differences in a short series of dedicated posts on cities and energy in the twenty-first century.

Look for Breaking Energy’s cities special coverage this week under the tag “Urban” and tell us what your city has, or hasn’t, done to engage with the challenges of the new energy economy.