An urban scaling model for energy use in cities

Cities are complex systems that display scaling behavior. Furthermore, they are the human habitats where we can better understand issues of resource consumption and sustainability. In this research, we seek to explore how to... [ view full abstract ]

Cities are complex systems that display scaling behavior. Furthermore, they are the human habitats where we can better understand issues of resource consumption and sustainability. In this research, we seek to explore how to interpret the energy-related scaling relationships observed in cities. In doing so, we add to the body of knowledge about how to build more sustainable, resource-efficient cities and to the general understanding of urban metabolism across scales.

We first present an overview of what is known about energy scaling in cities, including a review of empirical results in the literature and theoretical frameworks for understanding scaling in cities. We then further unpack the theoretical concepts surrounding urban scaling using the paradigm of thermodynamics. Taking this approach, we define system states of cities, including growth and decline, in terms of energy consumption and reinvestment into physical infrastructure. Our theory is supported with new empirical results with energy-related data for cities in the United States. For example, fuel wasted as a result of congestion—an example of wasted energy—scales superlinearly with population (β = 1.33 ± 0.04 [95% Confidence Interval], R² = 0.90).

Our results have important implications for sustainability and cities. The world is urbanizing at a rapid rate, and the scaling relationships indicate that larger cities will consume even more energy per person than their smaller counterparts. Our model confirms that while infrastructure investment can promote efficiencies, it can also drive growth and increase overall energy consumption. In this sense, larger cities are more efficient in many ways, but they are not necessarily more energy efficient. This result points to the need for strategies that can sustain potentially high energy use while reducing adverse impacts, such as a shift to low-carbon energy supplies, particularly in rapidly urbanizing regions.