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January 24, 2017 by Jeffrey J. Cook

Cities, or municipalities, account for over 70% of worldwide energy consumption. In the United States, city governments have authority over functions such as land-use, building development, transportation, and a variety of other policy areas that can impact energy use. Cities have used this authority to create incentives for the development of clean energy within their jurisdictions through planning, programming, and codification. Codification refers to the process whereby cities establish city ordinances, or laws. Codification can offer more certainty that policy goals will be achieved, given that repealing ordinances typically requires a vote by city government.

Though anecdotal or technology-specific evidence of municipal codification of clean energy priorities has been reported, the scope of this activity is unclear.[1] Moreover, it is also unclear how cities are referencing clean energy in their municipal code, whether this varies across the states, and what impact this codification has on achieving outcomes. A recent National Renewable Energy Laboratory (NREL) report titled: Clean Energy in City Codes: A Baseline Analysis of Municipal Codification across the United States begins to address all three gaps in the literature.

To estimate the scope of clean energy codification in the United States, the report builds a 20% representative sample of cities by state with populations over 2,500. This corresponds to 1,266 cities in total across all 50 states. The authors then searched municipal codes for references to certain clean energy keywords relating to energy generation (i.e. solar and wind) and sustainable transportation (i.e. electric vehicles and smart growth).[2]

Overall, 59% of cities referenced at least one clean energy keyword, suggesting that city governments are using codification as a tool to influence clean energy development in their jurisdictions. Eighty four percent of the references addressed energy generation with the three most common keywords being solar, wind energy, and geothermal.[3] Figure 1 illustrates the state and regional differences in energy generation keywords referenced across the states and the percentage of cities within each state that referenced keywords.

Figure 1. Breakdown of energy generation references by state and proportion of municipalities by state to reference at least one energy generation keyword


The report offers perspective on the baseline regarding how certain keywords are referenced by city governments. Focusing on solar, the report analyzes code references in the states of California, Florida, Maryland, and Minnesota. The distribution of references by policy category is outlined in Figure 2. Overall, nearly 75% of the references addressed development and design standards, solar access, or permitting.

Figure 2. Solar references by policy category

Solar references by policy category.

According to the study, development standards typically address solar installation requirements on buildings, solar access references stipulate building owner rights to sunlight, and permitting references relate to setting fees and clarifying review processes among others. One notable difference between the solar reference analysis and that for wind energy was the standardization identified in 49% of the wind energy references. These codes were roughly identical, where references were included in an all-encompassing wind energy code, which was not the case for solar or geothermal. The authors posit that this finding could illustrate wind technology or market maturity that could serve as a model for other technologies such as solar.

Finally, and unique to solar, the report conducts a comparison of cities across six states (Arizona, Georgia, Massachusetts, Minnesota, New York, and New Jersey) to assess the potential relationship between the presence of solar references in a city’s code and solar capacity. In each state analyzed, cities with references to solar had more solar installed per capita than those with no references (Figure 3).

Figure 3. Average installed solar PV Watts per capita for municipalities across select states by substantive solar reference


Ultimately, this work illustrates that cities are employing their code as a policy mechanism to address clean energy. To date, it is unclear whether favorable codes cause clean energy deployment or developer activity causes cities to adopt codes. From this perspective, the report concludes by outlining a research roadmap to examine the overall role of codification in shaping policy outcomes and achieving clean energy goals. The intent of the roadmap is to further clarify the specific relationships between municipal codification and clean energy, particularly as it relates to market development.

[1] For example, Smart Growth America tracks complete streets ordinances across the states, the American Planning Association provides a database of local solar-related policies and zoning codes, and the U.S. Department of Energy’s (DOE’s) WINDExchange tracks wind energy ordinances.

[2] The report also evaluates building energy codes, but in a separate analysis with a unique methodology.

[3] Solar accounted for 41% of all the references.

Tags: Policy