A new analysis quantifies how setback ordinances are affecting wind and solar energy development.

The National Renewable Energy Laboratory said these local laws are multiplying but their broad effects typically have not been measured in large-scale assessments because of the extensive amount of data that is needed and the detailed modeling that must be built from it.

As a result, NREL said, previous assessments likely have overestimated the amount of land available for renewable development and underestimated the cost and difficulty of development.

If the most restrictive setback rules were imposed nationwide, the potential for wind development would drop almost 90% and solar nearly 40%, compared with a scenario in which no restrictions were in place.

It’s important to include these setbacks in resource assessments, the authors say, to accurately estimate the actual potential.

The NREL study — “Impact of Siting Ordinances on Land Availability for Wind and Solar Development” — was published Thursday in Nature Energy.

Reviewing state and local zoning laws and ordinances, the authors found 1,853 local wind rules in effect in 2022, compared with 286 four years earlier. They also found 839 local ordinances affecting utility-scale solar construction in 2022; no comparable data tally was made in previous years.

The most common types of regulations are minimum setbacks from roads, property lines and structures; noise level restrictions; and wind turbine height limits.

Setback distances typically are greater for wind turbines than solar arrays and often are calculated with some multiple of the turbine’s height.

Looking nationwide at land suitable for energy development — with no legal protections, wetlands, high elevations or other major limits — the study found the potential for construction of 147 TW of solar capacity and 14 TW of wind capacity if no setback restrictions were imposed.

This falls to 121 TW and 4 TW under the median distance among setbacks imposed nationwide and falls to 91 TW and 2 TW under the most restrictive setback rules — a decrease of as much as 38% for solar and 87% for wind.

“The increase in local zoning ordinances is a sign that the renewable energy industry is maturing,” lead author Anthony Lopez said in a news release. “Ordinances can provide a structured approach to thoughtfully weave clean energy infrastructure into society and our natural environments.”

A key takeaway, he said, is the importance of understanding the impact of renewable development on communities, and of providing communities with information to help them balance regulation of those impacts with the benefits of constructing renewable resources.

Other findings and caveats in the report include:

• • The impact of setback restrictions varies greatly depending on the nature of the community; Albany County, Wyo., and Erie County, Pa., have similar setback requirements for wind turbines, but Erie County is so much more densely developed that nearly the entire county is excluded from wind power installation.
  • Factors not examined in the report — such as environmental, ecological and security considerations — also influence land availability.
  • The report incorporates only zoning ordinances that had been posted online.
  • Energy developers sometimes can obtain exemptions from setback standards.
  • A few counties’ information is missing, so data was simulated for them.
  • There was no attempt to factor in local circumstances — such as when owners of two adjacent parcels agree to host wind turbines, and the setback requirements are canceled along the property line between them.

Setback data were combined with wind and solar data to model the renewable energy potential of a given area and the local ordinances’ impact on it.