Study: Solar Permitting Goes Faster on Already-Altered Land, Slower on Williamson Act Sites

How Land-Use History Shapes Solar Permitting Timelines

A first-of-its-kind analysis of over 15 years of permitting data from eight San Joaquin Valley counties reveals that the single biggest factor in how quickly utility-scale solar projects gain approval is not their size or distance from communities—it is the land they sit on. The Nature Conservancy and ECOnorthwest found that projects sited on already-altered land, such as fallow fields, industrial zones or land previously disturbed by human activity, consistently move through the permitting pipeline noticeably faster than those proposed on undisturbed natural lands.

The study, titled “The Pace of Solar Progress: How Preexisting Land Use Shapes Solar Permitting Timelines in California,” shows that the ecological sensitivity of pristine sites triggers longer reviews and more procedural hurdles. In contrast, degraded or previously modified lands present fewer environmental conflicts, reducing the complexity and duration of the permitting process. Notably, the research found that project size—often assumed to be a key driver of timelines—had no meaningful effect on how long it took to get approval.

Where land is protected under the Williamson Act, a California law designed to preserve agricultural and open space, the picture becomes more complicated. Projects on these lands require counties to make extra compatibility findings and sometimes navigate contract-cancellation rules, which adds significant time and uncertainty. The study concludes that this extra layer is slowing the buildout of solar capacity precisely on the kind of land that could soon be retiring from irrigated farming due to groundwater limits under the Sustainable Groundwater Management Act (SGMA).

What the Findings Mean for California’s Clean Energy Buildout

Why the Williamson Act is Creating a Bottleneck

The Williamson Act was never intended to be a barrier to clean energy, but the study’s data makes clear that it is acting as one. A county that wants to approve a solar project on enrolled land must first determine that the use is compatible with the act’s preservation goals—a determination that often draws opposition, requires extra hearings, and can be challenged. When combined with the laborious process of canceling a Williamson Act contract, the timeline stretches well beyond what is typical for similar projects on non-enrolled farmland.

This friction comes at a critical juncture. As SGMA forces the retirement of hundreds of thousands of acres of irrigated cropland in the San Joaquin Valley, much of that land is enrolled in the Williamson Act. Without a clear, voluntary pathway to transition from forced fallowing to solar generation, the state loses a prime opportunity to meet its climate targets while also giving landowners and counties a viable economic alternative.

The Degraded Land Advantage: A Predictable Permit Path

The study confirmed what many developers already suspected: siting on land that has little ecological value dramatically speeds up permitting. The data shows that only 21% of permit applications were for undisturbed natural lands, meaning developers are actively avoiding those sites because they understand the risks. This self-selection indicates that the market is ready to concentrate solar development on degraded lands if policy aligns. The missing piece, the authors argue, is a proactive state framework that removes remaining barriers—above all, ensuring that transmission capacity is directed to those same preferred sites.

What the Data Tells Developers and Policymakers

Because project size, community proximity and application year did not correlate with longer timelines, the study strips away several common excuses for permitting delays. The levers that actually matter are all tied to land-use policy. For developers, the take‑away is to double down on degraded land sites, not only to save time but to reduce regulatory risk. For the state, the report is a clear signal that aligning the Williamson Act with SGMA-driven land retirement and creating expedited permitting corridors for previously altered land could significantly shrink the timeline from application to construction.

Policies to Unlock Faster, Smarter Solar Deployment

• Align Williamson Act rules with groundwater realities. California should establish a voluntary, expedited process that allows landowners retiring irrigated land under SGMA to convert it to solar without enduring years of cancellation hearings. This directly addresses the specific bottleneck the study identified.
• Direct state incentives toward altered lands. Since the data proves these sites face far fewer ecological hurdles, policymakers should target grants, expedited review pathways and transmission planning specifically at degraded and previously disturbed land. This reinforces the market trend the study documented.
• Coordinate transmission planning with land use. Developers are already choosing altered land when they can, but a lack of transmission access on those sites is a deal‑breaker. The state should prioritize grid upgrades along the I-5 and Highway 99 corridors where much of this land sits to remove the last major obstacle.
• For developers, site early on altered land. The study confirms that projects on undisturbed natural land face unpredictable permitting. Development pipelines should be biased toward previously modified sites, with Williamson Act parcels treated as a second‑tier option unless SGMA retirement offers a clear conversion window.