As California races to meet its mandate of 100% clean electricity by 2045, the state faces a significant hurdle: utility-scale solar deployment is currently averaging 1 to 3 GW per year — well short of the 4 to 7 GW necessary to meet the goal.
While a complex mix of interconnection, permitting, land use and workforce training are often cited as major bottlenecks, a first-of-its-kind study released by The Nature Conservancy (TNC) and ECOnorthwest provides hard data on what is actually driving these delays.
The report, titled “The Pace of Solar Progress,” contains an analysis of over 15 years of permitting data for 274 proposed utility-scale solar projects in California in various stages of the permitting process.
Through their work, the researchers came to a clear conclusion: where solar projects are built determines how fast solar projects are built, to a far greater extent than project-level factors like size and distance to communities.
Specifically, the authors found that solar projects sited on lands already shaped by human activity move through the county permitting process significantly faster than those proposed on undisturbed natural lands.
To quantify this effect, the researchers used the Human Modification Index (HMI), a metric that measures the extent to which a project site has been altered by human activity, ranging from 0.0 (low modification) to 1.0 (high modification).
The analysis found that, all other things being equal, a 0.1-point increase on the HMI scale increases a project’s chance of approval by 21%, the equivalent of shaving approximately 50 days off the permitting timeline.
The research further revealed a median duration for the approval of projects of 420.5 days, with a breakdown showing that the median was 110 days for projects on developed lands, 338 days for projects on agricultural lands and 621 days for projects in open space.
The corollary to these findings is that factors many developers assume contribute to slow permitting do not show meaningful impacts.
Notably, things like project size, distance to the nearest community and the year of initial permit application show limited effects on permitting timelines in the areas studied.
The researchers assert that the findings should act as a guide for developers and state policymakers, advising the former group to focus on building projects on already developed land and encouraging the latter group to enact reforms to align interconnection, permitting and project development processes.
The epicenter of California solar
The study focused on a region of eight counties in the San Joaquin Valley and portions of the West Mojave, an area that the researchers say contains 43.5% of the state’s existing solar capacity, and which may play host to an even greater share of development in the future.
Developers in this area must navigate the complex balance between preserving prime agricultural land, managing groundwater, and protecting sensitive ecological habitats.
Because changes in water availability and policies like the Sustainable Groundwater Management Act (SGMA) are forcing the retirement of intensive cropland, landowners have strong financial incentives to convert their farms into solar facilities.
However, not all agricultural land is treated equally in the permitting process. The report highlights that projects located on lands enrolled in Williamson Act contracts — which offer tax breaks to landowners who restrict their land to agricultural or open space use — face a 38% lower chance of approval, adding roughly 245 days to the permitting process.
The study found that developers already show a strong preference for modified lands, with 74% of the analyzed projects sited on agricultural lands, and only 21% located on open space.
But the researchers noted that the availability of “low-conflict lands” is declining, meaning state policymakers will need to act to balance the goals of land use, groundwater sustainability and conservation with the need for rapid clean energy expansion.
“California is a national and global leader in driving the urgently needed transition to a clean energy economy,” said Chuck Bonham, Executive Director of The Nature Conservancy in California in a statement. “This study demonstrates that we can accelerate that transition and protect nature simply by using readily available information early in the project development process. California can secure a clean energy future without trading off places that are important for the plants and animals that also call the Golden State home.”
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