Visualizing solar capacity, performance across the US

Solar capacity factors rose across all independent system operators in 2020, pushing the weighted U.S. average up 1.8 percentage points year over year as more than three-quarters of the states housing utility-scale solar projects experienced increases.

The 2020 weighted U.S. solar capacity factor comes in at a calculated 24.4%, based on S&P Global Commodity Insights estimates. The California ISO tops the ISO leaderboard at nearly 27%, but Utah leads the pack across state lines, with solar plants in the Beehive State averaging almost 30%. Wisconsin, meanwhile, logged the largest gains from 2019 to 2020, up an estimated 8.6 percentage points.

With California accounting for most of the CAISO footprint, the ISO's calculated capacitor factor reflects that of the Golden State. Multitudinous solar plants pepper California, contributing to CAISO's undisputed ISO solar capacity leadership, with more than 12 GW across developments included in this analysis. Furthermore, scale and associated running times help keep the footprint at the forefront of solar capacity factors.

California boasts four of the nation's top five solar plants by operating capacity, with capacity factors ranging from 24% to 30% in 2020. The group of four includes U.S. solar capacity leader Topaz Solar Farm, owned by Berkshire Hathaway Energy subsidiary BHE Solar LLC in San Luis Obispo County, home of California Polytechnic State University. Pacific Gas and Electric Co. contracts 100% of Topaz's 586 MW. The group also includes BHE Solar LLC's 310-MW Solar Star (Antelope Valley Solar Project I) at the western tip of the Mojave Desert, less than 80 miles north of Los Angeles. Combined with Solar Star (Antelope Valley Solar Project II), Solar Star is one of the largest in the U.S. Southern California Edison Co. has a 20-year power purchase agreement with the project.

Utah topped the state solar capacity factor charts in 2020, but the state ranked eighth in operating solar capacity, with only 917 MW, or less than 8% of California's total, according to Commodity Insights data. Smaller projects make up the bulk of Utah's solar portfolio, with 58% of the state's utility-scale solar plants showing an operating capacity under 5 MW based on 2020 data.

Sunny southwestern Utah, adjacent to Arizona and Nevada, however, counted several 80-MW solar developments, including Goldman Sachs Renewable Power LLC's Utah Red Hills Renewable Park and Clearway Energy Inc.'s Escalante Solar II Plant (Four Brothers) and Enterprise Solar Plant (Four Brothers). All three plants had capacity factors over 30% in 2020.

Notably, Utah's Desert Southwest neighbors Arizona, Nevada and New Mexico round up the top four solar capacity factor states. All four markets are regulated. Green energy-hungry corporations, an increasingly significant driver of renewable energy deployment, often prefer direct access to generators, favoring unregulated markets. Commodity Insights research shows that in the U.S., more than 60% of identified corporate-tied renewable capacity has been contracted in deregulated states.

That said, Utah has a voluntary renewable portfolio standard for utilities to procure 20% of retail sales via renewable sources by 2025. In Arizona, the Arizona Corporation Commission in 2006 approved the Renewable Energy Standard and Tariff, which requires regulated electric utilities in the state to generate 15% of their energy from renewables by 2025. Both New Mexico and Nevada have renewable portfolio standards. New Mexico's renewable portfolio standard requires 80% renewables by 2040 and 100% zero-carbon electricity by 2045. In Nevada, the renewable portfolio standard aims at 50% renewable energy by 2030, with interim targets in the interval.

Arizona, Nevada, New Mexico and Utah have a combined 24.7 GW in planned solar capacity, according to S&P Global Commodity Insights data.

^{Regulatory Research Associates is a group within S&P Global Commodity Insights.}

^{S&P Global Commodity Insights produces content for distribution on S&P Capital IQ Pro.}

^{Chris Allen Villanueva, Kristin Larson and Monesa Carpon contributed to this article.}

^{This article was published by S&P Global Market Intelligence and not by S&P Global Ratings, which is a separately managed division of S&P Global.}