After a Long Pause, California Electricity Sector Emissions Are Down. What Happened?

Over the last few years, California has witnessed a notable decline in heat-trapping emissions originating from its electricity sector.

Are you surprised by this news? Probably not! California has consistently taken the lead in the deployment of clean energy, setting remarkable records almost annually. This should logically mean that California’s emissions have been continually decreasing… right?

Unfortunately, that’s not entirely true. I’ve been monitoring this issue closely, and it’s disheartening to note that before the recent years, California’s electricity sector emissions had remained stagnant for approximately five years.

As the State progresses toward its clean energy and climate objectives, it’s critical to periodically reassess our progress. I aimed to investigate the reasons behind the stagnation of emissions from California’s electricity sector from 2017 to 2022 and the factors contributing to the recent decline.

I will explore these questions and more in this article.

Emissions Fluctuations

First, it’s vital to highlight the significant advancements California has made in reducing electricity sector emissions over the last twenty years. The state has halved these emissions since peaking in 2001, but the journey has been far from straightforward.

A severe drought between 2007 and 2009 caused a drastic reduction in hydroelectric power generation, leading to a surge in emissions as fossil fuel generation compensated for the shortfall. Likewise, in 2012, emissions spiked again following the abrupt shutdown of the San Onofre Nuclear Generating Station, which also necessitated increased reliance on fossil fuels.

While California’s emissions trajectory in the electricity sector has always exhibited fluctuations, it is particularly puzzling why emissions flatlined after 2017. Let’s take a close look at the past decade.

Growth of Renewable Energy

The first area of inquiry is the trends surrounding California’s clean electricity generation. Remarkably, the state has made substantial progress in expanding the share of renewable energy in its grid over the past ten years.

Unsurprisingly, solar energy has emerged as the centerpiece of California’s clean energy transition, with solar generation soaring almost fivefold since 2014. Wind power—which started with a higher initial generation level—has still seen an increase of nearly 40% in the same timeframe. Meanwhile, nuclear, geothermal, and biomass generation levels have largely remained consistent over the past decade.

Hydropower, represented in blue on the graph, shows notable variability. After plummeting due to a multi-year drought, hydro generation peaked in 2017 during a wet year that prompted record precipitation (and coinciding with the Oroville Dam crisis!). However, year-to-year fluctuations in precipitation have caused hydropower output to vary significantly, making it a crucial factor in understanding these emissions dynamics.

The Stability of Emissions Generation

Examining clean electricity generation presents only half the story. Equally important is analyzing the emitting generation—particularly from natural gas and unspecified imports—which considerably contributes to California’s greenhouse gas emissions. A detailed breakdown reveals why California’s electricity sector emissions remained stagnant.

In essence, both clean and emitting generation effectively remained constant from 2017-2022.

On the clean side, when combined, all sources of renewable generation resulted in a relatively flat trend. This is attributed to the earlier higher hydropower generation that later decreased, counterbalancing the increase in solar power.

On the emitting end, a substantial portion—around three-quarters—of emissions stem from natural gas. Although there have been slight increases in gas output recently, these gains were offset by a significant reduction in unspecified imports. Coal generation, while continuing its consistent decline, remains a minimal component of California’s energy mix, thus exerting little influence on overall emissions trends. Consequently, total emissions from emitting resources remained relatively steady from 2017 to 2022.

Additionally, it’s essential to note that despite discussions about rapid load growth from data centers, manufacturing, and electric vehicles, the energy demand across most of California’s grid has remained stable over the last decade. (This stability has been partially supported by the expansion of rooftop solar which has mitigated small increases in demand.) While current load growth doesn’t seem to have played a significant role in affecting emissions trends, future increases could shift the narrative concerning emissions if not managed properly. To mitigate potential impacts, it’s crucial to integrate electric vehicles and data center operations into the grid sustainably, thereby lowering emissions and supporting grid reliability.

Thus, with stable emissions generation contributing to emissions remaining steady, we can now address the promising developments.

Recent Decline in Emissions

As I highlighted earlier, California’s electricity sector emissions have resumed a downward trajectory in the past couple of years. The state-wide emissions data utilized in the first graph was sourced from the California Air Resources Board (CARB), which, as of my last check, has yet to release data for 2023 and 2024. However, we can reference data from the California Independent System Operator (CAISO).

CAISO covers approximately 80% of California, making its emissions data closely aligned with state-wide trends. After a protracted period of stagnation, CAISO’s emissions have witnessed a marked decrease in 2023 and 2024. Early indications suggest that emissions will be stable at least in 2025, as evidenced by the emissions in the first half of each year (illustrated in a dotted line). This indicates that clean generation is once again displacing fossil-fuel-generated power.

Aiming for Clean Electricity Goals

Looking forward, California has set ambitious objectives for clean energy, but significant work remains to achieve these goals. The California Public Utilities Commission (CPUC) plays a pivotal role in determining the electricity sector’s aims through its Integrated Resource Planning (IRP) process, with the latest decision setting emissions targets for specified years.

The immediate target is to lower state-wide electricity sector emissions to 30 million metric tons (MMT) by 2030. This goal is attainable, but achieving it will require utilities to sustain the pace of reductions witnessed in recent years. This entails ongoing rapid development of solar, wind, and energy storage solutions, alongside minimizing dependence on hydropower due to its historical volatility and susceptibility to increasing climate extremes.

Regrettably, California’s investor-owned utilities have begun to express doubts about the feasibility of these targets. Major players like PG&E, SCE, and SDG&E have cited concerns regarding the loss of federal clean energy tax credits for wind and solar and the influence of growing data center loads as reasons for skepticism toward these achievements.

However, this is not the time for California to back down on its clean energy ambitions. The state has been diligently working to introduce new policies aimed at making the transition smoother and more affordable, such as public financing of major transmission projects and expanding western energy markets through independent governance.

With California’s electricity sector emissions finally on a decline once more, the state must remain committed to its existing goals while continuously identifying and implementing strategies that enhance grid reliability and affordability.