New Study Shows a Rapid Increase of Diesel-Fueled Backup Generators Across California

By October 11, 2021 5   min read  (911 words)

October 11, 2021 |

Fuel Cells Works, New Study Shows a Rapid Increase of Diesel-Fueled Backup Generators Across California

Research reveals the environmental dangers posed by diesel-fueled generator emissions threaten public health and create significant hurdles to achieving greenhouse gas reduction targets

SAN JOSE, Calif. New research by economic and public policy consulting group M.Cubed finds a proliferation of backup generators across California, with nearly 90 percent being diesel-fueled, posing significant obstacles to achieving greenhouse gas reduction targets and driving nearly $136 million in annual health costs.

Over the last year, the generator population jumped by 22 percent in the South Coast Air Quality Management District (SCAQMD), and by 34 percent in the Bay Area Air Quality Management District (BAAQMD) over the last three years. In 2021, the two districts were collectively home to 23,507 backup generators with a capacity of 12.2 gigawatts (GW), about 15 percent of California’s entire electricity grid. Of these, 20,907 are diesel-fueled.

Diesel generators release greenhouse gases, particulate matter (PM), volatile organic compounds (VOCs), nitrous oxides (NOx) and sulfur dioxide (SO2), harmful pollutants that create smog and exacerbate respiratory conditions.

The report concludes that diesel generators in the South Coast and Bay Area communities alone have 12.2 GW of generation capacity and produce roughly 20 metric tons (MT) of fine particulate matter, 62 MT of VOCs and almost 1,000 MT of haze-inducing NOx annually.

“We have long been concerned about the proliferation of diesel backup generators here in the Bay Area, as highlighted in this report,” said Jack Broadbent, executive officer of the Bay Area Air Quality Management District. “Emissions from these backup generators can harm local residents, regional air quality and the global climate. This is particularly true in communities already overburdened by air pollution and the Air District is actively pursuing regulations to curb this pollution.”

This pollution, in turn, may trigger upwards of $31.8 million in annual health costs in the Bay Area and $103.9 million in South Coast communities, due to increases in mortalities, heart attacks, hospital visits and other adverse consequences – particularly in vulnerable communities.

“This research began when I received a notice that a diesel-fueled generator was being sited near my daughter’s high school,” said M.Cubed partner and lead researcher Steven Moss. “I never expected to find so many diesel-fueled generators operating in San Francisco and across the state of California, especially so close to where people live, work, and play. For a state leading in climate action, this growing reliance on diesel underscores a disconnect between how we’re addressing grid reliability, long-term energy affordability, and the ongoing environmental consequences of diesel dependency.”

Diesel generators tend to be located close to where people live, work and attend school. Importantly, M.Cubed’s study highlights that many of these generators are in communities that the California Environmental Protection Agency identifies as “disadvantaged,” according to CalEnviroScreen. Considering environmental conditions and community members’ vulnerability to a degraded ecosystem, CalEnviroScreen is a method to evaluate multiple pollution sources in a geographically defined area that accounts for the population’s sensitivity to pollution’s adverse effects.

“It is concerning to see an increased reliance on diesel-fueled generators, particularly when nearly three-quarters of California voters support alternative, non-harmful energy solutions like fuel cells and more than half desire to see diesel generation reduced,” said Marisa Blackshire, senior director of environmental compliance, Bloom Energy. “We must embrace existing technologies that will make California’s grid cleaner and more resilient, rather than increasing the population of high-polluting power sources that will set us back in meeting crucial emission reduction goals.”

For example, in the South Coast, 47 percent of generators are in the most vulnerable communities, classified as being in CalEnviroScreen’s 80th to 100th percentile, with 33 percent above the 90th percentile.

“California’s growing dependence on diesel-fueled backup generators is a clear but alarming response to the state’s worsening wildfires and our efforts to manage them,” said Carl Guardino, executive vice president of government affairs and policy, Bloom Energy. “In addition to carbon emissions, diesel releases dangerous amounts of particulate matter, volatile organic compounds, nitrous oxides and sulfur dioxide. These pollutants create smog, which exacerbates respiratory conditions, such as asthma, chronic obstructive pulmonary disease, and lung cancer, especially in children and older adults.”

In California, diesel generators are individually permitted by each of the 35 air districts in which they are located, so data on the cumulative population is largely unavailable. Data from individual districts is not aggregated or reported at the state level, and backup generator usage data and permit renewals are self-reported by the operators themselves. As a result, this data remains largely hidden and subject to little regulatory scrutiny.

M.Cubed’s full report on the BAAQMD and SCAQMD records of diesel backup generators can be found here:

About M. Cubed

M.Cubed, founded in 1993, provides economic and public policy consulting services to public and private sector clients. Practice areas include water and energy utility resource planning and ratemaking, resource use efficiency and conservation measures, project impact analysis, regional economic modeling, natural resource allocation policies, and environmental plan preparation and review

About Bloom Energy

Bloom Energy’s mission is to make clean, reliable energy affordable for everyone in the world. Bloom’s product, the Bloom Energy Server, delivers highly reliable and resilient, always-on electric power that is clean, cost-effective, and ideal for microgrid applications. Bloom’s customers include many Fortune 100 companies and leaders in manufacturing, data centers, healthcare, retail, higher education, utilities, and other industries. For more information, visit

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