EXCLUSIVE: A group of House Republicans led by Rep. David Valadao, R-Calif., wrote a letter Thursday to Democratic California Gov. Gavin Newsom, blasting him for cracking down on diesel-powered trucks.

In the letter, Valadao and seven other GOP representatives from California warned Newsom that his recently-announced plan to electrify heavy vehicles would increase grid instability, especially at times of peak power demand. According to experts, transitioning to electric passenger vehicles and heavy vehicles such as trucks and tractors would require a massive expansion of electric power generation to account for additional grid load.

"While we support continued investment in alternative energy production and more sustainable technologies, the reality is that electric trucks are not yet a viable alternative to diesel and gas-powered trucks, especially given the unreliable capabilities of the state’s electrical grid," the Republican lawmakers stated in the letter first obtained by Fox News Digital.

"In September 2022, California’s electric grid was stressed, and consumers were asked to reduce energy use to avoid rolling blackouts," they continued in the letter. "During this time, the California Independent System Operator said that the state’s grid hit a new all-time record of 52,061 megawatts. While the grid was able to sustain this use thanks to conservation efforts from residents, the demand for energy would have been much greater had thousands of heavy trucks been reliant on power from the state’s grid."

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California Gov. Gavin Newsom

Gov. Gavin Newsom has aggressively pushed for more electrification while shutting down large fossil fuel power that accounts for a large share of current electric generation. (Justin Sullivan/Getty Images)

In addition to Valadao, California Republican Reps. John Duarte, Kevin Kiley, Young Kim, Doug LaMalfa, Tom McClintock, Jay Obernolte and Michelle Steel signed the letter.

The letter came a week after Newsom announced the federal government had granted a waiver approving state heavy-duty truck emission standards that had been proposed by the California Air Resources Board (CARB). 

Under the standards, truck manufacturers will be required to rapidly accelerate sales of zero emission heavy-duty vehicles. By 2035, 75% of new bus and large truck sales, 55% of new small truck sales and 40% of new tractor-trailer sales in California must be electric. By 2045, all new heavy truck sales must be electric under an executive order Newsom signed in 2020.

"This is a big deal for climate action," Newsom said on March 31. "We’re leading the charge to get dirty trucks and buses – the most polluting vehicles – off our streets, and other states and countries are lining up to follow our lead around the world."

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In addition, more than a dozen other states have laws in place that tether their vehicle emissions standards to those set in California, meaning they will replicate the aggressive sales requirements. The states adopting California's truck rule represent 22% of the national truck market.

California Gov. Gavin Newsom holds a power cable before test driving a hybrid Toyota Prius when he was mayor of San Francisco.

California Gov. Gavin Newsom holds a power cable before test driving a hybrid Toyota Prius when he was mayor of San Francisco. (Justin Sullivan/Getty Images)

Overall, the global electric bus stock was estimated to consist of 670,000 vehicles and electric heavy-duty truck stock consisted of 66,000 vehicles in 2021, according to the International Energy Agency. The figures show that 4% of the global bus fleet and 0.1% of the heavy-duty truck fleet was electric. And just 0.1% of truck sales in the U.S. were electric. 

"Governor Newsom is once again putting the interests of extreme environmentalists over hardworking Californians," Valadao told Fox News Digital. "This misguided mandate will make trucking shortages worse, amplify supply chain problems, and further stress California’s electrical grid." 

Valadao's letter Thursday noted that truck drivers are essential for the U.S. economy, moving about 71% of the nation's products. Recent supply chain issues have also been, in part, caused by truck driver shortages. But the letter added that, since electric vehicles are heavier due to the weight of batteries, Newsom's mandate will force drivers to transport lighter loads.

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"According to the California Trucking Association, the additional weight of electric truck batteries could force these heavy trucks to lessen their load capacity by around 8,000 pounds," the letter stated. "This electric vehicle mandate would require more trucks and drivers to transport goods at a time when the trucking industry is already facing a worker shortage of nearly 80,000 drivers."

LOS ANGELES, CA - MAY 06: "u201cI can still smell the diesel exhaust,"u201d says U.S. Sen. Alex Padilla of his time riding LAUSD school buses during a news conference in front of a LAUSD electric school bus on transitioning America"u2019s school bus fleet to electric buses on Thursday, May 6, 2021 in Los Angeles. Padilla and Rep. Tony Cárdenas have legislation, Clean Commute for Kids Act, that would invest $25 billion to replace diesel buses with electric buses. (Photo by Sarah Reingewirtz, Los Angeles Daily News/SCNG)

Sen. Alex Padilla, D-Calif., and Rep. Tony Cárdenas, D-Calif., hold a press conference about the electrification of busses in Los Angeles in May 2021. The two California Democrats, like Newsom, have pushed legislation that would invest $25 billion to replace diesel buses with electric buses. (Sarah Reingewirtz, Los Angeles Daily News/SCNG via Getty Images)

The lawmakers highlighted other issues with mandating electric truck sales including shorter range making them potentially unsuitable for long-haul trips, lack of electric vehicle infrastructure, long recharging times and massive costs that can be expected to be passed on to consumers.

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"We urge you to reconsider CARB’s mandate, and instead work towards a more reasonable and practical approach to sustainable technologies and alternative energy production, while still maintaining the economic viability and success of the State of California," their letter to Newsom concluded.

"These solutions could include promoting more efficient engines and fuel sources such as propane and natural gas and investing in new technologies and infrastructure to make electric heavy equipment more viable. Building a more secure and reliable energy grid would also be a great start to allowing the adoption of these electric technologies."

Newsom's office didn't immediately respond to a request for comment.