If you’ve had any doubt about the effectiveness of electric vehicles in the face of climate change, doubt no more.

At least, that’s the implication of a newly released University of Hawaii study that suggests that the faster Oahu can transition to electric vehicles, the greater the dent will be in consuming fossil fuels and generating carbon dioxide emissions.

“The magnitude of it I found surprising,” said Katherine McKenzie, a faculty member with UH’s Hawaii Natural Energy Institute and author of the study. “I didn’t know it would be that dramatic.”

Under the most ambitious scenario devised by McKenzie, the combination of faster adoption of electric vehicles and faster generation of renewable energy resulted in 99% less fossil fuel consumed and 93% fewer CO2 emissions from passenger and freight vehicles on Oahu by 2050.

In an article published in World Electric Vehicle Journal, McKenzie created mathematical models of four scenarios based on projections for the transition to electric passenger and freight vehicles and renewable power generation.

After quantifying the impacts of fossil fuel use and CO2 emissions on Oahu, she found that scenarios with a slower transition to electric vehicles result in billions more gallons of gasoline consumed and tens of millions more tons of CO2 emitted.

While the overall trend seems intuitive, no one had really crunched the numbers before to see what the actual impact EVs would ultimately mean for oil- dependent Oahu.

What’s more, there remained lingering doubts about electric vehicles and whether they offer enough to substantially cut into the island’s carbon dioxide emissions and fossil fuel use.

After all, EVs run on electricity that is largely produced on the island from fossil fuels, and a substantial amount of energy goes into the manufacture of the vehicles and their batteries.

McKenzie, however, found that average passenger EVs in 2020 consumed the equivalent of 66 gallons of gasoline — or seven times less fossil fuel than gasoline- powered vehicles, which used 455 gallons. Average EVs also cut emissions in half — two metric tons of CO2 versus four metric tons of CO2 in 2020 alone.

Despite the island’s high dependence on oil for power generation, the acceleration of both EV use and grid renewables will have striking benefits over the coming years in steeply reducing both fossil fuel use and emissions, McKenzie said.

“We need to switch to electric vehicles as fast as we can. There’s no doubt whatsoever,” she said.

Continuing to purchase anything powered by petroleum locks in emissions and energy insecurity for years to come at a time when decarbonization is a climate imperative, McKenzie said.

In addition, a shift is needed to energy-efficient modes of travel, including more bicycling, walking and transit use, along with reducing vehicle miles traveled through “smart” city planning and remote work, for example, she said.

McKenzie said she hopes government and other decision makers will consider the study’s scenarios to better understand future uncertainties, develop strategies and inform the development of policy.

The number of passenger EVs in Hawaii continues to grow, according to the state Department of Business, Economic Development and Tourism, but they still comprise only 1% of the roughly 1 million registered passenger vehicles in the state.

McKenzie on Tuesday will present results from her study — “EVs on the Grid: Impacts, Challenges & System Stability Risks,” — at an online conference, “Utility Planning for Electric Vehicles on the Grid.”