This is according to a study by researchers from the University of Auckland and Xiamen University in China, published in the journal Energy.

The researchers analysed the environmental impacts of human activity and used a robust statistical approach to investigate what drives a nation's carbon dioxide (CO₂) emissions.

Using data from 26 countries over 15 years, they found a surprising trend: higher EV uptake was linked to increased CO₂ emissions. The reason? In a number of countries, EVs are still being powered by electricity generated through burning fossil fuels like coal or oil.

Associate Professor Stephen Poletti and Simon Tao, a doctoral candidate at the Business School's Energy Centre, didn't observe a significant reduction in CO₂ emissions globally due to EV adoption.

"On the contrary, EV adoption is positively associated with CO₂ emissions," says Tao. "This finding appears counterintuitive; it challenges the conventional belief that EVs contribute to decarbonisation.

"Our analysis highlights that the environmental benefits of EVs are contingent on the composition of a country's electricity generation mix.”

Take EVs charged using electricity from coal-fired power plants, says Poletti.

“In that case, they may indirectly contribute to higher emissions than modern gasoline or diesel vehicles, especially considering the entire lifecycle from production to disposal."

The study results suggest only when the global share of renewable electricity generation reaches approximately 48 percent will electric vehicle adoption contribute to reducing CO₂ emissions.

Renewable energy, mainly wind, solar and hydro, accounted for only a little more than 30 percent of the world's electricity in 2023, so there's a way to go, says Poletti.

"Electric vehicles are often seen as a silver bullet for climate change, but our results show that's not the case if the electricity powering them isn't clean.”

New Zealand, where over 80 percent of electricity generation is renewable, is well-placed to reap the benefits of EVs. Across the ditch, a Clean Energy Council report found that renewables overall accounted for nearly 40 percent of Australia’s total electricity supply in 2023.

"This research is a reminder that decarbonising transport can't happen in isolation," says Poletti.

"EVs are only as green as the grid they plug into, and government policies should aim to increase the adoption and integration of renewable energy like solar and hydro. This can be achieved by setting ambitious renewable energy targets and providing adequate subsidies such as tax credits to producers and consumers of renewable energy.”

Poletti says investments in smart grids and transmission networks can boost the efficiency and reliability of renewable energy supply.

“Policies should support community-based renewable energy projects, which can increase public acceptance of renewable energy installations."

Further, the researchers say eliminating subsidies for fossil fuels and implementing carbon pricing mechanisms could also incentivise renewable energy development.

“Electric vehicle uptake can help countries meet climate-related targets, as long as the energy used to power them is clean,” says Tao.

In addition to EV uptake, the researchers examined the impacts of economic growth, green technology innovation, renewable energy consumption and population density on emissions.

They found that economic growth increases emissions, while innovation in environmentally friendly technology and population density, in the form of more compact cities, can help lower them. Renewable energy use had the most significant emissions-reducing effect.