Assessing the environmental impacts of electric vehicle adoption in North Island and South Island, New Zealand

Limited studies have assessed future New Zealand (NZ) transport emissions under different electricity mixes and EV deployment using the life cycle assessment (LCA) approach. Unlike national-level studies, this work integrates disparities in the electricity system to evaluate the environmental implications of EV adoption across the North and South Islands during the use phase. NZ faces unique challenges due to its distinctive geographic and energy-generation characteristics. The North Island’s electricity mix relied on 45% of non-renewable sources, while the South Island was powered by 100% renewable energy in 2020. The results indicate a significant difference in decarbonisation potential, with EVs emitting 5 times more CO 2 eq/km in the North Island (0.043 kg CO 2 eq/km) than in the South Island (0.008 kg CO 2 eq/km). The emissions trade-off arises because inter-island transmission benefits the North Island but poses a drawback for the South Island. In the scenario analysis, cleaner energy sources coupled with rapid EV uptake significantly mitigate both islands' global warming potential (GWP), fine particulate matter formation potential, and fossil resource scarcity potential, except ecotoxicity from non-exhaust emissions (brake and tyre wear) remains a challenge. The sensitivity analysis reveals that battery replacements can escalate ecotoxicity by up to threefold and become a primary GWP contributor in the South Island, which has a low operational GWP. Furthermore, a 20% improvement in vehicle energy efficiency reduces CO 2 emissions by 16% in the North Island and 10% in the South Island, highlighting that technological evolution provides greater benefits in fossil-dependent regions.