Electric cars are up to four times better for the environment when being driven in New Zealand than in Australia.
Massey University Professor Ralph Sims is part of the Intergovernmental Panel on Climate Change, and said because electricity generation in New Zealand was mostly renewable, it was one of the best countries to own an electric vehicle in.
That information could help shape the thinking of consumers who were looking to upgrade their car in 2020, he said.
"Electric cars are far more efficient in terms of greenhouse gas emissions if the electricity is renewable electricity," Sims said.
"In New Zealand, 80-85 percent of electricity is renewable, and therefore the emissions per kilometre or per passenger kilometre are a lot lower with an electric vehicle than they would be for a petrol or diesel vehicle.
"If on the other hand that electric vehicle's running in Australia, or China or other countries where coal fired power is where the electricity comes from, then you can actually produce more greenhouse gas emissions per passenger kilometre because of the form of generation.
"So from New Zealand's point of view, it's a real advantage having an electric vehicle in terms of the emissions from the fuel from the electricity."
An electric vehicle run in New Zealand emits between 30 and 40 grams of carbon dioxide per passenger kilometre travelled.
By comparison, a comparative petrol car emits between 130g and 170g, and a diesel car emits between 120g and 150g of carbon dioxide per passenger kilometre travelled.
In Australia, that same electric car would emit between 80g and 130g of carbon dioxide per passenger kilometre travelled.
Sims said a further study by the IPCC looking at the entire life cycle of an electric vehicle was due out in 2022.
That would include the expected life of the vehicle, battery recycling and more.
Recycling of batteries used in electric vehicles had only just started - and was not yet available in New Zealand - but would improve the emissions of an electric vehicle even further, Sims said.
"About 90 percent of the materials and chemicals in the battery can be reused in new batteries.
"So that's the sort of overall analysis which has to be done, so it's not just the fuel, it's the overall use of the batteries as well."
People could do all they wanted to reduce emissions, but one flight to Europe would blow everything out of the water.
One seat on a flight to Europe from New Zealand accounted for about a year's worth of carbon dioxide emissions from a petrol vehicle.
But flying was sometimes the better option when travelling in New Zealand, he said.
"If the plane's say a 150-seater Boeing which is the sort of plane that buzzes up and down between Wellington and Auckland, and if it's full or near full, then it's about 90 grams of carbon dioxide per passenger kilometre.
"From the emissions point of view, if a car drives up from Wellington to Auckland, and if it's the largest car, which we tend to use in New Zealand, and therefore produces more greenhouse gases, then it can be a lot more emissions - almost doubled in some instances - compared to catching the plane.
"But then of course, you've also got to get to the airport in a taxi or whatever as well. So you've got to add that into the total journey.
"But electric vehicles are still the best way to go in terms of reducing greenhouse gas emissions."
Although little used, the best way to travel around the country from an emissions standpoint was rail, which could be up to eight times better than an electric car.
RNZ
