One recent study by scientists in EV-friendly Norway has found that in some circumstances electric cars can have a greater impact on global warming than conventional cars.
One of the authors of the report, at the Norwegian University of Science and Technology, Guillaume Majeau-Bettez, admits that he is shocked and disappointed that their findings are not more positive for EVs.
"The electric car has great potential for improvement, but ultimately what will make it a success or failure from an environmental standpoint is how much we can clean up our electricity grid - both for the electricity you use when you drive your car, and for the electricity used for producing the car."
The study is a life cycle analysis of the global warming impact of the production and operation of EVs, driven for 150,000km (93,750 miles), compared with the production and operation of conventional cars. The scientists include so-called "well to wheel" data, taking into account the energy needed to refine and transport oil into petrol or diesel.
One of the findings is that the energy intensive manufacturing of EVs mean that some cars make almost double the impact on global warming as conventional cars. This is mostly because of the raw materials and energy needed to build the lithium-ion batteries.
However, the moment a new EV hits the road, the environmental picture starts to improve.
However, even here the picture is mixed, and wholly dependent on how electricity is generated in the country the car is being driven in.