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At least in China it will take quite some time before e-cars will be better for the environment.
It very much depends on the country you are in whether e-cars are environmentally efficient. In most countries, for the time being at least, you should only change to an e-car if you would sell your old gas guzzler anyway & if you really use your car a lot. (& if you don't need a car regularly, don't buy one.)