EVs have zero tailpipe emissions. This means there is no exhaust emitting CO2, NOx or particulates. ICE vehicles such as diesel and petrol ones emit all of these into the atmosphere. This contributes to climate change and poor local air quality.
EVs run on electricity, and there are still CO2 emissions associated with electricity generation.
The amount of emissions depends on how the electricity is generated. For example, generating electricity from burning natural gas produces more emissions than generating electricity from renewable wind power.
So, for every unit of electricity an EV uses, there are CO2 emissions associated with it. But these emissions are still much lower than those from an ICE vehicle.
One way to reduce these emissions is to charge your EV at night when less fossil fuels are used to generate electricity.
As the UK energy grid continues to decarbonise, the associated emissions from EVs will lower.