Yeah, very important to electrify the supply side in the US as well. Pretty dirty at the moment. There are still gains to be realized just on the demand side though, like how EVs still emit less per mile than ICE cars even when the electricity comes from coal plants[0]. In that case, the efficiency comes form the improved thermal efficiency of an industrial-scale power plant versus little gasoline car engines.
[0] - would have liked a better source but https://www.bloomberg.com/news/articles/2019-01-15/electric-...