Are promises more efficient than observables?

I've been learning about promises and observables recently. I found a lot of good information about the feature differences, but I was wondering if there were any performance / efficiency implications between promises and observables?

Note: I also looked through this post: Promise vs Observable but I didn't see any mention about efficiency.

There aren't any performance differences, they're just different paradigms for returning data as Promises return once but Observables return data like a stream.