Even a third might be being generous. I have never once really broken a sweat riding an eBike even in hot summer weather. I've actually had to put jackets/jumpers on to stop the wind chill on hot days - this never happens on normal bikes due to the effort exerted.

This however is precisely why I have some ebikes in addition to human steam powered ones - its so nice for commute or journeys when you want to arrive feeling refreshed but not need a shower or change of clothes.