Prius seldom runs on batteries alone?
 

I rode in a friend's Prius and he showed me that the engine started up
before he hit 5 mph even under mild acceleration. I thought the
difference between the "full" hybrids like Prius and "mild" hybrids
like the Civic was the ability of the former to operate as a pure
electric over a modest range of conditions. It would seem that the
Prius' all electric performance is very modest indeed. Is this
correct?