On my own bike, I don't think there is a pace that isn't easier. Even at slow speeds, it's not a whole lot of work. (And you can always change to a gear where it just isn't a lot of work to go slow. The challenge is more remaining upright, but a low gear and the barest of forward momentum will help that.)
… I dunno. Bikes aren't just efficient, they're the most efficient form of human movement. 60 W gets you 3 mph walking or 9 mph biking.
https://en.wikipedia.org/wiki/Bicycle_performance
On my own bike, I don't think there is a pace that isn't easier. Even at slow speeds, it's not a whole lot of work. (And you can always change to a gear where it just isn't a lot of work to go slow. The challenge is more remaining upright, but a low gear and the barest of forward momentum will help that.)