I think it all depends on how you view efficiency. According to Wikipedia

“Efficiency is the (often measurable) ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without waste.”

I was thinking about Henry David Thoreau. I would say at his time in Walden he lived a remarkably efficient life in terms of he avoided wasting money and time having to work a lot to pay for rent or expensive foods, since he built his own house and grew beans. I’m sure he had more time free to do what he wanted to do (read, write, walk, meditate, swim, talk to people, observe nature) because he really figured out the most efficient way to live. For him that was a path of radical simplicity. I think simple living and efficiency are directly linked.

You only have to read his writings about how most people house themselves to realise that his cabin was an exercise in the most efficient housing possible.

Just my opinion on the subject...