The author seems to have discovered why 95% of people were peasants in pre-industrial societies.

You can't just casually grow enough food to provide a full diet for yourself.

With domestic robots coming in the near future (with any luck), thinking about labor in this way is going to be grossly misleading. Thinking about land is still relevant, however. As for energy, if given enough land for solar energy, it can be accounted for. In short, land availability would be the primary limiting factor for self-sufficiency.