Yeah, I have the exact same issue you do. I use a mod to increase the skilling, but there's just no way to leave a sim at home and have them be productive, which is unfortunate. The Sims 4 is incapable of managing more than one lot at a time, and since time keeps going for the entire world, I just accept that I cannot leave one sim upgrading appliances at home while the other goes out.
But if it's just one sim not having energy, you can still leave them at home and set them to take care of their needs. I believe (though I'm not sure, because again I use a mod) that you can tell your sim at home to sleep. I know you can tell them to take care of their needs. Not being able to do anything more with the away sim is the issue I have.
