So continuing into the physics of power and horse power, here is an excellent write up from an excellent book "The How And Why Of Mechanical Movements" (see above post). Don't be scared away by the technical insinuation here, this book is another one of those great books I wish I would have discovered at a younger age. The explanations are clear without a lot of tech speak and lots of illustrations to help clear up the tech speak that there is, lol.
If superconductivity at room temperature can ever be developed in materials that can be used to build motors with, then 100% efficiency will be close. It certainly would be world changing, in everything from the electrical grid to the cellphone in your hand.