Let's put the difference between energy input and output into an analogy everyone can understand. Suppose you go to your favorite pub and order 5 pints of beer. The bartender puts them up on the bar and you proceed to drink 1 and pour the other 4 out into the nearest sink. After you drink your beer you say, "I'm still thirsty," and order 5 more. Once again, you pour 4 down the sink and drink 1. At the end of your pint you decide to go home. As you pay for your pint you notice that it takes $40 to pay for your pints, instead of the usual $8. Nevertheless you pay for your beer, tip the bartender and get into your automobile which is powered by an internal combustion engine that is just as wasteful as your behavior in the bar. On the drive home you ponder just what "20% efficiency" really means.
Insisting we get more work done by using internal combustion engines without factoring in how much energy is wasted AND refusing to consider where the wasted heat and gases go is an example of puerile thought processes. Ditto for willfully confusing input and output. When we burn fossil fuels we burn up calories. When we walk around and dig ditches and weed carrots and sit in front of a computer, we burn up calories. Since I have delineated my methodology several times on this blog, I won't repeat it here. What I will say is that you burn up around 2500 calories a day for a US male and around 2000 for a US female. If you grow some food with your calories, you get a much better return on the energy invested than if you sit behind the wheel of your car or in front of your computer. In the future, when the real cost of energy will be accounted for in the marketplace, you will realize that deep in your heart and in your hands.