Energy is everywhere. If there is one principle we hope you will remember and pass on to every person you meet, it is this: to a consumer, such as man, only net energy counts, and this applies to all energy, food and fuel. Gross energy, as a potential, is often very impressive in quantity, but must always be evaluated in terms of the amount that can be converted into the desired work. And thermodynamic costs must be less than the net energy obtained if the conversion is to be a long – term benefit. We have seen that the gross energy of solar radiation is huge, but the net energy of food is very small. Likewise, ‘’proven reserves’’ of oil and coal (‘’enough to last many centuries’’ you may be told) are gross energy. The relevant question is how much will be left to power your car and run your city and what will be the price? If mining, extracting, shipping, and processing oil from under the sea, or that locked in shale rock, requires more energy than the final product is worth, there may be no net energy. Likewise for agriculture; already the energy value of some crops is less than the fuel energy required to produce them. Likewise with atomic energy. The potential energy in the atom is fantastic, but so are the costs of converting it. As with most scientists I was once more enthusiastic than I am today about atomic energy replacing fossil fuels within this century. Costs and difficulties have been greater than our best minds predicted, and we may have invested in the wrong kind of atomic energy, because of our preoccupation with atomic bombs (for more on the kinds of atomic energy). We must continue a massive research effort but it is going to take more time to prove out various possibilities for harnessing atomic energy on the scale we now extract energy from fossil fuels. Which means that we should ‘’power down’’ and be fore efficient in the use of ‘’proven net energy’’ at least for a while.
Most convenient and worthwhile uses of energy

        To put some of this in perspective let us consider the fuel – energy budget of the united states as of the early 1970s. from the large world reserves of fossil fuel energy the united states receives about 16.1010¹⁵ kcal/year, but only about half (50 percent) is actually converted into useful work. Thus, the ‘’net’’ is 8, not 16.10¹⁵, not quantities in the ground. Cost of extracting and processing goes up as gross supplies dwindle and we have to turn to lower quality materials. Two of our most convenient and worthwhile uses of energy are automobiles and electricity. But are about 30 percent efficient which contributes to the low overall efficiency. It seems likely that the 1970s will see us give up some convenience to improve efficiency and thus stretch out fuel energy supplies as they become more expensive to convert from gross reserves. We have already spoken of need for diversification in situations such as this.

        There is a parallel of sorts in economies. For many years the gross national product (GNP) has been considered a good index of economic well – being. Now, many economists are suggesting that net economic worth (NEW) would be a much better measure. In computing NEW the ‘’bads’’ (pollution costs, and so on), as well as the ‘’goods’’ (manufactured product, and so on) are considered, and maintenance work. Such as the work of the housewife, is included. In recent years the GNP of most nations has been going up the NEW for the united states has leveled off, indicating that the real economic situation has been improved by ever larger production of hard goods.