The decline in overall efficiency in the US economy mainly has to do with the increasing role of inefficient energy systems. Specifically, the years since 1970 have seen a substantial increase in electricity consumption and private vehicles for transportation, two energy services that are particularly inefficient. (Electricity wastes two-thirds of its primary energy; transportation wastes about three-quarters.)
There is loss inherent in any system that converts raw materials to usable energy, or transports or uses energy, of course. That follows from the second law of thermodynamics. And it’s true both narrowly (a car is an energy system) and broadly (a city is an energy system). It’s not possible to achieve perfect efficiency, or anything close to it.
But surely we can do better than 31 percent! Sixty-six quads is a truly mind-boggling amount of energy to vent into the atmosphere for no good purpose.
It really highlights the enormous potential of better-designed systems — especially better electricity and transport systems, along with better urban systems (i.e., cities) — to contribute to the country’s carbon reduction goals. We could double our energy use, with no increase in carbon emissions, just by halving our energy waste.