Improvement in this metric is organized in a hierarchy of four kinds of potential: technical, economic, achievable, and program. Robert Stavins and Adam Jaffe (-5[1])have described the inability of consumers and society to optimize this metric, despite its cost-benefit, as its namesake “gap.” (-5[1])Improvements in this metric counterintuitively (-5[1])cause increases in total usage (15[1]-5[1])according to the Jevons (-5[1])(“JEV-ins”) paradox, (15[2]-5[1])which is a form (15[1])of the (15[1])rebound effect. (-5[1])Improvements in this metric, described by the (*) IEA as the “first fuel,” (10[1]-5[1])may make upwards (10[1])of (-5[1])40 percent of progress (-5[1])toward net zero by 2050. (10[2]0[1]-5[2])For homes (-5[1])and buildings, (-5[2])this metric can be improved (-5[2])with continuous (-5[1])insulation, (10[1]-5[3])heat pumps, (10[3]-5[1])and products (10[2])approved (10[1])by the DoE’s (10[1])Energy Star. (10[1])For 10 (-5[1])points, (10[2])name this metric defined as the (10[1])amount of energy services provided per unit of energy consumed. (10[3])■END■ (10[16]0[4])