Even though both fixed and variable components exist for energy consumption, the most straightforward benchmark approach considers energy as a variable input. This simplification assumes that most plants in an industry are operating well above 50% capacity utilization, where energy consumption typically varies with production rate in a linear way. It is true that a typical production plant will still consume substantial energy even at very low capacity utilization. The most efficient energy use is usually when the plant is running at a very high rate, just as with many other operating parameters.