NEP is an acronym for 'Net Energy Profit, ' which is a term used in the energy industry to describe the amount of energy produced by a system that exceeds the amount of energy required to operate it. CATNIP is a six-letter word that is related to NEP, as it stands for 'Cost Analysis Tool for Net Energy Profit.' This tool is used to analyze the cost of energy production and consumption, and to determine the net energy profit of a system.