In this chapter, we tackle the challenge of determining energy metrics for individual reactions and synthesis plans. Based on standard practices in reporting experimental procedures, the disclosure of essential data necessary for a proper determination of energy consumption for carrying out an individual chemical reaction is essentially relegated to reaction temperature and reaction pressure (the latter is particular for industrial reactions for first and second-generation feedstocks). A proper determination of energy consumption involves the following components: (a) a complete data set of thermodynamic parameters for all input materials involved in a chemical reaction: reactants, solvents, catalysts, and any other additives; (b) reaction temperature and reaction pressure; and (c) electricity consumption for all operational procedures requiring equipment such as heating and cooling apparatuses, mixers, rotatory evaporators, vacuum pumps, and so on. The latter contribution from operational procedures is completely absent from experimental procedures and so we focus our attention on estimating energy consumption from the first two contributors. The key thermodynamic parameter sought after is the change in enthalpy for each input material, q input, i , which is made up of a temperature component and a pressure component. The temperature and pressure contributions arise from the respective temperature and pressure changes from ambient standard conditions of 298 K and 1 atm (state 1) to the reaction conditions of T rxn and P rxn (state 2). The temperature contribution requires knowledge of temperature and phase dependent heat capacity functions for each input material. The pressure contribution requires knowledge of an appropriate equation of state for fluids (gases and liquids) applicable to each input material. Figure 5.1 shows a flowchart that tracks the logic and strategy of arriving at the overall change of enthalpy for all input materials in a chemical reaction according to the relationships given in Equations (5.1) and (5.2). A flowchart showing how to determine the enthalpy change for each input material in a chemical reaction from state 1 (298 K, 1 atm) to state 2 (<italic>T</italic> <sub>rxn</sub>, <italic>P</italic> <sub>rxn</sub>). https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429400681/1c7c4d69-b8a6-4a01-93e0-8b9919282213/content/fig5_1_B.tif"/> q input , i = | q temp , i | + | q press , i | https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429400681/1c7c4d69-b8a6-4a01-93e0-8b9919282213/content/TNF-CH005_eqn_0001.tif"/> Δ H = ∑ input , i q input , i = ∑ input , i | q temp , i | + ∑ input , i | q press , i | https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429400681/1c7c4d69-b8a6-4a01-93e0-8b9919282213/content/TNF-CH005_eqn_0002.tif"/>