Upgrading clean energy fuels, such as biogas, natural gas, and shale gas, requires the capture of CO2 to enhance their heating value. Ionic liquids (ILs) are promising absorbents for this purpose, but the vast number of available ILs necessitates an efficient screening method. The Comparative Absorption Factor (CAF) developed in our previous study can estimate the total annual cost (TAC) of CO2 capture from biogas, which is a key advantage over alternative screening methods. However, CAF does not consider the effects of operating conditions such as CO2 concentration, pressure, and temperature. To address this limitation, a modified CAF (CAFmodified) that incorporates these factors was proposed. Given the linear relationship between the original CAF and TAC, three representative ILs ([C10mpy][DCA], [C1mim][tfo], and [C1py][tfo]) were selected from 490 ILs based on their melting point, viscosity, and original CAF values. Subsequently, process simulations for these ILs were conducted using Aspen Plus, considering a wider range of operating conditions: CO2 concentrations of 30–50 vol%, temperatures of 303.15–318.15 K, and pressures of 7–15 bar. These simulations were used to determine the Aspen Plus-derived TAC, which served as the basis for proposing CAFmodified. Finally, data for Aspen Plus-derived TAC from the previous study and for 6 additional ILs over a broad range of operating conditions were used to compare with the TAC values estimated by CAFmodified. The results showed an average relative deviation of 16%, indicating that CAFmodified is effective for screening ILs for CO2 capture under varying operating conditions.