Nonionic surfactant concentration can have a large impact on the temperature-dependent behavior of Surfactant-Oil-Water (SOW) systems. One of the limitations of commonly reported Hydrophilic-Lipophilic Deviation (HLD) modeling approaches is the lack of accounting for this concentration dependency. In this paper, quantitative relationships between alcohol ethoxylate concentration and SOW phase inversion temperature (PIT) will be reported in the context of HLD model parameterization. Dynamic temperature scan methods will be described that enable facile determination of PIT vs. surfactant concentration functions. Conversion of PIT data into to HLD parameter functions will also be described, together with the application of resulting HLD models to practical formulation problem solving such as oil solubilization and emulsion stability optimization.