As utilities plan future cost-of-service rate studies they need to understand the benefits and difficulties that may be encountered when computer models are used. This paper demonstrates the capabilities of computer models that relate to pricing issues by describing development of a model for the El Paso Water Utilities. The paper also describes the difficulties the utility had using the model, as well as the model's benefits. The El Paso Water Utility looked into reducing water use through its water rate structure. However, the utility was concerned about the impact of significant rate increases on low-income persons, and it wanted to address other traditional cost-of-service concerns like equity in cost allocation, maintaining financial sufficiency, and ensuring compliance with debt coverage requirements.