Surveillance and monitoring of pressure drop across completions is critical to any deepwater well that is completed with sand control. Maintaining acceptable velocity across the perforations and sand screens have been discussed to be critical and are derived from the knowledge of pressure drop across each entity. Conventional pressure transient analysis (PTA) which requires the well to be temporarily shut-in is the most applied methodology to calculate that pressure drop. In this paper, an alternate method is proposed that uses Joules-Thomson (JT) heating across the completions to estimate this pressure drop. The method is explored through a case study on a Gulf of Mexico subsea well. The results from the JT method match with results from PTA. The application of JT to determine pressure drop can not only offer continuous monitoring of a well but also provide insight on more challenging situations such as a commingled wellbore with production from two sands. This paper is a discussion of the methodology to use JT for pressure drop calculations across the completions.