Taiwan has been developing clean energy and solar heating for hot water production is a mature technology. The subsidy program (2000-2016) for solar water heaters means that the cumulative area of solar collectors installed was approximately 2.52 million square meters at the end of 2016, in which more than 93% have been installed in the domestic sector. Industrial heat processes represent an area for solar thermal application. This study presents field measurements for solar water heaters installed for sterilization in dairy industry. Global solar radiation can be correlated with the system’s thermal efficiency reasonably well. As a pre-heating system, financial viability is validated.