Determining the thermal capacity of evaporative condensers has long been left to theory, "rules of thumb," or the guarded operations of manufacturers' test laboratories. Now, modern instrumentation and test methods make field-testing of evaporative condensers practical, accurate, and readily available to owners, engineers, and manufacturers alike. Field-testing gives owners the ability to confirm manufacturers' performance guarantees on new equipment and also to determine the current capacity of existing installations. To demonstrate the practicality and accuracy of field-testing, a series of thermal capacity tests were performed in both the controlled environs of a thermal laboratory and at an operating industrial refrigeration facility. This study presents the testing methods used and an analysis of the test results, based on standards from ASHRAE, ARI, and CTI. This series of tests demonstrates that field-testing of evaporative condensers is both practical and accurate. Field-testing can be used to accurately assess the performance of evaporative condensers, new and existing.