Establishes methods for determining the thermal performance of glazed liquid heating solar collectors; provides test methods and calculation procedures for determining the steady-state and quasi-steady-state thermal performance of solar collectors. Contains methods for conducting tests outdoors under natural solar irradiance and indoors under simulated solar irradiance. Not applicable to those collectors in which the thermal storage unit is an integral part of the collector to such an extent that the collection process cannot be separated for the purpose of making measurements of these two processes. Also not applicable to unglazed solar collectors nor is it applicable to tracking concentrating solar collectors.