This fact sheet presents three in situ test methods for solar collectors and solar collector arrays, namely In situ Collector Certification (ICC), Performance Check for Collector Arrays (PC) and Dynamic Collector Array Test (D-CAT). A comparison is made regarding their scopes and use cases, methodologies and outcomes, which could serve as a decision-making aid for stakeholders in selecting the procedure that best suits their needs. The analysis shows that the methods do not contradict, but rather complement each other.