There are two levels of compatibility, "compatible" and "UL certified". For inverters, you can look in our Downloads area under Certifications and Compliance. This is by inverter manufacturer. This level of compatibility means that the products have been tested by Tigo and/or the inverter manufacturer and found to work as designed. UL listing and certification involves much more rigorous testing and involves UL, Tigo and the inverter manufacturer. We have a list of UL PVRSS Certified Inverters on our website. For PV modules, the power ratings, cable lengths, cable connectors and physical fit should be checked. Details can be found in the article, "How do I check compatibility with Tigo TS4 products?". UL listing is not needed for PV Modules with Tigo TS4.