This ANSI-approved standard establishes minimum criteria for the design and installation of solar water heating systems. It describes requirements for solar water heating system design and evaluation. The requirements in the ICC 900/SRCC 300-2020 update and expand the previous edition to include photovoltaic water heaters, consolidate marking and labeling, and clarify electrical and fire safety requirements. This latest version has been correlated for consistency with the latest model plumbing and mechanical codes in use.