They shall also set forth the location, rated capacity and actual power output of all power plants owned or operated by the applicant, whatever the motive power thereof may be; the location of all water power sites, whether developed or undeveloped, owned or operated by the applicant, and the power, or additional power, which may be obtained by a proper and economical development effected at each such developed or only partially developed site; what developments, extensions or enlargements, if any, of said sites or plants are planned or under consideration by the applicant; the markets supplied by existing plants; the relationship, if any, of the applicant's existing plants to the project in connection with which a license is sought from the commission, and the relationship, if any, of the project plant to any other hydro-electric plants.