A certificate may not be issued unless the commission finds that the applicant is fit, willing, and able to provide the utility services applied for and that the services are required for the convenience and necessity of the public. The commission may issue a certificate granting an application in whole or in part and attach to the grant of it the terms and conditions it considers necessary to protect and promote the public interest including the condition that the applicant may or shall serve an area or provide a necessary service not contemplated by the applicant. The commission may, for good cause, deny an application with or without prejudice.