The utilities board shall consider the petition and any objections filed to it in the manner provided. It shall examine the proposed route or cause any engineer selected by it to do so. If a hearing is held on the petition it may hear testimony as may aid it in determining the propriety of granting the franchise. It may grant the franchise in whole or in part upon the terms, conditions, and restrictions, and with the modifications as to location and route as may seem to it just and proper. Before granting the franchise, the utilities board shall make a finding that the proposed line or lines are necessary to serve a public use and represents a reasonable relationship to an overall plan of transmitting electricity in the public interest. A franchise shall not become effective until the petitioners shall pay, or file an agreement to pay, all costs and expenses of the franchise proceeding, whether or not objections are filed, including costs of inspections or examinations of the route, hearing, salaries, publishing of notice, and any other expenses reasonably attributable to it. The funds received for the costs and the expenses of the franchise proceeding shall be remitted to the treasurer of state for deposit in the commerce revolving fund created in section 546.12 as provided in section 476.10.