Separate accounts shall be kept for each public utility owned or operated by the city, distinct from other city accounts, and in such manner as to show the true and complete financial result of such city ownership or operation, or both, including all assets, liabilities, revenues, and expenses.  These accounts shall show the actual cost to the city of each such public utility, the cost of all extensions, additions, and improvements, all expenses of maintenance, the amounts set aside for sinking fund purposes, and all operating expenses.  They shall show as nearly as possible, the value of any service furnished to or rendered by any such public utility by or to any other city department.  They shall also show a proper allowance, for depreciation and insurance.  The council shall annually cause to be made a report showing the financial results of such city ownership or operation, or both, which report shall give for each utility, the information specified in this section, and such further information as the council shall deem expedient.