1. The commission shall have power, after hearing, to require any or all gas corporations, electrical corporations, water corporations and sewer corporations to carry a proper and adequate depreciation account in accordance with such rules, regulations and forms of account as the commission may prescribe.

2. The commission may, from time to time, ascertain and determine and by order fix the proper and adequate rates of depreciation of the several classes of property of such corporation, person or public utility. Each gas corporation, electrical corporation, water corporation and sewer corporation shall conform its depreciation accounts to the rates so ascertained, determined and fixed, and shall set aside the moneys so provided for out of earnings and carry the same in a depreciation fund and expend such fund only for such purposes and under such rules and regulations, both as to original expenditure and subsequent replacement, as the commission may prescribe. The income from investments of moneys in such fund shall likewise be carried in such fund.