N.J. Stat. § 48:2-18
The board may, after hearing, upon notice, by order in writing, require every public utility to carry, whenever in the judgment of the board it may reasonably be required for the protection of stockholders, bondholders or creditors, a proper and adequate depreciation account in accordance with such rules, regulations and forms of account as the board may prescribe.
The board shall from time to time ascertain and determine, and by order in writing after hearing, fix proper and adequate rates of depreciation of the property of each public utility in accordance with such regulations or classifications. Such rates shall be sufficient to provide the amounts required, over and above the expense of maintenance, to keep the property in a state of efficiency corresponding to the progress of the industry.
Each public utility shall conform its depreciation accounts to the rate so ascertained. Amounts so provided shall not be expended otherwise than for depreciation, improvements, new construction, replacements, extensions or additions to the property of the public utility or for the retirement of debt incurred in connection therewith.
N.J.S. § 48:2-18