(a) Gas utility rates shall be based on the adjusted value of invested capital used and useful to the utility in providing service and that adjusted value shall be computed on the basis of a reasonable balance between:
(1) original cost, less depreciation; and
(2) current cost, less an adjustment for present age and condition.
(b) The regulatory authority may determine a reasonable balance that reflects:
(1) not less than 60 percent nor more than 75 percent of the original cost of the property at the time the property was dedicated to public use, whether by the gas utility that is the present owner or by a predecessor, less depreciation; and
(2) not less than 25 percent nor more than 40 percent of the current cost less an adjustment for present age and condition.

(c) In determining a reasonable balance, the regulatory authority may consider inflation, deflation, quality of service being provided, growth rate of the service area, and need for the gas utility to attract new capital.
(d) Construction work in progress, at cost as recorded on the gas utility’s books, may be included as part of the adjusted value of invested capital used by and useful to the utility in providing service, as necessary to the financial integrity of the utility.
(e) Costs of facilities, revenues, expenses, taxes, and reserves shall be separated or allocated as prescribed by the regulatory authority.
(f) In this section, “original cost” means the actual money cost or the actual money value of consideration paid other than money.