As used in this chapter: “Allowed distribution revenue” means the average annual, weather-normalized, nongas commodity revenue per customer associated with the rates in effect as adopted in the applicable utility’s last Commission-approved rate case or performance-based regulation plan, multiplied by the average number of customers served. “Conservation and ratemaking efficiency plan” means a plan filed by a natural gas utility pursuant to this chapter that includes a decoupling mechanism. “Cost-effective conservation and energy efficiency program” means a program approved by the Commission that is designed to decrease the average customer’s annual, weather-normalized consumption of energy, for gas and nongas elements combined, or avoid energy costs or consumption the customer may otherwise have incurred, and is determined by the Commission to be cost-effective if the net present value of the benefits exceeds the net present value of the costs at the portfolio level as determined by not less than any three of the following four tests: the Total Resource Cost Test, the Program Administrator Test (also referred to as the Utility Cost Test), the Participant Test, and the Ratepayer Impact Measure Test. Such determination shall include an analysis of all five tests, and a portfolio of programs shall be approved if the net present value of the benefits exceeds the net present value of the costs as determined by not less than any three of the four tests. Such determination shall also be made (i) with the assignment of administrative costs associated with the conservation and ratemaking efficiency plan to the portfolio as a whole and (ii) with the assignment of education and outreach costs associated with each program in a portfolio of programs to such program and not to individual measures within a program, when such administrative, education, or outreach costs are not otherwise directly assignable. Without limitation, rate designs or rate mechanisms, customer education, customer incentives, appliance rebates, and weatherization programs are examples of conservation and energy efficiency programs that the Commission may consider. Energy efficiency programs that provide measurable and verifiable energy savings to low-income customers or elderly customers may also be deemed cost effective. A cost-effective conservation and energy efficiency program shall not include a program designed to convert propane or heating oil customers to natural gas. “Decoupling mechanism” means a rate, tariff design or mechanism that decouples the recovery of a utility’s allowed distribution revenue from the level of consumption of natural gas by its customers, including (i) a mechanism that adjusts actual nongas distribution revenues per customer to allowed distribution revenues per customer, such as a sales adjustment clause, (ii) rate design changes that substantially align the percentage of fixed charge revenue recovery with the percentage of the utility’s fixed costs, such as straight fixed variable rates, provided such mechanism includes a substantial demand component based on a customer’s peak usage, or (iii) a combination of clauses (i) and (ii) that substantially decreases the relative amount of nongas distribution revenue affected by changes in per customer consumption of gas. “Fixed costs” means any and all of the utility’s nongas costs of service, together with an authorized return thereon, that are not associated with the cost of the natural gas commodity flowing through and measured by the customer’s meter. “Measure” means an individual item, service, offering, or rebate available to a customer of a natural gas utility as part of the utility’s conservation and ratemaking efficiency plan. “Natural gas utility” or “utility” means any investor-owned public service company engaged in the business of furnishing natural gas service to the public. “Portfolio” means the program or programs included in a natural gas utility’s conservation and ratemaking efficiency plan. “Program” means a group of one or more related measures for a customer class. “Revenue-neutral” means a change in a rate, tariff design or mechanism as a component of a conservation and ratemaking efficiency plan that does not shift annualized allowed distribution revenue between customer classes, and does not increase or decrease the utility’s average, weather-normalized nongas utility revenue per customer for any given rate class by more than 0.25 percent when compared to (i) the rate, tariff design or mechanism in effect at the time a conservation and ratemaking efficiency plan is filed pursuant to this chapter or (ii) the allocation of costs approved by the Commission in a rate case using the cost of service methodology set forth in § 56-235.2 or a performance-based regulation plan authorized by § 56-235.6, where a plan is filed in conjunction with such case.