(1)(a) Each utility must incorporate the social cost of greenhouse gas emissions as a cost adder for all relevant inputs when evaluating and selecting conservation policies, programs, and targets; developing integrated resource plans and clean energy action plans; and evaluating and selecting intermediate term and long-term resource options.

(b) The greenhouse gas emissions cost adder may be adjusted to account for any explicit tax or fee on greenhouse gas emissions that is known or assumed in the resource analysis.

(2) A utility may comply with the requirements of subsection (1) of this section by using one of the following analytical approaches, as appropriate and consistent with the utility's overall analytical approach for resource planning, evaluation, and selection:

(a) Performing a resource analysis in which it increases the input cost of each fossil fuel by an amount equal to the social cost of greenhouse gas emissions value of that fuel;

(b) Conducting a resource analysis in which alternative resource portfolios are compared across multiple scenarios on the basis of cost, risk, and other relevant factors and the aggregate social cost of greenhouse gas emissions is added to the cost of each resource portfolio;

(c) If the utility does not use a comprehensive resource portfolio evaluation and optimization approach: Adding the social cost of greenhouse gas emissions to the expected market price of electricity, using an estimate of the emissions rate of marginal generating resources; or

(d) Using another analytical approach that includes a comprehensive accounting of the difference in greenhouse gas emissions and social cost of greenhouse gas emissions between resource alternatives.

(3) Any methodology used to comply with this rule may assume that the social cost of greenhouse gas emissions cost adder does not affect short-term operations or dispatch decisions after energy resources are acquired and placed into service.

(4) Any methodology used to comply with this rule must ensure that the social cost of greenhouse gas emissions cost adder is accounted for without unreasonable duplication or double counting.

(5) The social cost of greenhouse gas emissions values used to meet the requirements of this chapter are specified in WAC 194-40-100.