In the context of decision support, the Technology Assessment (TA) group makes use of two aggregation approaches in order to consider all possible criteria (e.g., environmental, economic and social for sustainability assessment). The two approaches are the estimation of total costs (TC) and Multi-Criteria Decision Analysis (MCDA).
Total costs represent the sum of the internal (or production) and external costs both for individual energy technologies (i.e., electricity, heating and cooling, mobility) and at the scenario level. They are sometimes also used as a measure of sustainability, although this is controversial because the social dimension is only partially taken into account. Costs are called “external” if they are not born by the party that causes them, but rather by society as a whole, i.e., the costs of health damages that result from air pollution, the costs of accidents, etc. External costs are monetized, or valued in monetary units, using several methods, including damage costs, avoidance costs (e.g., to reduce emissions), or people’s willingness to pay. Total costs cannot be considered objective as valuations are uncertain, stakeholders do not generally agree on them, and there is no actual market where values are established and paid. Some aspects of social acceptance such as perceived risks or visual amenity are strongly subjective and may be very difficult to monetize. Therefore, non-monetized factors are not considered in the final total cost estimates.
On the other hand, MCDA has the capability to explicitly reflect subjective social acceptance issues. Generally, it compares selected alternatives based on a given set of criteria and indicators using preferences elicited from different stakeholders. In contrast to the total cost approach, MCDA does not just produce a single ranking of alternatives (e.g., technologies, scenarios), but rather is suitable for different problem typologies (e.g., ranking, sorting, choice) and aims to address conflicting objectives and to systematically explore potential trade-offs and co-benefits to identify robust and widely accepted solutions. The MCDA process can be divided in several distinct steps. First, the alternatives to be compared must be defined. Second, indicators are established for the criteria of interest (e.g., environmental, economic and social). Third, indicators need to be established for all alternatives. Fourth, depending on the problem of interest, a suitable MCDA method must be selected (e.g., for ranking, sorting, etc.). Fifth, stakeholder preferences are elicited, for example how much importance is assigned to each individual indicator in a weighting scheme. Finally, based on the selected MCDA method the final outcome is given in terms of scoring, ranking, class of preference, etc., which is then used to support the decision-making process. Stakeholder or decisionmaker inputs and/or feedback are preferably solicited at each step of this process (not just preference elicitation) to build confidence and acceptance of the MCDA results. MCDA does not provide a single, definitive ranking or scoring of alternatives, but rather illustrates the sensitivity of the ranking to the subjective preferences provided by the various individual or group stakeholders. Often presentation of the MCDA results can result in iterative adjustment of stakeholder preferences. Overall, the MCDA approach enables one to account for a wide variety of aspects in a transparent and consistent manner. It can provide an invaluable support to informed decision-making, and in guiding public debate and participative processes.