The estimation of the cost of capital under CAPM for the purpose of setting regulated revenues is complex. To achieve an appropriate balance between stakeholders’ expectations and an efficient outcome, the regulator must exercise judgement.
Recognising that CAPM is just one approach to assessing the cost of equity and the weighted average cost of capital, the Tribunal uses it as a guide for ascertaining a “fair and reasonable rate of return” for a regulated business. To determine a single and ‘precise’ value for each of the input parameters is somewhat problematic. Careful consideration of the input
parameters will help establish a reasonable range for the cost of capital within the CAPM approach. The choice of a rate of return within this range is a matter of regulatory judgement. This judgement may be informed by the results of alternative models for assessing the cost of capital, assessment of risks specific to the utility, and evidence of market expectations.