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.