Privatised utilities are typically characterised by both undervaluation and underpricing. When faced with this problem, regulators have tended to employ a market-value approach to determine the regulatory asset base. This paper analyses this approach and shows that it magnifies the impact of any ‘short-lived’ error at privatisation and has the effect of entrenching relative errors forever. We then address the question whether there is an alternative mechanism that can accommodate the undervaluation problem but does not fall foul of the difficulties inherent in the market-value approach. The alternative we suggest is to use the regulatory agency's own estimate of the company's value, which we call the model-based asset value. It is shown that errors made at the time of privatisation do not have the same impact on future prices, and hence far less effect on the potential sale price.