An Auditor-General's report on risk management at Transpower says it is not clear how well the company is prioritising upgrades to the national electricity grid.
The report highlights Transpower's need for a modern asset management system, so it can prioritise replacement and refurbishment work.
Transpower chief executive Patrick Strange says work on a $20 million asset risk management plan is under way and should be completed by 2013.
He says being without the plan has not been an issue so far, because investment has been targeted at the areas of the grid that most obviously needed upgrading.
Dr Strange says however that such a plan will be essential as the upgrading work progresses.