The weighted average cost of capital (WACC), in relation to a covered electricity network, means a weighted average of the cost of debt and the cost of equity. The WACC is expressed as a percentage and is calculated under section 6.64 of the Electricity Networks Access Code (Access Code). Under the Access Code an access arrangement must set out the WACC for a covered network. The Access Code allows the ERA to make and publish a determination of the preferred methodology for calculating the WACC in access arrangements.

The Economic Regulation Authority (ERA) issued a notice confirming the expiration of the preferred WACC methodology on 22 April 2010.
On 25 February 2005, the ERA published a notice with respect to a determination on the preferred WACC methodology to apply to electricity networks that are covered under the Access Code. The preferred WACC methodology was published under section 6.65 of the Access Code and had effect for five years, commencing 25 February 2005.