A verdict on Eskom's requested 53percent tariff increase will be given on June 6, the National Energy Regulator of South Africa said yesterday.
Eskom lodged its application with the regulator yesterday, requesting that the details not be made public because it included "sensitive business information".
Trade union Solidarity accused Eskom of a lack of transparency.
Solidarity last week lodged an application in terms of the Promotion of Access to Information Act (2 of 2000) for the disclosure of the confidential report.
The application was rejected after Eskom argued that the report will be published on the Nersa website today.
Solidarity spokesman Jaco Kleynhans said: "If the full report is not published, we shall ask for reasons before weighing further legal remedies.
"Solidarity will pursue its application in terms of the relevant legislation if the full report is not disclosed.
"Eskom's lack of transparency is clear from its request, but the public is entitled to the full motivation for the high increase."
Last week Solidarity appointed a team of forensic accountants to audit the Eskom application, including its motivation.
The full report will be published in early May.
Members of the public have until the end of April to take part in the public process and to submit input regarding the proposed increase. Solidarity will also submit its written commentary before the deadline.
The Democratic Alliance yesterday called for Eskom's status as the country's sole buyer of electricity to be revoked to encourage independent power producers.
The party also proposed that Eskom's transmission of electricity be unbundled from its generating division and transformed into a separate state-owned company, said spokesman on minerals and energy Hendrik Schmidt.
"A prohibitive regulatory environment continues to keep independent power producers at bay, and will continue to do so unless steps are taken to dismantle Eskom's monopoly and ensure private sector participation," Schmidt said.