Environment minister Tse Chin-wan on Friday said changes should be made to a scheme under which the city's two power companies are rewarded with an additional return if they manage to resume electricity supply within a certain time frame after a blackout.

He also said the government is dissatisfied with Hongkong Electric over an error that caused a power outage in parts of Hong Kong for less than an hour in the early hours of Wednesday.

The firm explained on Thursday that the blackout was caused by a short circuit after its staff had accidentally connected an unrecorded backup cable to the power system.

Under a control agreement with the government, the power companies could receive financial incentives and penalties in respect of their performance in areas such as supply reliability and restoration.

For Hongkong Electric, there will be a 0.015 percent incentive adjustment if power is restored within 65 minutes on average.

"Given this incident, we believe that mechanism has room to improve. Therefore, taking the opportunity of the coming mid-term review of the agreement, the government will discuss with the two power companies on how to further improve the mechanism," Tse said.

The secretary for environment and ecology also said he believes Hongkong Electric would consider the government's suggestion to give back to the public if it receives an additional return over Wednesday's blackout.

The firm has not said if or how affected customers will be compensated.