The CEO of the World Green Organisation, William Yu, says he's expecting electricity tariffs to rise by at least 10 percent for CLP customers, and at least 30 percent for those with HK Electric.
The two power firms will on Tuesday announce their tariff arrangements for next year.
Yu told RTHK that the increases will be due to price fluctuations in the international energy market.
He said he thinks many people will have to think of ways to cut down on their electricity use, but also added that relatively cheaper natural gas is expected to be available after the completion of an LNG terminal next year.
"Theoretically speaking, it should be easier to find relatively cheaper liquefied natural gas after the terminal is completed. That will help cut fuel costs, and hopefully by then geopolitical tensions and oil prices will be less of a factor," he said.
Meanwhile, Kenny Ng from the Kwai Chung Subdivided Flats Residents Alliance said poorer people will bear the brunt no matter how much prices rise.
He said he hopes the two power firms can consider offering subdivided flat residents "very hot weather subsidies".