Eight out of Japan's 10 regional utilities posted group net losses for the April-September period, reflecting surging fuel costs amid the continued shutdowns of their nuclear power plants, according to earnings reports released as of Wednesday.

The eight companies posted a combined net loss of ¥670 billion, flagging performances that could prompt many of them to hike power rates, after Tokyo Electric Power Co. did so in September.

The half-year net loss reached record highs at Kansai Electric Power Co., Kyushu Electric Power Co. and Hokkaido Electric Power Co., according to the reports. As the three utilities depend relatively highly on nuclear power, they were affected by the surge in alternative fuel costs for thermal power generation. Two of Kepco's reactors are the only ones out of the nation's 50 commercial units now operating.

The government is expected to demand further cost reductions from the utilities once they ask for permission to hike rates, which would deal a severe blow to households and businesses amid the protracted economic downturn, its officials said.

Shikoku Electric Power Co. President Akira Chiba said in an earnings report briefing Wednesday, "We want to decide soon" whether to raise power bills.

Kepco and Kyushu Electric have already announced they plan to hike rates.

Tepco raised rates for households by an average of 8.46 percent due to the meltdown crisis that started in 2011 at its Fukushima No. 1 nuclear plant.

Okinawa Electric Power Co., which does not have any reactors, and Hokuriku Electric Power Co., which does, did not incur a half-year loss.