State-run utility firm Korea Electric Power Corp. has to repay or roll over some 10 trillion won ($9.1 billion) worth of debts which are due by 2018, industry data showed on Tuesday.

According to the data compiled by FnGuide, KEPCO's debt totaling 10.2 trillion won should be paid back or rolled over by 2018. It includes foreign currency-denominated debt, and is equivalent to some 40 percent of its outstanding corporate debts amounting to 26 trillion won in total.

This year alone, the electricity supplier has to repay or roll over 1 trillion won.

But KEPCO's interest payment for the year may top 1 trillion won as well, which translates into some 2 trillion won in cash needed for debt repayment and interest payment this year.

The data came as South Korea has been suffering from scorching heat for weeks, with Seoul's average daily high hovering around 33 C and its daily low remaining over 25 C last week, causing a surge in electricity consumption, which added to concerns among general households over what they call "electricity bill bombs."

As part of efforts to curtail electricity consumption, South Korea uses a "progressive" billing system for households. The system is not applied to industries that account for over half of the country's energy consumption.

Under the system first introduced during the oil crisis in the 1970s, a household pays 60.7 won per kilowatt for the first 100 kilowatts in a month. But the rate rises to 125.9 won if it consumes between 100 and 200 kilowatts.

The price even shoots up to 709.5 won per kilowatt -- nearly 12 times more than the basic price -- if they consume electricity in excess of 500 kilowatts each month.

KEPCO has been pressed to lower electricity rates amid the extended heat wave.

Last week, the government said it will work to cut electricity rates for private households amid mounting calls to overhaul the country's electricity billing system that critics say exceedingly overcharges users. (Yonhap)