Korea's top electricity provider, state-run Korea Electric Power Corp. (KEPCO), enjoyed a sharp improvement in its profitability last year with its margin from selling electricity bought from private firms hitting the highest since 2007, industry data showed on Monday.

According to the data, KEPCO sold one kilowatt-hour (kWh) of power at 111.57 won ($0.10) last year, slightly up from the previous year's 111.28 won. In contrast, private electricity firms sold electricity to KEPCO for 84.05 won per kWh last year, down 7.2 percent from 90.53 won.

The margin stood at roughly 25 percent, the highest since 2007 when the comparable figure was 27 percent, according to the data.

KEPCO's net profit soared to 13.41 trillion won last year from 2.7 trillion won the previous year, thanks to cheaper fuel costs and profit from its land sale.

Operating income jumped 96.1 percent to 11.34 trillion won over the cited period.

The large increase in KEPCO's earnings in 2015 came amid growing demand for a cut in electricity rates to reflect a plunge in global oil prices.

The additional net profit partly came from the sale of the company's Seoul headquarters to Hyundai Motor Group for 10.55 trillion won in late 2014, with the payment coming in last year.

Private utility firms such as POSCO Energy and GS EPS suffered a drop of up to 50 percent last year due to increased competition and a cut in prices of power sold to KEPCO.

There have been growing calls for a cut in electricity bills given low oil prices and a slump in Asia's fourth-largest economy. (Yonhap)