A record heat wave and sweltering temperatures even after sunset sent power consumption surging to the point where state-run utility KEPCO has gone into emergency mode. The Korea Power Exchange raised the power warning level to "caution" on Monday after the reserve electricity level or amount of available supply fell below 3 million kW.

The last time the KPX raised the power warning to "caution" was on Sept. 15 last year, when there was a massive blackout, with a reserve electricity level of 240,000 kW.

There are four levels -- attention, caution, alert and grave, depending on severity -- when the reserve falls below 4 million kW.

Power demand surged to a record 74.29 million kW at 3 p.m. on Monday, sending the reserve level to 2.79 million kW. The previous record in terms of power demand was 73.83 million kW on Feb. 2 this year.

Officials managed to decrease power consumption by around 1.3 million kW on Monday by urging businesses to conserve electricity in return for incentives. Without those efforts, the reserve level could have dropped as low as 1.49 million kW.

The main cause for the sharp decline in the reserve level is the heat wave gripping the nation. "We believe the cause is soaring temperatures which have remained above 33 degrees Celsius for more than a week," said Minister of Knowledge Economy Hong Seok-woo. "Power demand has gone beyond our estimates, since people leave their air conditioners on at night when they watch the London Olympics" due to the eight-hour time difference between the U.K. and Korea.

Each increase of one degree Celsius leads to an additional 600,000 kW of power demand, officials estimate.