How to avoid a sky-high electricity bill during the heat wave

An electricity meter installed on a building in Seoul. [Yonhap]

As a record-breaking heat wave drags on and air conditioner use surges, electricity bills are becoming an increasingly heavy burden for households across the country.

In practice, an average four-person household running its air conditioner at a typical summer level can expect a monthly electricity bill of around 100,000 won ($70). If consumption exceeds 1,000 kWh, a "super-user tariff" kicks in and the bill can climb past 290,000 won.

According to Korea Electric Power Corporation, an average four-person household using its air conditioner at a typical level sees its monthly bill rise from 52,840 won in spring to 95,060 won in summer. With this year's intense heat driving up power consumption, bills are likely to exceed 100,000 won.

The key is staying below 450 kWh a month — the threshold where costs jump sharply. The single most important factor in determining an electricity bill is not how long the air conditioner runs, but which progressive pricing tier the household's total monthly consumption falls into.

Residential electricity rates operate on a three-tier progressive system. In tier 1 (up to 200 kWh per month), the energy charge is 120.0 won per kWh and the base fee is 910 won. Tier 2 (201–400 kWh) carries an energy charge of 214.6 won per kWh and a base fee of 1,600 won, while tier 3 (above 400 kWh) applies an energy charge of 307.3 won per kWh and a base fee of 7,300 won.

During July and August — when cooling demand peaks — the tier boundaries are temporarily relaxed to ease the burden on households. Under the summer adjustment, tier 2 applies from 301 to 450 kWh, and tier 3 kicks in above 450 kWh. Moving from tier 1 to tier 2 adds 94.6 won per kWh to the energy charge and raises the base fee by 690 won.

Once monthly usage crosses 450 kWh and enters tier 3, the energy charge rises by an additional 92.3 won per kWh and the base fee jumps by 5,700 won, causing costs to escalate sharply.

A household using exactly 450 kWh — the tier 2 ceiling — pays 85,740 won. But if consumption rises just 10 percent to 495 kWh, the bill climbs to 108,460 won, an increase of about 26 percent.

To help households avoid sudden bill spikes driven by surging cooling demand, Korea Electric Power Corporation has launched a real-time alert service that notifies customers when their electricity usage reaches 80 percent of the threshold for entering tier 3.

Alerts are sent through the KepcoON app or KakaoTalk. The utility is running the service as a pilot for about 2.3 million households enrolled in KepcoON, with plans to expand it to all approximately 11 million residential customers equipped with advanced metering infrastructure in December.

Using air conditioners efficiently is also important for keeping electricity bills in check.

Inverter-type air conditioners automatically adjust the outdoor unit's output once the target temperature is reached. Setting a consistent target temperature and running the unit continuously tends to use less power than repeatedly switching it on and off.

An experiment by researchers from Samsung Electronics' home appliance division, presented at the Korean Society of Mechanical Engineers' summer academic conference, found that turning an air conditioner off for 30 minutes and then restarting it consumed 5 percent more electricity than leaving it running continuously. Even a 60-minute absence resulted in 2 percent more consumption.

Once the absence exceeded 90 minutes, however, turning the unit off and back on used less electricity overall. An inverter air conditioner that has reached its set temperature maintains that temperature at low output, but switching it off briefly forces it to work hard to cool the room back down, consuming significantly more power in the process.

As a general rule, leaving an inverter air conditioner running during absences of less than 90 minutes — and turning it off for longer ones — can help reduce power consumption.

Fixed-speed air conditioners, by contrast, consume more power each time the outdoor unit cycles on and off. Rather than leaving them running for extended periods, it is more energy-efficient to turn them off once the room has cooled sufficiently and restart them after a set interval.

"Using a fan alongside the air conditioner helps circulate cool air more quickly, improving cooling efficiency, and blocking direct sunlight with curtains or blinds can slow the rise in indoor temperature," a Korea Electric Power Corporation official said. "Because air conditioners differ in how their outdoor units operate — fixed-speed versus inverter — it is important to use each type in the way that suits its characteristics."

oskymoon@heraldcorp.com