How to Read a Korean Industrial Electricity Bill and Find the Leaks

If you run a tier-2 or tier-3 vendor plant supplying a semiconductor prime contractor, two pressures arrive at once these days. One is an electricity bill that keeps climbing; the other is the RE100 requests that have started coming down from the prime. And yet it is rare for anyone to read the monthly electricity bill properly from top to bottom. Almost every point where your plant wastes power is already recorded on that single sheet.

The four items to check on the bill

The bill looks crowded, but from a savings point of view there are four places you have to look.

1. Top — contract type and contract power

The top of the bill shows the contract type and the contract power (kW). These two are the starting point for the basic charge.

The contract type is one of Industrial (A), Industrial (B) or Industrial (C). Below 300 kW of contract power it is Industrial (A), from 300 kW it is Industrial (B), and at 1,000 kW or more on extra-high-voltage supply it is Industrial (C). Most tier-2 and tier-3 semiconductor vendors fall in the Industrial (B) band.

What to check here is whether the contract power matches how you actually run. More often than you would expect, a plant adds equipment or cuts a line and leaves the contract power untouched. If contract power is set more than 20% above your actual peak usage, you are paying a basic charge every month on capacity you never use.

2. Middle — find the maximum demand

Around the middle of the bill is the maximum demand (kW) used as the basis for the basic charge. This number matters because the basis is the power reading from the single highest moment in the past 12 months.

For semiconductor suppliers this often happens while responding to an urgent order from the prime. If the maximum demand shown on the bill is far out of line with the utilisation you sense day to day, do check 12 months of data to see when the peak occurred.

3. Middle — the energy charge by time band

The energy charge is shown split into three bands: off-peak (overnight), mid-peak and peak (the daytime peak). The unit-price gap between the bands is considerable. It varies by season and time band, but the peak unit price runs at two to three times the off-peak unit price.

Looking at the usage split across the three bands shows you your plant's operating pattern. If peak-band usage is more than 50% of the total, it is worth examining whether some processes can be moved into the overnight hours. There are supplier cases where moving relatively time-flexible processes such as precision cleaning, packing and inspection to night shifts cut the monthly electricity bill by 8 to 12%.

4. Bottom — the power factor charge: discount or surcharge?

If the power factor charge at the bottom of the bill is a plus (+), it is a surcharge; a minus (−) is a discount. During daytime hours (08:00–22:00), for every 1 percentage point below the 92% lagging power factor benchmark, an extra 0.2% of the basic charge is billed (KEPCO's Basic Terms of Supply, Article 43(2), in force 1 February 2025).

The widely repeated "90% benchmark" is the pre-amendment figure. The calculation is covered in detail in Power factor and the power factor charge.

Semiconductor supplier plants carry a lot of inductive load — large constant-temperature-and-humidity units, cleanroom air handling, compressors — which makes it easy for the power factor to fall.

At a power factor of 85%, (92 − 85) × 0.2 = 1.4% of the basic charge goes out extra every month. If the monthly basic charge is KRW 5 million, that is KRW 70,000 a month and KRW 840,000 a year lost to the power factor surcharge alone (an illustrative example based on assumptions). Install capacitors and lift the power factor above 92% and the surcharge disappears; up to 97% a reduction is applied.

But at night the trap runs the other way. Between 22:00 and 08:00 a separate 95% leading power factor benchmark applies, and on that side there is only a surcharge for falling short, with no reduction. Leave too much capacitance connected and the plant tips into leading at night, giving back at night what it saved during the day. When you add equipment, look at the night-time power factor too.

What a single bill can tell you

If the RE100 requests have already arrived

Understanding the structure of your electricity bill precisely goes beyond straightforward cost saving: it is the starting point for designing a renewable transition later. Semiconductor primes' RE100 requirements start with tier-1 suppliers and work down to tier-2 and tier-3 vendors in stages. If you cannot read the bill properly today, responding to RE100 is bound to feel impenetrable.