Industrial (A) or Industrial (B): One Line on the Bill Changes the Arithmetic

The Industrial (A) or Industrial (B) written in the "contract type" box at the top of your bill is not a mere classification label. That one line decides, all at once, your basic charge unit price, your energy charge unit price, whether time-of-use rates apply, and even whether you are covered by the recent tariff reform.

What is the difference between Industrial (A) and (B)?

The scale of contract power differs, and because of that the whole tariff table that applies is different. (A) and (B) are both industrial, but the basic charge unit price and the energy charge unit price are published separately for each.

Source: Basic Terms of Supply, Article 59(2) (in force 2026.07.01).

One exception is missing from the table. Even where contract power is 300 kW or more but under 500 kW, if you are supplied at low voltage, Industrial (A) low-voltage power applies (Basic Terms of Supply, Article 59(3)). That is because (B) has no low-voltage category at all. Look only at contract power and conclude "we are over 300 kW so we are (B)", and you will be wrong in this bracket. You have to check the supply voltage as well.

There is one more thing to watch. The 300 kW boundary is the threshold for the industrial class, not for every use class. For the educational class, for example, (A) is 4 kW or more and under 1,000 kW, and (B) is 1,000 kW or more (Basic Terms of Supply, Article 58(2)). Memorise "(A) and (B) split at 300 kW" and you will be wrong in other use classes.

How is the contract power that divides (A) from (B) determined?

It is determined by equipment capacity, not by actual consumption. Article 20 of the Basic Terms of Supply provides that contract power is calculated by multiplying the sum of the individual inputs of the consuming equipment by conversion rates.

Source: Basic Terms of Supply, Article 20(1)1 (in force 2026.07.01).

That means the total of all your equipment is not itself your contract power. For a factory whose equipment totals 300 kW, the converted result is 75×1.0 + 75×0.85 + 75×0.75 + 75×0.65 = 243.75 kW, and because the note to that same provision requires fractions below 1 kW to be rounded at the first decimal place, the contract power comes out at 244 kW. It is 300 kW on an equipment basis but stays in (A) on a contract power basis. Where the contract is based on transformer capacity, the sum of the rated capacities of the primary transformers is used, and 1 kVA is treated as 1 kW here. A fuller account of the calculation is in What contract power is.

Why are (A) I and (A) II separated?

It is not contract power but supply voltage that divides them. Article 59(5) of the Basic Terms of Supply provides that Industrial (A) customers on high voltage are subject to Industrial Power (A) II in Appendix 1 (the monthly electricity tariff table). (A) II has no low-voltage column, and low-voltage customers are subject to (A) I low-voltage power, so the result is that (A) I is low voltage and (A) II is high voltage.

The "kW boundary that divides (A) I from (A) II" that people often look for does not exist in the terms of supply. Where a high-voltage customer is metered at low voltage, the charge treatment is set separately in the Implementation Rules (the proviso to the same paragraph).

What that split leads to is whether you are metered by time of day. Article 38(2) of the Basic Terms of Supply provides that time-of-use meters are to be installed for General (A) II, Industrial (A) II, General (B), Educational (B), and Industrial (B). In other words, time-of-use (TOU) rates start from (A) II, and (A) I has no time-of-day distinction.

This means the very way you reduce your bill is different. (A) II and (B) can cut the energy charge by moving operations across off-peak, mid-peak, and peak, whereas (A) I has no such lever at all. Moving up from low voltage to high voltage does not just mean a different unit price table; it also means you gain a new means of cutting your bill by shifting the hours you operate.

Is (B) always cheaper?

No. (A) and (B) simply have different unit price tables; neither is structured to be unconditionally favourable. As contract power grows, the total basic charge grows with it, so a lower unit price is no guarantee of a lower total.

And in the first place, (A) and (B) are not something you choose. The structure is that when contract power crosses the boundary, the class follows it across. What actually determines your position is not whether you are (A) or (B) but the optional tariff you choose within the same class, and how you manage maximum demand.

Did the April 2026 tariff reform apply to (A) as well?

The unit price changes applied to Industrial (B) only. In the tariff table in force 16 April 2026, what changed in price was Industrial (B); the unit prices for Industrial (A) I and II, for General, and for the low-voltage classes have not changed since 1 April 2025. The basic charge unit prices did not change either.

The redrawing of the time bands took effect on different dates for different classes. It was not implemented on a single date across the board.

Source: Basic Terms of Supply, supplementary provisions (2026.3.16), transitional measures items 2 and 5 (in force 2026.07.01).

It is not that "everything else" was pushed back to 1 June. Appendix 3 (the table of seasonal and time-of-day divisions) applies only to classes metered by time of day, so low-voltage, non-time-of-use classes including Industrial (A) I were never covered by the redrawing in the first place.

As a result, between 16 April and 31 May 2026 the time bands differed from one class to another even within the same month. For what the reform contains, see The time-of-use tariff reform explained.

On top of this there is a grace period that applies to Industrial (B) alone. Item 4 of the transitional measures in the same supplementary provisions defers application of the revised Appendices 1 and 3 until 30 September 2026 for Industrial (B) customers who completed a grace period application during the period KEPCO announced. During the grace period, the former time bands continue to apply, but the energy charge is calculated with the adjustments below.

You have to establish whether your site applied for the grace period before you can read bills for April onwards properly.

Can we choose and change our contract type ourselves?

You do not choose the contract type itself; change your contract power and the class follows. Industrial (A) and (B) are values determined by your industry and your contract power, not items you apply for.

What we can actually move is contract power. If you have rationalised equipment or cut production lines so that contract power has become excessive, you can consider reducing it. The procedure and the constraints are set out in How to change (reduce) contract power. Note, though, that lowering contract power also lowers the floor used in calculating the basic charge, so you should move only after checking at least 12 months of records.

How do we check which one our factory is?

Looking at the "contract type" box on the bill is the quickest and most accurate way. Rather than calculating contract power and inferring it, read the value KEPCO has written on the bill as it stands.

There really are cases where the calculated value and the bill do not agree. Among the sites we manage there was one whose contract power was 350 kW but which was billed under the contract type Industrial (A) II (our own observation, 2026). The kW brackets in the tariff table are the basic criterion dividing the contract types, but the class an individual site is billed under can differ according to its contract history. The basis for a judgement is always the bill.