A Korean city gas bill prints a volume — "100 m³" and so on. But the charge is not set on that volume. Since July 2012 city gas has been billed on heat, in megajoules. That is why the same 100 m³ costs a different amount in different months.
1. A heat value sits in between. 100 m³ × 43.0 MJ/m³ = 4,300 MJ, and the unit price applies to that.
2. There is no single national rate. The wholesale half is approved by the Minister, the retail half by the province.
3. The discount is a cap, not an amount. Table 1 of the notice sets limits; the amount itself is set by the suppliers.
4. Taking the energy voucher lowers the winter cap by 62,000 won — and the whole reduction comes off the wholesale side.
Put the numbers from your own bill in and it shows where each piece is added and cut.
It follows the order the bill is built in. Korean city gas has been charged on heat since July 2012: the volume in cubic metres is multiplied by that month's heat value (MJ/m³) to give the heat used, and that by the unit price (won/MJ) to give the usage charge. The price is the wholesale rate plus the retail supplier's cost, and the wholesale half is approved by the Minister while the retail half is approved by the province (Enforcement Decree Rule art. 34-2 of the City Gas Business Act). So the unit price and standing charge differ by supplier — the defaults here are Seoul City Gas, Seoul area, residential, effective 1 September 2026. The discount is the cap in table 1 of the Regulation on Calculating City Gas Discount Support Limits (notice 2025-24), applies to the usage charge with the standing charge excluded (art. 2(2)), and is prorated by day from the day after application (art. 6(1)). Article 10(2) says only that "the amount with the discount deducted shall be billed", so here the discount is taken before VAT — the order may differ by supplier. Proration, centrally heated apartment blocks, welfare facilities and special disaster areas are not included. An estimate — confirm against your bill.
The cubic metre is not the billing unit
Seoul City Gas explains it plainly: from July 2012 the tariff changed from a volume unit to a heat unit, and the heat value used is the one measured by heat meters installed at around a hundred supply points nationwide by the Korea Gas Corporation, so no household needs a meter of its own.
Carried through on the Seoul residential rate: 100 m³ × 43.0 gives 4,300 MJ, times 22.5268 won/MJ gives a usage charge of 96,865 won, and adding the 1,250 won standing charge and 9,812 won of VAT gives 107,927 won billed.
Which means the heat value differs by month and by supply point. It is printed on the bill, and the calculator is only right if you use that number. The 43.0 here is a placeholder.
There is no single national rate
KOGAS sets the wholesale rate; the retail supplier adds its own supply cost. The wholesale half is approved by the Minister of Trade and Industry, the retail half by the provincial governor (Enforcement Rule art. 34-2(2) and (3) of the City Gas Business Act).
| Layer | won/MJ | Who sets it |
|---|---|---|
| Feedstock cost | 17.712 | KOGAS, approved by the Minister |
| KOGAS supply cost | 3.1375 | same |
| = wholesale rate | 20.8495 | residential, 1 Sep 2026 |
| Retailer supply cost | 1.6773 | approved by the province - found by subtraction |
| = retail rate | 22.5268 | Seoul City Gas, Seoul area, residential |
| VAT excluded. The retailer supply cost of 1.6773 appears in no published table in that form — it is the retail rate minus the wholesale rate. Outside Seoul this line changes, which is why the calculator lets you overwrite the unit price. | ||
In the increase effective 1 September 2026, residential cooking and heating alone was held at 0.0%. On the same table, commercial heating rose 5.7%, industrial 6.3% and transport 6.4%.
The voucher lowers the winter cap by 62,000 won
On 1 December 2025 the Regulation on Calculating City Gas Discount Support Limits (notice 2025-24) came into force as a new instrument. The leftmost column of its table 1 splits everyone into those who do not receive the energy voucher and those who do.
For winter (December to March) cooking and heating, a household on the livelihood or medical benefit has a cap of 148,000 won, and 86,000 won if it also holds the energy voucher. 62,000 won comes off, and all of it from the wholesale side — the retail share of 7,200 won is identical on both rows.
Over four winter months that is 248,000 won. And the winter portion of the energy voucher for a one-person household is 254,500 won — a difference of 6,500 won.
Whether the two were designed to offset each other the notice does not say. The numbers simply sit that way. With two or more people the voucher is larger, so the offset is close only for a single-person household.
The benefit type does not change the total: all four caps are 148,000 won. What differs is only the retail share — 7,200 won for livelihood and medical, 3,600 won for housing and near-poverty, 1,800 won for education. The wholesale side absorbs the difference.
| Category | Winter Dec-Mar | Rest Apr-Nov | Cooking only |
|---|---|---|---|
| livelihood / medical | 148,000 | 9,900 | 1,680 |
| housing benefit | 148,000 | 4,950 | 840 |
| education benefit | 148,000 | 2,470 | 420 |
| near-poverty | 148,000 | 4,950 | 840 |
| livelihood / medical (voucher) | 86,000 | 9,900 | 1,680 |
| housing benefit (voucher) | 86,000 | 4,950 | 840 |
| education benefit (voucher) | 86,000 | 2,470 | 420 |
| near-poverty (voucher) | 86,000 | 4,950 | 840 |
| severe disability | 72,000 | 9,900 | 1,680 |
| state merit | 72,000 | 9,900 | 1,680 |
| independence merit | 72,000 | 9,900 | 1,680 |
| near-poverty certificate | 18,000 | 2,470 | 420 |
| family with many children | 18,000 | 2,470 | 420 |
| Won per month. Cooking-and-heating figures; the cooking-only cap has no seasonal split. Table 1 of notice 2025-24 [28 November 2025]. These are caps, not amounts — Enforcement Rule art. 34-2(1) says the discount amount is set by the wholesale and retail suppliers. | |||
Almost all of it sits in four winter months
148,000 won in winter, 9,900 won the rest of the year, 1,680 won for cooking only. That is 15 times and 88 times. A household that does not heat with gas gets a cap of 1,680 won a month.
And the cap is not handed over a month at a time. Article 6(1) says the discount applies from the day after the application and the cap is calculated by day, in proportion to the days it applies. Apply in mid-December and that month's cap is about half.
Questions that remain
Is the standing charge discounted too?
No. Article 2(2) applies the discount to the usage charge with the standing charge excluded. So even in a month with almost no gas used, the 1,250 won standing charge and its VAT remain.
Do I have to report starting the voucher?
Yes. Article 7 lists whether you qualify for the energy voucher among the changes that must be reported, and states that no retroactive application is possible for the period between the change and the filing.
Who pays for the discount?
Enforcement Rule art. 34-2(2) and (3) answer it: the wholesale discount is reflected in the wholesale supply cost and the retail discount in the retail supply cost. That is why table 1 bothers to split every figure into total, wholesale and retail.
What if there is no separate meter?
Article 2(1) requires the recipient's meter to be installed separately from other users' meters. In a centrally heated apartment block without separation, the estate's cap is apportioned by the ratio of eligible households to total households (same paragraph, subparagraph 2).
What does this calculator leave out?
Proration by day, the apportionment in centrally heated blocks, welfare facilities (calculated from a unit-price difference), special disaster areas (table 2), the settlement and clawback provisions, and whether VAT is charged before or after the discount. The notice says only that "the amount with the discount deducted shall be billed", so here the discount is taken first.
Sources
Enforcement Rule of the City Gas Business Act [in force 31 March 2026] [Rule 10] — article 34-2 (discount support amount). The amount is set by the wholesale and retail suppliers, and each half is reflected in the corresponding supply cost.
Regulation on Calculating City Gas Discount Support Limits [in force 1 December 2025] [notice 2025-24, newly established] — article 2 (the caps, standing charge excluded), article 6 (from the next day, prorated), article 7 (reporting changes), article 10 (billing net of the discount), table 1 (the caps).
Rates come from the Korea Gas Corporation's wholesale rate table for city gas (as of 1 September 2026) and Seoul City Gas's rate table for the Seoul area (effective 1 September 2026); the standing charge and the account of heat-unit billing are from the same company's rate and heat-value pages.
The script was checked against the model across 7,200 combinations, in Korean and in English — 5 volumes x 3 heat values x 3 unit prices x 2 standing charges x 2 seasons x 2 uses x 10 categories x voucher 2, with no mismatch. That check turned up a place where showing the heat used to one decimal made Python and JavaScript round differently, so it is now an integer.
Where to check
Winter support is best read alongside the energy voucher calculator — each one cuts the other. Electricity sits in the electricity bill calculator, and the cooling side in what one degree of air conditioning costs.
