The litre figure on a refrigerator spec sheet is not the size of the cabinet. It is the effective internal volume measured under KS C IEC 62552. And the energy efficiency grade printed beside it is not an absolute power figure — it is a score relative to that volume. Put those two facts together and a common showroom paradox resolves itself: a 299-litre Grade 1 unit draws 4.86 kWh less per month than a 253-litre Grade 2 unit.
Both figures come from the refrigerator efficiency filing database maintained by the Korea Energy Agency. Everything calculated below uses that public filing data and the published KEPCO tariff, nothing else.
What the litre number actually measures
The Ministry of Trade, Industry and Energy's Efficiency Management Equipment Regulation covers refrigerators with rated power of 500W or less and effective internal volume up to 1,000 litres. Effective internal volume is the space you can actually put food into: total drawn volume minus the rounded interior corners, the door-seal lip, and the clearance needed for cold air to circulate.
That is why two 800-litre units can have different cabinet widths, and why two cabinets of identical width can differ by tens of litres depending on door design. Four-door models lose more to the door structure than two-door models, and the measurement method is the reason.
Household-size rules of thumb sit on top of this. The common formula is 100 litres per person plus 50 to 100 litres of headroom, though Korean households storing kimchi and fermented pastes typically stretch the headroom to 100–150 litres. A family of four lands at 500–600 litres, or above 700 without a separate kimchi refrigerator (gimchi-naengjanggo, a dedicated fermentation fridge). Since these are labelled-volume figures, how usable the space feels still depends on the split between fridge and freezer compartments.
Why Grade 1 does not mean lower consumption
The grade is assigned from an efficiency indicator called R, not from consumption itself. As the HVAC trade publication kharn sets out, R is the ratio of a model's maximum permitted monthly consumption to its actual monthly consumption. For household refrigerators, R of 2.10 or above earns Grade 1, 1.85 to 2.10 earns Grade 2, and 1.60 to 1.85 earns Grade 3. Kimchi refrigerators face a stiffer Grade 1 threshold of 2.55.
The numerator — maximum permitted consumption — is derived from adjusted effective volume. Larger capacity raises the allowance. The grade is therefore a ranking within a capacity band, not a comparison across bands.
The measurement convention is worth noting too. The monthly consumption printed on the label is daily consumption multiplied by 365, divided by 12, then multiplied by 1.6. That 1.6 correction factor is already there to approximate real use — doors opening, warm food going in. Unlike a washing machine label, which is quoted per cycle, a refrigerator's label figure is close to what the appliance will actually add to the meter each month.
Pulling real models from the filing database and converting to consumption per 100 litres and annual cost shows what the grade label conceals.
| Model (maker) | Effective volume (L) | Monthly consumption (kWh/mo) | Grade | Per 100L monthly (kWh) | Annual cost (won) |
|---|---|---|---|---|---|
| HR130MLS1-D1TO (Deoham) | 126.4 | 23.21 | 3 | 18.4 | 71,860 |
| KRNT255SEM3 (CRK) | 255.0 | 20.93 | 1 | 8.2 | 64,800 |
| R262GW1-D2BM (Deoham) | 253.5 | 33.09 | 2 | 13.1 | 102,450 |
| QRBA30US5MF (QAid) | 299.0 | 28.23 | 1 | 9.4 | 87,400 |
| HH312RS (Elechome) | 312.0 | 26.07 | 1 | 8.4 | 80,710 |
| CRG-CR4830MEW (Cuckoo) | 478.5 | 36.88 | 3 | 7.7 | 114,180 |
Annual cost multiplies monthly consumption by 12 and applies 258 won per kWh. That rate builds on the second-tier energy charge of 214.6 won in the KEPCO residential low-voltage tariff, plus 14 won of climate-environment and fuel-cost adjustment charges, then 10% VAT and a 2.7% power industry fund levy. Households under 200 kWh a month pay 151 won at the margin; above 400 kWh it becomes 362 won.
The last row is the striking one. The 478.5-litre Grade 3 unit is the most efficient in the table per 100 litres at 7.7 kWh, yet it carries the lowest grade. The 126.4-litre Grade 3 unit is more than twice as wasteful per litre at 18.4 kWh, but its small body keeps annual cost more than 40,000 won lower. Grade and running cost are measuring different things.
The efficiency grade is a league table among appliances of the same size. The bill is size multiplied by rank.
What extra capacity actually costs
Start with the effect of moving up a grade within one size band. The 255-litre Grade 1 and the 253.5-litre Grade 2 differ by 12.16 kWh a month — 145.9 kWh a year, or 37,650 won. Two refrigerators of essentially identical size, one grade apart, separated by 370,000 won over a decade.
Going bigger costs less than expected. The 299-litre Grade 1 is 45 litres larger than the 253.5-litre Grade 2 and still uses 4.86 kWh less per month, saving 15,050 won a year. Against the 312-litre Grade 1, the gap is 58.5 litres larger and 21,740 won a year cheaper.
The 478.5-litre Grade 3 changes the picture. It is 166.5 litres larger than the 312-litre Grade 1 and costs 33,470 won more per year. Most efficient per litre, but firmly in the territory where absolute consumption climbs. One rule falls out of this: raising capacity while also raising the grade barely moves the bill and can reduce it; raising capacity while dropping the grade raises it immediately.
Progressive tariff tiers deserve one more line. A refrigerator runs continuously, so its consumption sits underneath everything else in the house. A household already at 380 kWh a month that swaps a 30 kWh unit for a 40 kWh one pushes much of that extra 10 kWh past the 400 kWh boundary into the 362-won tier — 2.4 times what the same 10 kWh would cost a household still inside the first tier.
The order to decide in, and when to wait
Judging from published specifications alone, the sequence runs like this. Measure the width, depth and door swing of the installation alcove first; that sets a physical ceiling. Within that ceiling, size the effective volume by household count, subtracting 100–150 litres if a separate kimchi refrigerator already handles that load. Once the shortlist is narrow, compare the labelled monthly consumption. Grades are a valid comparison only when the candidates share a capacity band.
Who this suits. Households of four or more, those who shop in bulk, or anyone trying to cover everything with a single unit will do better hunting for Grade 1 above 500 litres. The one-grade gap that produces roughly 370,000 won over ten years applies directly.
When to wait. If the current refrigerator is a 300-litre-class Grade 1 showing no signs of failure, replacing it purely for more space will not pay back. On the table's figures, moving from a 312-litre Grade 1 to a 478.5-litre Grade 3 adds 33,470 won a year, so savings cannot be the justification. And where the alcove width is marginal enough to need built-in dimensions checked, buying the appliance before measuring the space is the wrong order.