Compare Water Dispenser Efficiency Grades Together with Tank Capacity

Are there cases in the same list where energy use and grade diverge?

Yes. Six models were copied from the agency detail pages on October 17, 2026. The list has 811 entries in total.

Based on the Korea Energy Agency efficiency grade product search detail pages.

CP-AE502, with the lowest energy use (18.55kWh/month), is grade 3, and IWP-3100N, with the highest (68.74kWh/month), is grade 2. Set the tank capacities beside them and IWP-3100N has 7.3ℓ cold and 8.2ℓ hot tanks, while CP-AE502 has 1.08ℓ and 1.12ℓ. For all six models, the grade followed the grading index order rather than monthly energy consumption.

What does the grading index reflect?

The agency page shows no formula. From the table alone, a lower index came with a lower grade number (0.61 is grade 1, 1.93 is grade 5), and the three models with large tanks (5.94 to 7.99ℓ cold tanks) all had lower indexes than the three with small tanks. How the index accounts for tank capacity cannot be stated from the pages checked, so this article goes only as far as saying to look at tank capacity alongside it.

Grade boundaries are not shown in the list either. As with 0.85 (WP-80S9P520M) and 1.01 (IWP-3100N) both being grade 2, index gaps remain within the same grade.

Which number matters more for my home?

It depends on how much you use. If one or two people draw small amounts, the monthly energy consumption of a small-tank model is the closer number for gauging household electricity use. If your household draws a lot at once, comparing grade and index among candidates with similar tank capacity is the better fit.

Either way, monthly energy consumption comes from the filing test. Actual energy use changes with how often you draw water and how much hot water you use, and the annual energy cost on the detail pages (the estimated amounts for CHPI-5820L and CP-AE502) has no calculation conditions on the same page, so do not use it as a bill estimate.

How do I match the model on a sales page?

1. Enter the full model name from the sales page or product label into the agency electric water dispenser list. Similar names such as CP-AE502 and CP-AE502HW are listed separately.
2. On each detail page, write the cold and hot tank capacities, monthly energy consumption, and grading index on one line per candidate.
3. Compare grade and index among candidates with similar tank capacity.

The top of the agency list notes that grade and efficiency can differ by manufacturing date and that the actual label may show a lower efficiency than the reported value. The basics of reading monthly energy consumption are the same as in reading monthly energy consumption on a refrigerator label. Finally, check once more that the monthly energy consumption on the store product's label matches the detail page value.