How this calculator works
Not all the power a charger draws from the outlet reaches your battery — some is lost as heat during conversion, and DC fast chargers typically lose more than slow AC chargers. The energy you're billed for is higher than the energy your battery actually gains.
- capacity — battery capacity (kWh)
- efficiency — share of drawn energy that reaches the battery
Common values
| Battery capacity (kWh) | Charging cost |
|---|---|
| 6 kWh | ₩1,200 |
| 15 kWh | ₩3,000 |
| 30 kWh | ₩6,000 |
| 60 kWh | ₩12,000 |
| 90 kWh | ₩18,000 |
| 120 kWh | ₩24,000 |
| 180 kWh | ₩36,000 |
More detail
Why billed energy is higher than battery energy
A charger's AC-to-DC conversion and battery-management overhead both waste some energy as heat. A 90% efficiency means a 36 kWh top-up actually draws 40 kWh from the charger — the extra 4 kWh is what you pay for but never reaches the battery. Fast DC chargers tend to run a few points lower than slow home charging.
Rate tip. Home charging is usually billed at your household electricity rate, while public fast chargers charge a flat per-kWh price that's often several times higher. Compare both rates for the same trip before assuming home charging is always cheaper.
Frequently asked questions
Why is my charging bill higher than capacity × price would suggest?
Because of conversion losses. A 60 kWh battery charged from 20% to 80% adds 36 kWh, but at 90% efficiency the charger draws 40 kWh from the outlet — so the bill is based on 40 kWh, not 36.
How much does charging a 60 kWh battery from 20% to 80% cost at 300 won/kWh?
At 90% efficiency: 36 kWh reaches the battery, 40 kWh is drawn, costing 40 × 300 = 12,000 won.
Does charging efficiency matter more for fast or slow charging?
Fast DC charging generates more heat per minute, so its round-trip efficiency is usually lower than slow AC charging. Lower efficiency means more billed energy for the same amount added to the battery — enter your charger's actual efficiency above to see the difference.