EV Charging Efficiency Calculator
The electricity at your wall isn't all going into the battery. See how much is lost in AC and DC charging — and the real cost of that wasted energy.
Charging loss
Energy at the wall
Real cost / 100 km
Loss cost / year
Efficiency comparison
| Charging method | Efficiency | Loss | Real cost/100 km |
|---|---|---|---|
| DC fast charging | ~94% | 6% | |
| AC home (mild) | ~90% | 10% | |
| AC home (winter) | ~85% | 15% |
Frequently asked questions
How much energy is lost when charging an EV?
AC charging loses roughly 8-15% of energy in the conversion, while DC fast charging loses 5-8%. Cold batteries and high charge rates increase losses to 15-20%.
Why does my EV use more electricity than expected?
Charging losses, battery conditioning, cabin heating and vampire drain all add up. It's normal to see 15-20% more electricity consumed at the wall than the battery actually stores.
Does charging at 100% reduce efficiency?
Yes — the 80-100% charge segment is slower and less efficient due to battery management. Charging to 80% regularly avoids this wasted energy.
How can I reduce charging losses?
Charge at moderate power (7-11 kW), avoid extreme cold, charge soon after driving while the battery is warm, and keep the battery between 20-80%.