Units · 5 min read
kW vs kWh, explained
One is the size of the tank, the other is the size of the hose.
Two units show up on every EV spec sheet and they're easy to mix up. One is an amount of energy. The other is how fast energy moves.
kWh · kilowatt-hour
The size of the tank
Energy stored. A 75 kWh battery holds 75 kWh. More kWh means more range.
kW · kilowatt
The size of the hose
Power, the rate energy flows. A 150 kW charger can push up to 150 kWh in one hour.
Charging time is just division
To add 45 kWh on a 7.7 kW home charger: 45 ÷ 7.7 ≈ 5.8 hours, plus about 10% for losses, so a bit over six hours.
The slower side always wins
The power you actually get is the lower of what the charger offers and what the car accepts. A car that tops out at 50 kW charges at 50 kW on a 350 kW charger. A car that accepts 11 kW on AC gets 7.7 kW from a 7.7 kW wall box.
Fast charging slows down as it fills
On DC fast chargers the car pulls near its peak only when the battery is fairly empty, then tapers to protect the cells. That's why fast-charge times are quoted from 10% to 80%. Past 80% it can take as long to add the last 20% as it took to add the first 70%.
Our model-page estimates assume an average of about 60% of the advertised peak between 10% and 80%. Real sessions vary with battery temperature and the station.
Next up: which charging level you actually need.