How EV Charging Speeds (kW) Actually Work

EV charging is full of numbers — 7 kW, 150 kW, 80 kWh — and they're easy to mix up. Once you understand what kilowatts measure and what limits your real-world charging speed, station listings suddenly make sense.

kW vs kWh: power vs energy

• Kilowatts (kW) measure power — the rate at which energy flows. Think of it like the width of a pipe.
• Kilowatt-hours (kWh) measure energy — the total amount stored or delivered. Think of it like the volume of water.

A 100 kW charger delivering power for 30 minutes provides about 50 kWh of energy (100 kW × 0.5 hours). If your car uses ~3 miles per kWh, that's roughly 150 miles added.

Why you rarely hit the charger's rated speed

A station advertised at "350 kW" almost never delivers 350 kW to your car for the whole session. Your actual speed is the lowest limit among several factors:

1. Your car's maximum charge rate. Many EVs peak at 100–250 kW; some lower-cost models top out around 50–100 kW. A 350 kW charger can't push more than your car accepts.
2. State of charge. Charging slows as the battery fills. You'll see peak speeds at low charge and a steep drop-off after ~80%.
3. Battery temperature. Cold batteries charge slowly until they warm up; preconditioning helps (more in our preconditioning guide).
4. Shared cabinets. Some stations split power between two stalls, so a neighbor plugging in can cut your speed.

Reading a station listing

When you see a charger listed at a certain kW, treat it as a ceiling, not a promise. What you actually care about is:

• Is the rated power at least as high as your car can accept?
• Is the station available so you get the full cabinet?
• Are you arriving at a low state of charge so you're in the fast part of the curve?

The practical upshot

For day-to-day charging, kW barely matters — you're parked anyway. For road trips, kW is everything: a higher-power station that matches your car's peak rate gets you back on the road faster. ChargeScout shows max power in kW on every station and lets you filter by minimum charge level, so you can quickly spot the stations that will actually charge your car quickly. For the bigger picture, see DC fast vs Level 2.