kW (kilowatt) measures power — how fast energy moves at a given moment. kWh (kilowatt-hour) measures energy — how much has moved in total. The two answer different questions: kW tells you the speed of a charging session, kWh tells you the size of the tank.
The fuel analogy
With gasoline, gallons measure how much you buy and gallons-per-minute measures how fast the pump flows. Electric energy works the same way: kWh is the gallons, kW is the flow rate.
Typical figures
- Level 1 (household outlet): roughly 1–2 kW — slow overnight top-ups.
- Level 2: roughly 7–19 kW — the everyday workhorse for home and destination charging.
- DC fast: roughly 50–350 kW — quick sessions whose speed drops as the battery fills.
Why it matters for a reserve
Because EV efficiency is commonly expressed in miles per kWh, a modest amount of stored energy translates directly into driving distance. That relationship — not raw power — is what makes a portable reserve useful as a bridge to the next working charger. Many EVs fall between 2.5 and 4 miles per kWh, though the exact figure depends on the vehicle and conditions.