A kilowatt-hour (kWh) is the standard unit used to measure both how much energy an EV’s battery can store and how much electricity you use to charge it. It shows up everywhere in EV ownership, on your electricity bill, in your vehicle’s specifications, and at public charging stations, so understanding it makes the rest of EV ownership click into place.
Breaking down the unit
A kilowatt (kW) measures power, the rate energy is being used or delivered at a given moment. A kilowatt-hour measures energy, the total amount used over time. Running a 1 kW appliance for one hour uses 1 kWh of energy. Running a 2 kW appliance for the same hour uses 2 kWh. It’s the same relationship as speed versus distance: kW is how fast energy flows, kWh is how much has actually been delivered.
| Where you’ll see it | What it tells you |
|---|---|
| Battery capacity (e.g., “77 kWh battery”) | The total amount of energy the battery can store when fully charged, roughly comparable to a gas tank’s size |
| Electricity bill (cents per kWh) | What you’re charged for each unit of electricity used, this rate is what determines your actual charging cost |
| Charger output (e.g., “11 kW charger”) | How fast energy is delivered, a higher kW rating charges the battery faster, assuming the vehicle can accept that rate |
| Efficiency rating (kWh per 100 km) | How much energy the vehicle uses to travel a given distance, lower is more efficient, similar to L/100km for a gas car |
A simple example
A vehicle with a 60 kWh battery and an efficiency rating of 18 kWh per 100 km can travel roughly 330 km on a full charge (60 divided by 0.18). Charging that same 60 kWh battery from empty at a home electricity rate of 10 cents per kWh costs about $6. This is the same math behind our charging cost calculator and range calculator, just automated so you don’t have to do it by hand.
💡 Tip: When comparing EVs, pay attention to the kWh-per-100km efficiency figure alongside battery size and range. A smaller battery achieving similar range to a larger one is the more efficient vehicle, worth knowing when comparing models. See our guide on how to compare EV ranges for more.
⚠️ Note: Don’t confuse kWh with kW when reading a vehicle’s specs or a charger’s rating, they measure different things, and mixing them up is a common source of confusion when estimating charging times or costs.