EV energy explained
New to electric cars? Most of the jargon comes down to two ideas: energy (kWh, how much is stored or used) and power (kW, how fast it flows). These free tools turn them into miles, hours and pounds.
Use the calculators below, or start with the kW vs kWh explainer if the terms are new.
- kWh to milesConvert kWh to miles for an electric car: enter your miles per kWh to get range from any amount of energy, or the kWh needed for a journey.
- Efficiency converterConvert EV efficiency between miles per kWh, Wh per mile, kWh per 100 miles, kWh per 100 km and km per kWh, using exact factors.
- Charging timeEstimate how long an electric car takes to charge from any start to end percentage, on any charger from a 3-pin plug to a 150 kW rapid charger.
- Charging costWork out what it costs to charge an electric car and compare pence per mile with petrol, using your own tariff, efficiency and fuel price.
- Range calculatorEstimate electric car range from battery size in kWh and efficiency in miles per kWh, with an adjustment for cold weather or motorway driving.
- kW vs kWhkW measures power and kWh measures energy. A plain-English explanation with EV examples: charger speed, battery size and charging time.
- GlossaryA plain-English glossary of electric car terms: kWh, kW, Wh per mile, usable capacity, AC and DC charging, Type 2, CCS and state of charge.
- AI charging planEnter your trip distance, range, battery size and charging preferences to get a practical AI-made charging plan for a UK electric car journey.
Typical charging speeds
| Charger | Power |
|---|---|
| 3-pin plug | 2.3 kW |
| Home wallbox | 7 kW |
| Three-phase AC | 11 kW (up to 22 kW) |
| Rapid DC | from about 50 kW |
| Ultra-rapid DC | about 100 kW to 350 kW |
Frequently asked questions
What is a kWh in an electric car?
A kilowatt-hour (kWh) is a unit of energy. An electric car's battery size is measured in kWh, and so is the electricity you pay for. Roughly 3 to 4.5 miles per kWh is typical for modern electric cars in mixed driving.
What is the difference between kW and kWh?
kW measures power, how fast energy flows, such as charger speed. kWh measures energy, how much there is, such as battery size. 1 kW for 1 hour is 1 kWh.
What size battery do I need?
Multiply the miles you want between charges by your car's energy use. At 3.5 miles per kWh, 200 miles needs about 57 kWh of usable battery.