Miles per kilowatt-hour (mi/kWh) is an important metric that tells EV owners how many miles an electric vehicle can travel on a single kilowatt-hour of electricity.
This allows us to compare the energy efficiency of different EV models and assess their total range.
This article provides an introduction to the concept of mi/kWh, explaining why EV owners need to understand it, how to calculate it, and how it influences EV performance.
What does Miles per kWh (mi/kWh) mean?
Miles per kWh (mi/kWh) is a unit of measurement that indicates the distance travelled by an EV in miles per kilowatt-hour of energy consumed. It represents the energy efficiency of the vehicle and provides an estimate of how many miles the EV can travel on a given amount of electrical energy.
A higher Miles per kWh value would suggest that a car has better energy efficiency and that the EV can travel more miles for each kilowatt-hour of electricity consumed.
On the other hand, a lower Miles per kWh value suggests lower efficiency, meaning the vehicle covers fewer miles for the same amount of energy.
How is Miles per kWh (mi/kWh) calculated?
Miles per kWh (mi/kWh) is calculated by dividing the distance travelled in miles by the amount of energy consumed in kilowatt-hours. The formula for calculating Miles per kWh is:
Here’s an example Miles per kWh (mi/kWh) calculation:
John’s electric car travelled a distance of 100 miles from Norwich to London and consumed 25 kilowatt-hours of electricity during that journey.
The Miles per kWh calculation would be: Miles per kWh = 100 miles / 25 kWh = 4 mi/kWh
In this case, my car had an efficiency of 4 miles per kilowatt-hour, meaning it travelled 4 miles for every kilowatt-hour of energy consumed.
What is a good Miles per kWh (mi/kWh)
Understanding what is good Miles per kWh (mi/kWh) helps us better understand the energy efficiency of electric cars.
The table below shows a breakdown of Miles per kWh categories along with their energy consumption and an approximate distance.
|Miles per kWh Performance||Miles per kWh Range||Distance per 10 kWh (Miles)||Distance per 10 kWh (Kilometers)||Distance per 100 kWh (Miles)||Distance per 100 kWh (Kilometers)|
An EV with a good Miles per kWh (mi/kWh) sits between 4.0 to 4.9 mi/kWh.
This means it can cover approximately 40-49 miles (64-79 kilometres) per 10 kWh of energy or 400-490 miles (640-790 kilometres) per 100 kWh of energy.
An EV with a superior Miles per kWh ratio (5.0 or above), can travel 50 miles (80 kilometres) or more per 10 kWh of energy or 500 miles (800 kilometres) or more per 100 kWh of energy.
What is Watt-hours per mile (wh/mile)?
Wh/mile tells you how much electricity an electric vehicle uses to travel one mile. Lower Wh/mile means it uses less electricity per mile, which is better.
It represents the amount of electrical energy, measured in watt-hours. Wh/mile is similar to Miles per kWh (mi/kWh). Let’s look at this further…
Watt-hours per mile (wh/mile) VS Miles per kWh (mi/kWh)
- Watt-hours per mile (wh/mile)
Wh/mile, or watt-hours per mile, tells you how much electricity an electric car used to travel a distance of one mile.
It measures the specific amount of electrical energy needed for each mile travelled. A lower Wh/mile value indicates that the EV is using less electricity per mile, which is generally considered better because it means the vehicle is more energy-efficient.
- Miles per kWh (mi/kWh)
Miles per kWh (mi/kWh), on the other hand, tells you how many miles an EV can travel using one unit of electrical energy, specifically one kilowatt-hour (kWh).
A higher Miles per kWh value means the vehicle can travel more miles for each kilowatt-hour of electricity, indicating greater efficiency.
To simplify further, Wh/mile tells you about electricity usage per mile, whereas Miles per kWh tells you about miles travelled per unit of electricity. Both metrics are important for understanding the energy consumption and efficiency of EVs, but they approach the topic from slightly different angles.
How to calculate Watt-hours per mile (wh/mile)?
To calculate Wh/mile, the energy consumption in watt-hours is divided by the distance travelled in miles.
For example, if an electric vehicle consumes 300 watt-hours of energy to travel 100 miles, the Wh/mile value would be 300/100 = 3 Wh/mile.
What is kilowatt-hours per 100 miles (kWh/100 miles)?
kWh/100 miles (kilowatt-hours per 100 miles) is how you measure the energy consumption of an electric vehicle per 100 miles travelled.
It represents the amount of electrical energy, measured in kilowatt-hours (kWh), required for an EV to travel a distance of 100 miles.
kWh/100 miles is commonly used as a metric to compare the energy efficiency of different electric vehicles. It provides a standardised way to evaluate energy consumption across EV models and allows for easier comparison of their efficiency levels.
To calculate kWh/100 miles, the total energy consumption in kilowatt-hours is divided by the distance travelled in miles and then multiplied by 100.
For example, if an electric vehicle consumes 30 kWh of energy to travel 100 miles, the kWh/100 miles value would be (30/100) * 100 = 30 kWh/100 miles.
Miles per kWh (mi/kWh) to Mpg
Miles per kWh (mi/kWh) and miles per gallon (mpg) are both metrics used to measure the efficiency of vehicles but in very different ways.
- Miles per kWh (mi/kWh)
Miles per kWh (mi/kWh) is a measure of energy specifically for electric cars, it represents the number of miles an EV can travel on one kilowatt-hour (kWh) of electrical energy.
- Miles per gallon (mpg)
Miles per gallon (mpg) is a measure of fuel efficiency used for internal combustion engine vehicles, such as petrol or diesel cars.
It represents the number of miles a vehicle can travel on one gallon of fuel. A higher mpg value would show that a car has good fuel efficiency, meaning the vehicle can travel more miles on the same amount of fuel
The main difference between the metrics is the source of energy. Mi/kWh focuses on the efficiency of electric energy consumption, while mpg focuses on the efficiency of fuel consumption.
It’s hard to compare the Miles per kWh (mi/kWh) to the equivalent Miles per gallon (mpg) of a petrol car as they measure completely different forms of energy.
Which electric cars have the best Miles per kWh (mi/kWh) in the UK?
Let’s look at which electric cars have the best Miles per kWh (mi/kWh) ratings in the UK market:
- Tesla Model 3: 5.08 miles per kWh
- Renault Megane E-Tech: 4.87 miles per kWh
- Hyundai Kona Electric: 4.8 miles per kWh
- Volkswagen ID.3: 4.8 miles per kWh
- Renault Zoe: 4.59 miles per kWh
- Tesla Model 3, Standard Range Plus: 4.56 miles per kWh
- Tesla Model 3, Long Range: 4.54 miles per kWh
- Fiat 500e: 4.57 miles per kWh
- Peugeot e-208: 4.5 miles per kWh
- MINI Electric: 4.45 miles per kWh
- Niro EV: 4.39 miles per kWh
- Citroen e-C4: 4.38 miles per kWh
- Hyundai Ioniq Electric: 4.19 miles per kWh
- BMW i3: 4.16 miles per kWh
- Mini Electric: 4.1 miles per kWh
- Seat Mii electric: 4.1 miles per kWh
- Volkswagen e-up!: 4.07 miles per kWh
- Smart EQ fortwo: 4.05 miles per kWh
At the top of the list, the Tesla Model 3 has an impressive rating of 5.08 mi/kWh. This demonstrates its exceptional efficiency, allowing drivers to travel further on each charge.
The Model 3’s high energy efficiency is likely attributed to Tesla’s advanced electric drivetrain and cutting-edge battery technology.
Following closely is the Renault Megane E-Tech, offering a commendable 4.87 mi/kWh. The Megane E-Tech demonstrates Renault’s commitment to electric mobility with its efficient powertrain, providing a balance of performance and range.
The Hyundai Kona Electric and Volkswagen ID.3, tie at 4.8 mi/kWh. The Renault Zoe, known for its compact and practical design, achieves 4.59 mi/kWh. The Zoe’s energy efficiency combined with its affordable pricing makes it a great option for urban commuting and everyday driving.
Among the top-ranking electric cars, it’s worth highlighting the Tesla Model 3 variants. Both the Standard Range Plus and Long Range models achieve impressive energy efficiency ratings of 4.56 and 4.54 mi/kWh, respectively. Tesla’s consistent focus on optimising range and efficiency allows these models to deliver exceptional performance while minimizing energy consumption.
Other notable models include the Fiat 500e, Peugeot e-208, and MINI Electric, all of which achieve mi/kWh ratings above 4.4. The inclusion of these cars in the best Miles per kWh list shows that smaller and more compact electric cars can still offer competitive energy efficiency.
What is the average Miles per kWh (mi/kWh) for electric cars
On average, electric cars in the UK achieve Miles per kWh (mi/kWh) ratings ranging from around 3 to 4.5 mi/kWh. The Miles per kilowatt-hour (mi/kWh) for electric cars will vary depending on several factors. Factors such as driving conditions, weather, terrain, driving speed, and personal driving habits can significantly impact the actual efficiency experienced by an electric car owner.
Watt-hours per mile (wh/mile) to Miles per kWh (mi/kWh)
To convert from watt-hours per mile (Wh/mi) to miles per kilowatt-hour (mi/kWh), you need to perform a unit conversion. Here’s how you can convert from Wh/mi to mi/kWh:
- Start with the given value in watt-hours per mile (Wh/mi).
- Divide the given value by 1,000 to convert watt-hours to kilowatt-hours. This will give you kilowatt-hours per mile (kWh/mi).
- Invert the value obtained in step 2 to get miles per kilowatt-hour (mi/kWh). This is done by taking the reciprocal of the value.
For example, if you have 250 Wh/mi, you would divide by 1,000 to get 0.25 kWh/mi. Then, take the reciprocal to get 4 mi/kWh.
What’s the difference between KW and kWh?
The main difference between kilowatts (kW) and kilowatt-hours (kWh) lies in the units they measure and the variables they represent.
Kilowatts (kW) measure power, which is the rate at which energy is consumed or produced.
Kilowatts represent the rate at which work is done or energy is used. For example, a 1 kW appliance uses 1 kilowatt of power every hour.
kilowatt-hours (kWh) measure energy consumption or production over a period of time.
Kilowatt-hours are obtained by multiplying the power in kilowatts by the time in hours. For example, if you have a 1 kW appliance running for 3 hours, it would consume 3 kilowatt-hours (3 kWh) of energy.
What impacts an EVs Miles per kWh (mi/kWh)?
Here are some key factors that can influence EV efficiency:
- Driving Behavior
Aggressive driving, such as rapid acceleration and hard braking, can decrease efficiency. Smooth and gradual acceleration, as well as maintaining a consistent speed, can help optimize energy consumption.
- Speed and Terrain
Higher speeds generally result in increased aerodynamic drag, reducing efficiency. Driving uphill or on hilly terrain also requires more energy compared to driving on flat roads.
- Temperature and Climate Control
Extreme temperatures, both hot and cold, can impact EV efficiency. Preconditioning the cabin while the vehicle is still connected to a home charger or a granny charger can help minimize the impact on driving efficiency.
- Tyre Pressure
Properly inflated EV tyres reduce rolling resistance, which can improve efficiency. Underinflated tires can increase friction, leading to higher energy consumption.
- Auxiliary Power Usage
Using features like heated seats, infotainment systems, and other electronics consumes additional energy. Minimizing the use of these features when not needed can help improve efficiency.
- Battery State of Charge
EV efficiency can vary based on the battery’s state of charge. Some EVs experience reduced efficiency when the battery is nearly empty or fully charged. Maintaining the battery charge within a recommended range may optimise efficiency.
- Regenerative Braking
Utilising regenerative braking, which recaptures energy during deceleration and braking, can improve overall efficiency. It helps convert some of the vehicle’s kinetic energy back into electrical energy, which can be stored in the battery.
Calculate your EVs range with Miles per kWh (mi/kWh)
To calculate the range of an electric car using miles per kilowatt-hour (mi/kWh), you need to know the capacity of your EV’s battery in kilowatt-hours (kWh). Here’s the formula to calculate the range:
Range (in miles) = Battery capacity (in kWh) * mi/kWh
For example, let’s say your EV has a battery capacity of 60 kWh and an efficiency rating of 4 mi/kWh. Using the formula:
Range = 60 kWh * 4 mi/kWh = 240 miles
So, with a fully charged battery, your EV would have an estimated range of 240 miles.
The final word on Miles per kWh (mi/kWh)
Miles per kilowatt-hour (mi/kWh) represents the distance an EV can travel on a single kilowatt-hour of energy. It serves as an easy-to-understand measure of how far an EV can go on a given amount of energy.
A higher mi/kWh ratio means that the vehicle can travel more miles per unit of electricity consumed, resulting in a longer driving range and potentially reducing the need for frequent recharging.
However, it’s important to remember that real-world range can be influenced by various factors, such as driving conditions, temperature, terrain, and personal driving habits.
Ready to dive even deeper...
John is the Editor and Spokesperson for Electric Car Guide.
With over 20 years of writing experience, he has written for titles such as City AM, FE News and NerdWallet.com, covering various automotive and personal finance topics.
John’s market commentary has been covered by the likes of The Express, The Independent, Yahoo Finance and The Evening Standard.