Your guide to calculating the energy consumption of an electric vehicle

With traditional cars that are powered by petrol or diesel, it is simple to calculate how long you have got before you need to pull over and fill up again.

You have a tank with a defined size and a rating for your car of litres per 100 kilometres, plus a reliable fuel gauge that will tell you precisely how many kilometres you have left to drive before you run out.

There are some variables, like highway and city driving, along with wind resistance to a certain degree – but in general, you know how much petrol you need to get to your destination, and the risk of running out is pretty low.

With electric vehicles (EVs), calculating the consumption is not quite as clear cut. You do have a battery that has a defined capacity, but there is a range of factors to consider when calculating how far you can travel on a single charge.

Is it cheaper to charge an EV than a petrol or diesel car? 

This is the first important distinction and yes, it is significantly cheaper to power an EV – even if you are using a wall socket at your own home where you are paying the bill.

An average petrol vehicle is going to consume around five litres of fuel every 100km, while an EV will use approximately 15kWh of charge over the same distance.

The cost of petrol in Australia on average is around $1.41, which means you will pay about $7.05 for five litres of fuel. The average cost of 1kWh of electricity in Australia is around $0.30 or around $1.50 for 4kWh, which means it is much cheaper to power an EV, especially if you can access free charging stations around the country.

There are factors that will impact your consumption

This is important to factor in when you are planning a trip in your EV. You cannot assume that 5kWh is comfortably going to give you 100km of driving time, as there are many factors that can impact the consumption of your vehicle that need to be considered, including:

Aerodynamic drag: Most EVs have been specifically designed to be as aerodynamic as possible, which is why they look different to tradition models. Extreme wind conditions can reduce the distance you will be able to drive before needing to re-power.

The energy required to accelerate: The more you load up your car, the more oomph you are going to need in order to accelerate. If you are the sole driver, you are going to get a lot further on a single charge than you would with the entire family in the vehicle.

Friction: The angle and surface of the road you are driving on will impact your consumption.

Inefficiencies: If the motor, battery or inverter is starting to degrade, they are not going to be as efficient and you will not be able to travel as far.

So consider all of these factors when you are setting out in an EV, and make sure you compensate to allow yourself plenty of time to reach your next recharging station.