Nearly one in 10 new car sales in Australia is an electric car. When it comes to charging EVs, Australians like to do it at home. It’s estimated that 70 – 85% ¹ of EV owners charge from home. Not only that, but over 50% ² of all owners charge their EVs from electricity generated from their own solar panels.

Calculating how many solar panels you need to offset your EV charging is easier than you might think — it all comes down to understanding a few key variables and how they work together.

There are three key variables to calculate how much solar is needed to charge an EV:

• Size or battery capacity of the car
• Average vehicle usage
• Energy required to charge the car
• Solar generation potential at the charging location

In this article, we’ll uncover how much solar energy is needed and what size solar system you require to charge your electric vehicle (EV) based on the top 10 highest-selling electric vehicles in Australia and the national driving averages.

Average EV battery capacity

The table below displays the ten highest-selling electric vehicles (EV) in Australia for 2024. All models offer at least two, and often more, battery capacity options that will affect the purchase price. Just like more power in an ICE (Internal Combustion Engine) vehicle, larger batteries are viewed as a “premium” feature and will inherently cost more than the entry-level vehicles with smaller batteries.

Most popular EVs in Australia in 2024

Average EV usage & efficiency

How often and how you drive your electric vehicle both play a significant role in determining your energy consumption and charging requirements.

Just like an ICE vehicle, the way you drive – acceleration behaviour, brake behaviour, commute speed, etc. – all play a significant role in determining your car’s energy (kWh) consumption.

ICE vehicles tend to have predictable fuel consumption patterns. As a general rule, stop-start traffic will eat into your fuel efficiency. Modern stop-start tech will do its best to curb this behaviour, but the rule remains – if you spend more time in stop-start traffic, your ICE vehicle will use more fuel. The most fuel-efficient speed for ICE vehicles is typically around 80-90 km/h – gentle freeway cruising speeds.

EVs, on the other hand, excel in stop-start traffic, which is part of what makes them such an appealing proposition for city-dwellers and peak hour commuters. Stop-start traffic allows EVs to use regenerative braking to convert braking energy back into usable electric energy.

EV owners with a city commute are far more likely to get closer to the advertised WLTP (Worldwide Harmonised Light Vehicle Test Procedure) range than EV drivers who spend most of their time at higher speeds on the highway.

Average energy required to charge an EV

Australia’s best-selling EV, the entry-level Tesla Model Y with a 60-kWh battery, has an advertised WLTP range of 466km, indicating an operating efficiency of 12.88 kWh / 100km. Like ICE fuel consumption figures quoted by manufacturers, WLTP figures are notoriously optimistic. Still, most drivers will report around 12 – 15 kWh / 100km of energy usage, which is vastly more efficient than when EVs first came onto the market.

The most recent data from the Survey of Motor Vehicle Use by the Australian Bureau of Statistics from 2020, shows that the average yearly distance travelled by Australian motorists is 12,100km.

If we take a conservative average kWh / 100km consumption figure of 15 kWh / 100 km and say that the average EV battery size is 60 kWh, then a full charge would deliver around 400 kms of driving range, which would require 30.25 full battery charges each year (12,100 / 400).

So then, for the sake of very simple science, if we take all variables out of the equations (partial charges, use of public charges, changes to consumption) and we say that an EV with a 60 kWh battery needs to be charged from 0-100% 30.25 times each year to reach the national average of 12,100km, we would require 1,815 kWh (30.25×60) of energy to achieve this.

Average solar system output by size

The size of your solar system is the biggest determining factor in its potential for energy production. However, when we look at “average solar system output by size”, there are two other important variables that we need to consider:

• Average sunshine hours at your location
• Property specific conditions

The table below shows the average daily energy produced by different solar systems in one of Australia’s lowest producing states, Victoria (VIC), and one of its highest producing states, Western Australia (WA).

Again, it’s important to reiterate that these are average figures. Energy consumption could be higher or lower depending on your solar system and weather conditions.

Solar system size to charge an EV

Based on the average EV requiring 1,815 kWh to cover the national driving average of 12,100km per year or 33.2km per day (12,100 / 365), a 1.5kW panel system is enough to power the EV alone. The table below shows output for a 1.5kW system in Melbourne, Victoria:

These calculations are based on average figures. During winter months with lower sunshine hours, your system will not produce as much energy.

Solar system size to power your home and charge an EV

Of course, you will also want to power your household electricity usage with solar energy. In Victoria, a 5kW solar system generates around 18 kWh per day, or approximately 6,570 kWh per year, which is enough to cover the average household electricity usage of between 16 – 18 kWh per day.

Therefore, adding an extra 1.5kW to this system should be enough to power your home’s electricity needs and charge an EV. For average usage, a 6.6kW system is about right.

Even after accounting for other household energy needs, an appropriately sized solar system can comfortably cover the energy required for EV charging, dramatically reducing or even eliminating reliance on the grid for vehicle charging.

Everyone’s needs are different

We have based our calculations on average usage and solar production figures. We recommend you perform your own calculations. For the solar component, our solar panel calculator will give you the figures you need.

Then factor in roughly 1.5kW – 2kW per EV that you want to charge.

Number of solar panels required to charge an EV

The number of solar panels required to charge your EV will depend on the size of system that you opt for. Using the example above where a 6.6kW system would be enough to cover both EV and average household usage, 15 to 20 solar panels would be required to charge an electric vehicle (EV).

Offsetting your commute

Offsetting your electric vehicle (EV) with solar is easier and cheaper than you think. The average cost of a 6.6kW solar system across Australia is around $6,500 – depending on your location and your chosen system.

It costs between $17.25 – $22.50 to charge a Tesla at home, these costs can almost entirely be offset by using solar energy. Bear in mind, it takes between 6 – 9 hours to charge a Tesla using a home EV charger. For EV owners, solar is a smart way to offset your environmental impact and maximise your savings.

Sources:
¹ EV owner survey
² EV owner insights