How Many Solar Panels To Charge An Electric Car?

Charging your EV using the sun is essentially running your car on sunshine, but several factors contribute to calculating how many solar panels you need to charge your car.

At a Glance:
1️⃣ The average electric vehicle would require between 8 and 12 solar panels to charge it.

2️⃣ The battery size, the panel wattage and speed of charge, and your location would all influence the number of panels and charging time.

3️⃣ To accurately determine the number of panels, you would need to know the miles per kWh(Mi/kWh), Kilowatt hours per 100 miles (kWh/100 Miles), and the miles per gallon equivalent (MPGe).

Factors Affecting The Number Of Solar Panels Required

As with PV, the number of solar panels you need to charge an EV will depend on how much solar energy your panels receive, their efficiency, their wattage as well as the battery capacity of the EV itself, so let’s look at these factors independently and then apply it to a practical example.

Aside from these factors, you also need some basic information on your EV to determine how far you would get per kWh of charge, how many kWh you’d need for 100 miles, and the energy efficiency measured in MPGe.

How Much Solar Power Would You Need To Charge Your EV For A Year?

On average, people drive around 14000 miles per year, according to the Federal Highway Administration. While this may vary slightly from state to state, this number is considered an accurate average.

An average EV can do about 3 miles per kWh, so powering your EV for a whole year will require 4666,66 kWh of energy. 

Within an average-sized PV system, every installed kW would produce around 4 kWh per day or approximately 1500 kWh per year.

So to have enough capacity to charge your EV would require an additional 3,1 kW, which would be between 8 and 12 solar panels, depending on the wattage.

For 400W panels, you would need eight; for 300W panels, you would need 11.

Battery Size Determines The Number Of Solar Panels Needed

The biggest single factor is the size of the battery, and most EVs have batteries that range in size from 25kWh to 100kWh.

Let’s look at some EVs and their battery sizes to determine how many solar panels they would need to charge based on their location in the USA.

You can see that the influence of the solar radiation level impacts the number of panels needed to charge the respective EVs. 

If you look at the Audi E Tron with a 95kWh battery, it needs 11 solar panels if you are in the South Western US and 15 if you are in the North Eastern US – this is a difference of 36%, while other EVs require around 25%-33% more solar capacity between the North and South.

💡 Related Article: Best Time To Charge With Solar

The Type Of Charger You Use Determines The Charging Speed

But, as with most things solar, the number of panels and generated capacity are not the sole factors in determining how fast your EV would charge – the type of charger used also has a major role.

Remember that your charge will flow from the solar panels to the inverter and then to the EV charger installed, and whether this is a 120V level 1 or 240V level 2 charger will determine how fast the EV will reach full charge.

A level 1 charger can be between 1,4kW and 3,6kW, while level 2 chargers can deliver between 5kWh and 22kWh. 

For example, if we take the Chevy Bolt with a battery capacity of 60kWh, a level 1 charger at 3,6kW would take around 16.6 hours to charge the battery from flat to 100%.

A 22kW level 2 charger would take around 3 hours to charge the battery from empty; also, remember that the first 10% of charging and the last 10% take longer than 20%-90%.

Manage And Monitor Your Charging 

When using solar panels to charge your EV, you can monitor the charging output using the inverter app, as this will tell you how much charge the system is drawing. 

By measuring the charging level before plugging in your EV and after, you can determine how much power is being distributed to the charging circuit.

But, to save you the trouble, you can get solar EV chargers that integrate with your inverter, and these use apps to control and divert charge from the panels to the EV, and they also have solar monitoring and control systems.

If you have an existing solar roof installation and want to use it to charge your EV. You must ensure enough capacity before connecting your level 1 or 2 chargers.

It would also be advisable to consider a bidirectional EV charger so that your fully charged EV battery could potentially charge your home or business.

Let’s Apply This To A Hypothetical Example

Now that we have the nitty-gritty of charging your EV using solar panels let’s apply this to a practical scenario with an EV with a 75kWh battery like the Tesla Model 3.

Using a 250W solar panel as an example, which can produce around 30-40 kW of AC power every month, would create 1kW per day in low solar conditions– so for a 75kWh battery, you would need 75 solar panels to produce the battery’s capacity in one day.

However, you won’t need to put 75 panels on your roof because the EV would only use around 12kWh per day, the equivalent power consumption of driving about 37 miles, an average daily range.

So how many solar panels do you need? At this range, you would only need around 12 solar panels, and if you increase their efficiency and size, you would require fewer panels to recharge the 75kWh battery.

Key Takeaways

The key points to remember are battery size and your location:

1️⃣ The number of solar panels needed to recharge an EV will depend on the battery size and the quantity of solar radiation based on your location.

2️⃣ EVs with smaller batteries would require between 6 and 8 solar panels, while larger batteries would need between eight and twelve solar panels.

Charging speed depends on the charger’s kW capacity- the larger the capacity, the faster the EV will charge.

And finally, solar EV chargers are available that integrate with existing inverters and PV systems, and bidirectional chargers are preferable.

🎓 Resources:
EV Charging With Solar | What You Need To Know
How Much Power Will An EV Use In A Year?
Lowering Your EV Charging Cost With Solar Panels And The IRS Benefits