Can You Charge a Tesla with Portable Solar Panels?


It’s 2020, and electric vehicle sales are booming. People are looking for the most efficient and cost-effective ways to charge their automobiles while on the move, a regularly debated option being the use of portable solar panels. We have dived into the information and crunched the numbers to answer the burning question – Can you charge a Tesla with portable solar panels?

Technically speaking it is possible to charge an electric vehicle such as a Tesla using any size solar panel. But it is not practical to use portable solar panels to do so. Electric vehicles use a lot of energy, considerably more than a single portable solar panel can create in over 100 days of glaring sunshine. You would need a substantial number of panels and uninterrupted sunlight to get your car moving again. 

There is a lot more to know about this question, so we have done the math to provide concrete evidence in this post! Keep reading as we break down the numbers and analyze the possibility of portable solar charging for Tesla EV’s.  

Getting to know your portable solar panel

There are three main factors that will determine the energy output of your portable panel: panel size, material and amount of sunshine. The average portable solar panel on the market today will have a maximum output of between 150-200 watts. 

Electrical energy is commonly measured in kilowatt-hours, this being a composite unit equal to the power consumption of one thousand watts for one hour.

Kilowatt-Hour (kWh) = Watts x Time (hrs) / 1000

So if you have a 200W panel in 7 hours of sunlight it will generate 1.4 kWh (kilowatt hour) – it is important to keep in mind that this is the optimum output in direct midday sunlight, most panels will have an efficiency rating of ~20% making the output considerably less.

Furthermore, solar panels produce DC (direct current) and a Tesla charging port accepts AC (alternating current). This means you must also carry an inverter to convert DC to AC, allowing for further voltage loss and less efficiency. 

What does this maths mean in reality?

We understand that math is scary, but stick with us!

With modern Tesla’s featuring battery capacities of 100 kWh, the output from one panel in one day will charge your vehicle enough to travel just 3 miles. In reality it would be a lot less than this, as it is impossible to guarantee 7 hours of uninterrupted sunshine. A little more math and you will find that one week of continuous charging will give you only 20 miles. 

It is clear that charging a Tesla with just one panel is not an option – the output is nowhere near enough to power the energy use required to move an electric vehicle.

Can you use multiple portable panels?

Multiple solar panels can be connected to form what is known as a solar array, which works as one system to generate a higher output of energy.

Depending on what part of the world you’re located in, you will be receiving differing amounts of sunlight. For arguments sake let’s pretend we are in the USA, where on average there will be ~7 hours of sunlight per day. 

To completely charge your Tesla battery from 0% to 100% using nothing but portable solar panels, you would need an array of 75 perfectly efficient PV modules in continuous midday sunlight for 7 hours. This is an obscene number of panels in impossible conditions. 

The practicalities of charging a Tesla with portable solar panels

As we stated at the beginning of this article, it is certainly possible to charge your Tesla using portable solar panels. However, there are a multitude of factors we now must consider answering why it is not a viable option (yet).

Our calculations may be a bit generous

All these calculations have been extremely generous with the energy output of the panels. Solar panels do not produce a continuous amount of energy from dawn to dusk.

High noon is obviously where maximum output is achieved and all hours before and after this will generate a fluctuating amount of power. 

As previously mentioned, low panel efficiency and voltage drop from the inversion process further adds to this loss of energy.

This reveals that achieving a full charge (0% – 100%) in one day using portable solar panels is impossible.

Transporting the “portable” solar array

We know it will take a vast number of panels to charge your Tesla, so how do we make this portable? 

The only way would be to tow your panels in a trailer behind your vehicle (which in turn would decrease the range of your vehicle due to increased weight). 

An important note – no model of Tesla vehicles come with a tow bar so custom additions would need to be made.

Area of panels required

When panels are connected, they form what is known as a string. Multiple strings form an array. Now, these strings are no longer acting as individual panels but as one unit, and if one panel becomes shaded the entire string is affected. 

Therefore, to charge your Tesla with these portable panels, an extremely large unshaded area is required. And unless you are carrying an axe or willing to trespass on private farmland, you may struggle to find such a space.

Complicated set up 

It is important to remember that with a high number of panels, dangerously high voltage is involved.

There is also the tedious process of setting up and plugging in 75 individual panels. The DC cabling and an inverter must also be set up correctly to ensure the safe conversion of power into your Tesla. If you are not a trained electrician this will prove to be an extremely daunting task and by the time you complete the setup, you will most likely have lost hours of valuable sunlight! 

Furthermore, unless you are charging your Tesla on the equator, your panels must be angled correctly (in relation to your longitude and latitude) to achieve optimum efficiency. This will require a structural frame if your chosen brand of panels are not self-supporting.

Time & Weather

Now, as if by some form of miracle you have managed to set up your array, you are in for a 7-hour wait on the side of the road in (hopefully) scorching sunlight. 

Nobody can guarantee a perfect climate and your panels will be susceptible to local weather such as cloud cover, haze and atmospheric conditions. All these factors will decrease the energy output of your system.

Expense

With the price of 200W portable solar panels averaging upwards of USD$200, you are looking at an overall cost of USD$15,000 just for the panels. The additional need for a trailer, inverter, and cables will increase the final cost to over USD$20,000.

It would be much wiser to use this money to install a large solar system on your house, which could power household devices and charge your Tesla (while parked at home). The panels that are installed on roofs have a much higher energy output than their portable cousins, and with the option to install batteries to store unused electricity this is undoubtedly the better decision. 

What does Tesla say?


Tesla CEO Elon Musk suggested in 2017 that the model 3 would come with a solar panel integrated into the roof of the vehicle. He later walked back on this statement admitting that it would be “not that helpful, because the actual surface of the car is not that much, and cars are often inside. The least efficient place to put solar is on the car.”

The engineering mogul has since confirmed, ahead of its 2021 release, that the much anticipated Cybertruck will have a deployable solar roof option, capable of adding 15 miles a day. Musk has also hinted at solar wings that will be able to fold out to further increase the mileage of the electric pickup truck.

With Tesla leading the charge of EVs it is exciting that they have now opened the door to integrated solar panels. This will inevitably start an “arms race” between other electric vehicle companies as they experiment and innovate to create solar charging options.

In the future?

Charging a Tesla with portable solar panels is simply not a practical option with current technology. The portable panels on today’s market do not yield enough energy to efficiently charge up an electric vehicle. The future is promising, however.

Solar panel technology is improving exponentially, efficiency is increasing while costs are decreasing. Nobody knows where solar tech will be in 20 years’ time, but the future certainly looks bright (no pun intended). With this improved efficiency, perhaps charging a Tesla with portable solar panels will become a viable option – we will just have to wait and see. 

Lloyd Heathfield

Lloyd Heathfield is a Biological Science graduate who has always had a passion for innovative technology, especially that of an environmental nature. Lloyd now works in the solar energy sector.

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