How Many Solar Panels Does It Take To Charge An Electric Car?
How Many Solar Panels To Charge An Electric Car?
Over the past few years there has been a massive increase in the demand and usage of electric vehicles (EV) due to their increasingly high mileage range and minimum impact on the environment, compared to a traditional internal combustion engine.
If you are purchasing an electric vehicle, you should also consider buying or upgrading your current solar setup.
An electric vehicle coupled with a solar setup for charging is not only more economical but also saves you from the hassle of charging your EV at commercial charging stations.
Becoming more independent of traditional energy supplies just makes sense for the future – whatever it brings, it isn’t going to get any easier!
In total for an electric car with battery capacity of 40kWh (such as the Nissan Leaf) and a daily commuting distance of 30 miles, 7 solar panels of 250 watt rating would be required to charge the battery.
The big questions are how many solar panels are needed to charge an electric car and what would be the total cost of the setup?
Other factors you need to consider relate to feasibility, payback period and the inevitable maintenance costs associated with a solar panel charging system.
Contents
Can You Charge An Electric Car With Solar Panels?
Many electric vehicles use a battery as their only power source, while some use a hybrid approach, combining and electric motor with traditional power sources. Different electric vehicles have batteries of different capacity.
The Audi eTron has a battery storage capacity of 95 kWh of energy, whereas another electric vehicle the Nissan leaf comes in two modules having a battery capacity of 40kWh and 62 KWh.
A typical hybrid battery size may be only several kWh. For example, the Ford Fusion Energi has a battery capacity of just 9kWh.
Our entire solar setup involves two main parts – solar panels and a solar charge controller or regulator. Solar panels consist of numerous photovoltaic cells that generate an electric field under the influence of sunlight.
Coupled with some other parts this electric field produces usable energy in the form of Direct Current.
This direct current is then fed to a battery using a solar charge regulator that ensures your battery is properly charged and not damaged.
Can You Charge A Nissan Leaf With Solar Panels?
This is the procedure to follow when calculating the number of solar panels needed to charge the Nisan Leaf, with the battery option of 40Kwh.
Step 1. How much solar power do we need to charge a Nissan Leaf?
In our case, we may need to charge a 40kWh battery to full capacity, if completely depleted.
This is quite rare, as the average mileage per day travelled by EV owners is around 23 miles (37 km) – far below the total range of most electric cars (see table later on in this post).
This means we can apply a usage factor to the equation and reduce the number of solar panels required.
Step 2. The efficiency of Solar Panels – How much energy does a solar panel produce?
There are different types of solar panels in the market with different efficiencies. A conventional 250 W solar panel produces around 3040 KWh of DC power every month.
Let us assume our solar panel produces 35 KWh/month DC power. Dividing it by 30 we get a power output of 1.167 KWh/day.
Similarly dividing it by 24 we get 0.0486 KWh/hour. So, by using a conventional solar panel we get approximately 0.0486 KWh of energy every hour.
You can easily check the energy production of your proposed system by finding out the individual power output of the solar panels you plan on installing.
The manufacturer can provide this information in their technical specs, depending on the average insolation values in your area.
Step 3. What is the Mileage Range of your EV?
In the case of the Nisan Leaf with a 40 KWh battery, it can travel 243 km (or 151 miles) fully charged.
If we divide the range by the battery capacity, we get the milage per kWh.
For example, Nisan Leaf does 6.075km/KWh or 3.775miles/KWh (243km/40KWh or 151miles/40KWh).
Step 4. How long is the Daily Commute?
In Step 2 we established that our Solar panel has a power output of 1.167KWh/day.
Dividing the battery capacity by the power output gives us the number of solar panels we need. In our case, this comes to 34 solar panels (40KWh/1.167Kwh).
I know this number comes as shock to you but let us be realistic. It would be very unusual to have a battery in such a state of discharge.
The average distance a driver travels is 37 km or 23 miles per day.
If you work out your daily commute distance, then this figure would be used for your design calculations instead of the total range of the vehicle.
Here are a couple of examples:
 Battery capacity – 40KWh
 A typical 250 watt solar panel produces 1.167KWh/day
 The Nissan Leaf has a mileage of 151 miles/40KWh or 3.775miles/1Kwh
 Daily commute – 37 miles
 Battery capacity used is 40 x 37/150 = 9.8 kWh
 Number of solar panels need = Battery capacity used/single panel output = 9.8/1.167 = 8
In this example the daily distance to be traveled is 62 miles. To calculate the number of solar panels we divide the energy required to travel our daily distance by the energy produced by our solar panel per day.
 62 miles equates to 16.4609 KWh
 16.4609KWh/1.167KWh= 14 solar panels
How Many Solar Panels To Charge An Electric Car Calculator
These calculations were performed using conventional solar panels that are not the most efficient choice.
Using more efficient panels with higher energy production per day can reduce the number of panels required.
A single or dualaxis sun tracker (see later) would further reduce the amount of panels required by as much as 40%.
Are Solar Car Battery Chargers Effective?
After finding out the installation capacity of our solar setup an important question arises – Are they effective?
The effectiveness of solar car battery chargers can be determined using cost analysis. The majority cost incurred in a solar setup is the initial installation.
While prices of solar setups are different across the globe, every country is offering some type of subsidy for solar setups.
According to one study, the cost of electricity from solar is 0.06 Dollars/KWh whereas the average electricity cost from the grid is 0.1316 Dollars/KWh. The price difference is 0.0716 Dollars/KWh.
To put this in perspective, if you travel 100km (62miles) per day you would have a yearly saving of 424 Dollars.
In five years, you would save 2120 Dollars. The bigger the solar charger installation, the greater the savings.
Can You Charge An Electric Car With A Portable Solar Panel?
A short answer to this is: It might be ineffective but yes, they can charge your EV.
Nowadays you see many portable folding solar panels (FSP) that weigh as little as 10 pounds and are easy to carry anywhere.
A perfect analogy of portable folding solar panels would be that of a spare gasoline canister for your traditional combustion vehicles.
An average portable panel is usually 120W with an efficiency of 1530%. Very few of this type of panels offer builtin inverters.
If you have a 100 W portable panel it would take roughly 18 hours to charge a Nissan Leaf from a completely drained battery.
Of course, the greater the number of panels, the lower the charging time.
Can You Put A Solar Panel On An Electric Car?
Putting a solar panel on an electric car would be extremely inefficient for several reasons.
 The size of a car roof is roughly between 3040 sq ft. The solar panel installed would yield only 0.56 KW of power which is not nearly enough to power the car.
 Solar panels are heavy, on average weighing between 3040 pounds, unless flexible ones were used. Not only would they not produce enough power, they would actually decrease the car’s range rather than increasing it.
 The fact that the car is constantly moving, possible in cities where buildings block most of the sunlight, it would be nearly impossible to place the car such that the solar panel faces the sun at the right angle for a prolonged period.
How Many Solar Energy Storage Batteries Recommended?
The purpose of the solar energy battery is to conserve and store the unused solar energy produced through our solar panels.
This energy can then be used in the night time when solar panels are not producing energy or on a rainy day.
Using the data available from the U.S Energy Information Administration we can assume that an average household will use 30 kWh of energy per day.
A typical Solar battery can produce 10 kWh of energy, but that is when we neglect losses and assume that the battery runs at full potential – deep cycle batteries typically run at 90 percent depth of discharge, so only 9kWh is available.
In the case of our EV, we need roughly 16KWh of energy per day to travel 62 miles. Since we know that a typical battery can deliver 9KWh of energy in the absence of solar energy, we would need only 2 batteries to power us through the night or even longer.
Benefits of Fixed Array or Solar Tracking
Fixed solar panels arrays are the simplest and most common type of solar structure employed across the globe.
It consists of mounting the solar panel on a existing structure, which the name suggests, is fixed in place. However, solar panels operates at their maximum efficiency when the sunlight hits the panel perpendicularly.
As the sun moves across the sky this angle changes. As a result, the solar setup does not operate at its maximum efficiency for most of the day.
To compensate for this problem, platforms are available that can track the movement of the sun and placing the panels at a nearperfect angle to ensure maximum energy production. They can be either single or dualaxis.
The dualaxis not only follows the sun throughout the day like a single axis but also varies the vertical angle to compensate for seasonal changes.
In one study it was shown that solar tracking provides 40 percent more energy annually. This number is increased to 65 percent during Summers.
The trend is shown by the graph below:
Unfortunately, the initial investment cost and maintenance for solar tracking is much greater compared to the fixed array.
The choice between fixed array and solar tracking all comes down to whether you want to save some money upfront or save significantly more over a longer period.
A comparison of energy production through fixed and tracking solar panels is given below:
Payback Period For Solar Installations
To discuss the payback period in detail, consider a 1.5KW solar setup in three different cities of Australia. This will give you a general idea about the payback period of a solar charging station.
For this, we assume the energy consumption of 25KWh/day at 25c, and our system is operated at 85% efficiency. We also assume two cases of consuming either 70% or 100% of the energy produced by the solar setup.
City 
Cost of Installation in Dollar (AU) 
Energy Consumption 
Payback Period in Years 
Annual Savings in Dollars (AU) 
Sydney 
3200 
70% 
6.1 
500 


100% 
4.9 
640 
Melbourne 
3300 
70% 
6.5 
480 


100% 
5.2 
610 
Brisbane 
2900 
70% 
5.2 
540 


100% 
4.1 
690 
How Many Solar Panels To Charge Popular Makes Of Electric Cars?
The following table gives you some idea of the number of solar panels need to charge the most popular makes of EV and assumes an average commute of 30 miles/day.
Car 
Battery Capacity 
Number of 250 watt solar panels needed 
Tesla Model 3 
82

8

Tesla Model s 
85 
6 
Chevrolet Volt 
18.5 
9 
Nissan Leaf 
64 
7 
Tesla Model X 
90 
6 
Ford Fusion Energi 
9 
9 
BMW i3 
42.2 
6 
Related Questions
How many solar panels to charge a Tesla?
The Tesla Model 3 would require 8 solar panels of power rating 250 watts to charge it assuming an average mileage commute of 30 miles/day. The Tesla Model S would require 6 solar panels – energy requirements depend on battery capacity and range.
How many solar panels to charge a Chevy Bolt?
The Chevy Bolt would require 9 solar panels of power rating 250 watts to charge it assuming an average mileage commute of 30 miles/day.
How many solar panels to charge BMW i3
The BMW i3 would require 6 solar panels of power rating 250 watts to charge it assuming an average mileage commute of 30 miles/day.