How Many Solar Panels To Charge A Tesla?

How Many Solar Panels To Charge A Tesla

Wow! Have you ever considered using solar panels to recharge a Tesla?

Tesla solar chargers would be the best thing you can do to save the environment without compromising on your luxury.

But can you really use a solar panel to charge Tesla?

Theoretically, you can. As long as you have a sufficient number of solar panels, you would be able to charge any battery for that matter, including a Tesla.

Read on to learn more about Tesla solar chargers.

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    Is it possible to charge Tesla using solar panels?

    When you are planning to replace grid energy with solar powered tesla charger, you need to know the load requirement. This is the rate of discharge of the battery. A solar system needs to have the capacity to compensate for the discharged energy at the same rate.

    To calculate the number of solar panels needed for Tesla solar chargers, we need to know the distance traveled daily. We also need to assume certain basic parameters such as hours of peak sunlight to help with the calculation. You may change these figures as per requirement and location.

    Here, for the sake of calculation, we are considering 300-watt solar panels. The average daily commute is taken as 30 miles. For a Tesla Model S with an 85kWh battery, the daily energy requirement would be approximately 6.5kWh. 

    Let’s understand the calculation in detail.

    Tesla models, battery capacity, and range

    Tesla has many models with varying battery capacities and ranges. This table will give a better understanding of the size and performance of Tesla batteries across models.

    Model Battery Capacity (in kWh) Range
    Model S 85 405
    Model 3 54/62/75/82 220/262/353/313
    Model X 100 305/325
    Model Y 75 303/326/224
    Roadster 53/200 393/620

    What is the average distance of commute in the U.S.?

    Even for the sake of calculation, it is not realistic to charge the full capacity of a Tesla battery using solar panels. While this can be as low as 50kWh for a Model 3, it can go up to 100kWh for Model X. For the calculations here, let’s use the Model S with an 85kWh battery.

    Charging the entire 85kWh using solar panels is unrealistic. Typically, in the real world, we never wait for a battery to fully discharge before recharging it. So, let’s consider daily energy consumption. To calculate this, we need to know the average distance traveled by a person. 

    Various studies indicate that on average, the commute to work in the U.S. is 30 miles in a day. Let’s go a bit beyond this and make the calculations for a daily mileage of 50 miles. 

    As we are taking the Tesla S for the calculations here, its range is 405 miles. 50 miles represents approximately 12.5% of 405 miles. Applying this percentage to the battery capacity of 85kWh, we get 10.625kWh. Let’s round it off as 11kWh. 

    So, 11kWh is the daily energy discharge of the battery. We need to figure out the number of solar panels required to supply 11kWh of energy to recharge the Tesla Model S battery.

    Time needed for charging a Tesla using solar panels

    Even though it may be inconceivable that a Tesla cannot be charged directly using solar panels, this is a simple truth. There is no provision to plug the battery directly into the solar panels. Moreover, it is safer to direct the energy generated through a charge controller to prevent overcharging and resultant damage.

    The best practice would be to route the energy through an inverter and use the standard charger. When you are charging a Tesla battery using an inverter, the time required for charging would be equal to when using grid energy. However, for this, it is important to have a solar array of optimal size.

    You need a day to recharge a Tesla battery at home.

    When we mention the optimal size for the solar array, it includes the specifications of individual panels as well as the availability of sunlight in your location, also known as irradiance or peak sun hour.

    You can find out the irradiance of your location from GlobalAtlasInfo. You will find this against “Direct normal irradiation”. It is given as kW/㎡/day. This figure denotes the number of hours of peak sunlight received by the location. For instance, for California, this comes to 6.469kW/㎡/day.

    When you are using an inverter in the process, you also need to account for the loss of energy associated with it. You can minimize energy loss by using the right-sized inverter for the solar panels.

    The daily energy requirement is 11kWh. 

    Dividing it by irradiance, we get, 11kWh/6.469kW/㎡ = 1.70kW

    Solar panels (300 watts each) required = 1700/300 = 5.67

    Rounding off, we get the number of 300-watt solar panels as 6. 

    Note: In a solar energy system, as in any electric circuit, there will be a loss of energy on various counts. This energy loss needs to be accounted for while calculating the number of panels. We need to multiply this number by 1.44. This will give us the real figure.

    6 x 1.44 = 8.64

    This means, for a daily 50-mile commute in a Tesla Model S, you need to have 9 300-watt solar panels to recharge the battery. Don’t forget that this is for California. If your location is different, you need to make the calculations using the irradiance there.

    How much will the solar system cost?

    The estimated costs of various components of a solar energy system are:

    Solar array – $8310 (before tax incentive)

    Inverter – $5,000

    MPPT charge controller – $400-600 (average $500)

    Connectors and cables – $200-300 (average $250)

    Installation charges – $200

    Total – $14260

    Is it possible to charge Tesla using portable panels?

    When you are on the road, you need to have a feasible choice for charging a Tesla using solar panels. Will a portable Tesla solar charger do the job?

    Yes, they work equally well. The challenge is to have enough portable solar panels to meet the need. 

    This 300-watt portable model from Renogy is a good choice. Renogy offers a variety of easy-to-carry suitcase models for portable energy needs. 

    You can manage to recharge a Tesla battery with portable panels if you are traveling short distances and the halt is long enough during the daytime. For example, the commute to your nearby workplace. 

    However, portable Tesla solar chargers will not be enough for long-distance commutes or as an everyday option. For your daily recharging needs, you need to use regular fixed Tesla solar chargers. You may consider building solar pergola for parking the car and recharging it using solar energy.

    How to ensure Tesla is charged overnight?

    Nighttime charging will require a battery to store the solar energy generated during the day. To calculate the required battery capacity, all you need to do is estimate the discharge value of the battery. That is how much energy you are using up every day. 

    As per our assumptions earlier, for a 50-mile commute on a Tesla Model S, the energy used up is around 11kWh. Here, we take the time taken for recharge as overnight or 8 hours. 

    Energy required for recharge = 11kWh/time taken for charging = 11000Wh/8hours 

    = 1375Ah

    For batteries of 200Ah each, the number required = 1375Ah/200Ah = 6.875

    The battery cost for Tesla solar chargers will come to around $2500-3000.

    What to do when a Tesla battery is fully drained?

    This is an eventuality you need to be prepared for but try to avoid it by recharging regularly. However, even if you are not following the battery recharging protocol, there is no need to worry. The battery will warn you sufficiently early as the charge crosses a minimum threshold. 

    The green indicator of the battery will turn amber when the battery charge touches 20%. You’ll also receive a warning – “Low battery. A/C and Heating reduced”

    In case you continue to drive despite the warning, you will receive the next warning – “Car is shutting down, safely pull over.”

    After this warning, an alarm will go off and the Tesla will shut down completely.

    Once a Tesla shuts down and loses power, the only thing you can do is to get it towed or load it on a flatbed truck and take it for charging.

    It is not recommended to allow any battery to discharge fully, including the lithium-ion batteries used in EVs. To get the best out of your batteries and prolong their lifespan, recharge them after a maximum of 80% discharge.

    Number of solar panels required to charge Tesla Powerwall2?

    The capacity of a Tesla Powerwall2 is 13.5kWh. It may be fully or partially discharged at the time of recharging. Let’s imagine that the battery is fully discharged for the sake of calculations here. 

    To figure out the number of solar panels required for this, the calculations are:

    The average irradiance in the US is 4 hours of peak sunlight. 

    Solar energy needed = 13.5kWh/4 = 13500Wh/4 = 3375watts = 3.375kW

    Solar panels needed (300watt/panel) = 3375/300 = 11.25

    That is, 12 solar panels of 300 watts each are required to recharge a fully discharged Tesla Powerwall 2.

    Note: To compensate for the power loss, we need to multiply this by 1.44. This means 17 solar panels are needed to do this job.

    Bottom line

    The bottom line of a Tesla or for that matter any EV is avoiding the use of fossil fuels. As most of the grid energy is generated from thermal power plants, charging a Tesla using grid energy defeats its fundamental purpose. 

    Charging a Tesla using solar panels is the best thing you can do to save the environment.

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