# How Many Solar Panels To Charge A Tesla?

Updated on November 13, 2022

How many solar panels does it take to charge a Tesla?

## Can you charge a tesla with solar panels?

In general, anything with a battery can be charged up using solar panels, if you have enough of them.

#### Discover your solar saving potential

When sizing solar power systems, the load drives everything. The first step is to find out how much energy the solar panels need to generate to replace the energy discharged from the battery.

As a general rule, 10 solar panels rated at 300 watts each will be required to charge a Tesla electric vehicle if the daily mileage was around 30 miles, which is the average commute distance in the USA. The energy needed is about 6kWh, representing about 6.5% of A Tesla S 85kWh battery.

## How big is the battery in a Tesla?

Tesla batteries have evolved over the years – the table below gives some idea of the current status of some Tesla EV models:

### Table: Tesla Models With Battery Sizes And Range

 Model Battery Size (kWh) Range (miles) Battery Weight (pounds) Number of cells S 85 402 1200 7104 3 50/82 220/353 1054 4416 X 100 348 1200 Roadster 100 244 1836 Cybertruck 120 460 Y 80 244
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## How far does the average person commute to work?

It isn’t realistic to use the full battery capacity as the energy required to charge a Tesla with solar panels. For some models it would be around 100kWh, which is a huge amount.

To put it in perspective, the average energy consumption of a US home is around 90kWh/month. We shouldn’t assume that a Tesla battery will ever be completely discharged – this is not what happens in real-life situations.

Studies show that the average American commutes just 30 miles a day. Using the Tesla model S as an example, with a range of 402 miles, then 30 miles represents about 6.5% of the full battery capacity.

Let’s double this to play safe and use a 60 miles commute, which is 13% of a Tesla Model S battery capacity of 85kWh, or 11kWh.

The solar panel array used to charge a Model S should be sized to supply 11kWh.

## How long would it take to charge a tesla with solar panels?

The best solar option is to use an inverter to power the normal Tesla charger. In this case the charging time would be the same as the regular charger time, if the solar panel array is correctly sized.

Using a home charger, a Tesla would be charged in a day.

Two important factors to consider when sizing solar panels is the size of the individual panels and the irradiance in your geographic location.

While there are several factors affecting solar system output, irradiance (the sun’s energy) in kWh/m2/day is by far the most important.

It’s also called peak-sun-hours and is used by solar installers to estimate solar panel array size.

Irradiance is found by consulting historic database values such as this is found on the site GlobalAtlasInfo – see the image below:

How long to charge a Tesla with solar in Texas?

The image shows the irradiance for Houston, Tx as 1552 peak-sun-hours per year, which equals 4.25 peak-sun-hours per day. I’ll use this value for our calculation.

Note: Don’t imagine that you can connect solar panels directly to the Tesla battery to charge them up. It seems to make sense, but this isn’t how it works.

The safest way is to use an inverter and plug in the regular charger. There  will be losses associated with the inverter, but these will be minimal if it is sized properly i.e. about the same rating as the solar panel array in watts.

Solar power required = 11kWh (for 60 miles commute)/4.25 peak-sun-hours = 2588 watts

Number of solar panels required = 2588/300 = 8.62 (9) solar panels 300 watts each

Note: In practice, solar power system rating should be multiplied by 1.44 to account for the losses associated with a working system.

In this case, for a 60 mile commute, the 13 solar panels each rated at 300 watts would be required , which equates to a power rating of 3900 watts.

### Solar ev charging station cost

The approximate cost breakdown for this solar power system is as follows:

• Solar panel array: \$11000
• Solar nverter: \$5000
• Solar Charge Controller: \$500
• Wires and cables: \$300
• Other expenses: \$200
• Total cost: \$17000

## Can you charge a tesla with portable solar panels

I’m a great fan of portable solar panels and the flexible folding type are a great buy. I have an 80 watt dokio portable (see image below) which is extremely reliable and is very efficient.

Dokio solar cells are quite unique and boast 25% efficiency. It’s invaluable for popping in the car to use for camping or similar outdoor activities. Great for battery charging!

Renogy have a great range of folding suitcase-type solar kits, such as this 300 watt model.

If your commute is particularly light, then you could feed an inverter with one of these to charge your battery while the car is parked at work, for example.

As a permanent option, for daily recharging, it isn’t really a viable option.

I favor a more permanent option, like installing fixed panels onto an outdoor structure, such as creating a solar pergola, where the car is parked regularly at home.

## How many solar panels does it take to charge a Tesla overnight?

Solar panels can’t store electricity so a battery bank will be needed to charge at night. The size of the battery energy storage system can be calculated using the value of battery discharge in kWh.

In the case of a 60 mile commute for a Tesla S, this is 11kWh

Energy required = 11kWh/charging time (say 8 hours)  = 11000/8 = 1375Ah

Number of batteries required = 1375/200 = 6.87 (7) batteries each 200Ah

Cost of batteries approximately \$3000

## What happens if your Tesla runs out of charge?

As you approach the end of battery life, you’ll get a warning “Battery power very low. Heating and A/C reduced.” If you keep going, another warning will appear “Car shutting down, pull over safely.

A little while afterwards, you’ll hear an alarm and the car will lose power.

Some models can be towed and some can’t, so the best option is to have the car loaded onto a flat-bed truck to either go home or to a charging station.

Roadside associations are exploring roadside emergency chargers on their vehicles, and it seems these will become more common as the numbers of EVs increase.

Technically, it isn’t good for any batteries to be completely discharged, even the lithium type used in electric vehicles. A good rule is to discharge to 80% maximum in order to maintain long battery life.

## How many solar panels to charge a Tesla Powerwall 2

Tesla Powerwall 2 energy storage has a capacity of 14kWh. Let’s assume that it is completely discharged (not normal) and needs to be fully recharged with solar.

Using the average US irradiance value of 4 peak-sun-hours, then the calculation is as follows:

Solar energy required = 14000/4 = 3500 watts (3.5kW)

Number of solar panels = 3500/300 = 11.66 (12) panels, each 300 watts

Note: To take into account solar system losses, the power rating should be multiplied by 1.44. In this case, the number of solar panels required will be 17 panels, each rated at 300 watts.