How Many Solar Panels to Charge an Electric Car?

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Electric cars and portable solar panels certainly seem to be the perfect combination. With renewable energy costs going down fast, doesn’t it make sense to pair the two? As we will show here, it is more than possible to power electric cars with solar panels ,though the number required depends on several factors.

if you drive 25 miles a day and the car battery has a 40kwh capacity, you need 6.6 kwh of solar power. Five 300 watt solar panels can produce 7.5kwh a day so that is sufficient.

How Many Solar Panels Does an Electric Car Need?

Electric car batteries have different capacities. We are using the Nissan Leaf as an example which has a 40kwh capacity. However you can use process given here, just replace the 40kwh with whatever specifications your car has.

The calculation is Car battery capacity x miles you drive per day / mileage

The Nisan Leaf has a 40kwh battery and a mileage of 1kwh per 3.7 miles or 40kwh / 150 miles. Studies show Americans drive 30 miles a day, but electric car owners drive less, around 23-25 miles. So let us go with 25 miles here. Using the formula above:

40 x 25 / 150 = 6.6kwh

A 25 mile drive uses up to 6.6kwh. So now we just need a solar array that can produce 6.5kwh or 6500 watts per day to charge the car battery. And as we showed earlier, 6 x 300W solar panels is enough.

Assuming a 300 watt solar panel produces 300 watts an hour, it can give you 1500 watts a day with 5 sunlight hours. With five of thee you get 7.5kwh.

With this procedure you can calculate how many solar panels any electric car will need. There is a more powerful Nisan Leaf equipped with a 62kh battery for instance. The Audi e-Tron has a 95kwh battery and the Tesla 5 has a 100kwh capacity, and these cars are getting more powerful all the time.

if you have an e-Tron for instance, its 95kwh battery means you have more than 200 miles mileage with a fully charged battery. Yes it would take longer to power up, but you can recharge it when the capacity drops to 50% like a lead acid battery.

The large the car battery capacity, the longer you can drive the car. But it also means a longer charging time. However it is unlikely you will fully discharge the battery. If you only drive 25 miles a day and the car has a 150 mile capacity, you can count days between charges.

How Many Solar Panels are Needed to Charge the Top Electric Cars?

The table lists some of the most popular electric car models available and their battery capacity. The calculations are based on a 25 mile a day drive. Adjust the calculations based on how many miles you drive.

These are just estimates based on the model mileage. The actual number of solar panels you will depends on many factors. Aside from your driving range, you also have to account for the weather in your area.

In the calculations here for instance, we base it on the assumption the solar panel generates 300 watts an hour with 5 sun hours available. The rating and output of a solar panel can vary because of environmental factors.

During summer you can expect solar panels to produce more power, so charging batteries will go faster. During winter there is less sunlight available so charging is going to be longer.

Your location also plays a part. Some parts in the US such as the West and Midwest receive more sun than the Northeast. So even if it was summer in both locations , the output will be higher in places where there is more sun.

The bottom line is you need to consider several factors when it comes to charging electric cars. Is it possible? Yes, but you have to realistic with the charge time expectations especially during cold season.

Can You Install a Solar Panel on an Electric Car?

We have shown that you can charge electric car batteries with solar panels .But can you charge a car directly with solar panels? For instance, can you mount solar panels on a car so it will run using solar power?

You can charge an electric car with 8 to 12 solar panels. But it is not practical because these are too heavy for the car and there is not enough space available. It is more effective to use solar panels to charge the car battery

An electric car uses approximately 30 kwh per 100miles. Of course some cars are more efficient than others, but we are using this figure for a simplified computation.

30 miles is about 10 kwh or 1000 watts. So you need 8 to 12 x 250W solar panels to run a car 30 miles a day. Five 250W solar panels can produce 1000W if each generates 1kwh daily. But we recommend going with 12 to account for energy loss and fluctuations in sunlight intensity.

So theoretically it is possible. But practically it is difficult for the following reasons.

• You need near perfect conditions to produce 8kwh from the panels. If there is a sudden downpour or turns overcast, it might be impossible to reach this level. The car will slow or suddenly stop.
• Solar panel production drops during winter. But if you charge the battery with solar power, you can drive regardless of the weather.
• There’s no way to put 8 to 12 solar panels on an electric car. Each one is about 5.5 feet long and 40 lbs. each.
• Flexible solar panels are not as efficient as rigid PV modules. They are portable, but it comes at the expense of efficiency. It is not a big deal if you are charging a mobile device, but with a car it is.
• Solar panels weigh too much and will put undue pressure on the car roof. And driving around the city means the panels will be blocked by buildings and other structures.

The scenario above also assumes you drive only 30 miles a day. What if you are going on a long road trip or your job requires traveling from state to state? You will need two dozen solar panels or more to charge a 40kwh battery.

There are too many drawbacks to installing solar panel on electric car. Until we can reduce the panel size, it is better to charge the battery instead.

Reminders For Charging an Electric Car with Solar Panels

Calculate how many miles you drive per day. We use the national average in our examples, but yours might be higher or lower. Use your own number to figure out how many solar panels will be needed and how long the charge can take.

Keep in mind that electric cars have different battery capacities and mileages. While the Nissan Leaf has a 40kwh/150 mile mileage, other cars have higher or lower specifications. This affects the battery charge time and the number of solar panels you have to use.

The other thing is something we already mentioned, but bears repeating. Solar panel watt ratings do not imply they produce that amount all the time. A 300 watt solar panel can reach 300 watts in ideal weather. That is when the sun is shining brightly. During cloudy days and late afternoon, solar power production drops as the sun sets.

So in our calculations we have a 5 x 300 watt soar array producing 75.kw or 7500 watts. This is possible if all the panels generate 300 watts for 5 hours. But if output falls below 300 watts, they might not reach 7500 watts.

But if there are more than 5 hours of sun, that drop in output will be compensated for by the extra hours. So there are a lot of variables you have to factor in. But this is not as difficult as it seems because all solar systems have a status indicator so you can tell how well it is performing.

Conclusion

Charging electric cars with solar panels is feasible and practical. With solar panel costs going down and efficiency going up, it should not be long before we see electric cars use this method more often.