Can I Charge a Tesla With a Portable Solar Panel?

No. The a Tesla automobile’s battery has a huge capacity relative to the output of a single solar panel, and the voltage and current type do not match.

Charging an EV with Solar Power

We recently had a client ask if they could charge a Tesla with a portable solar panel. It’s an interesting question with a pretty simple answer – no. The question just goes to show how little is know by the general public about how much energy it takes to run an electric vehicle, how much capacity a Tesla battery has, and its relation to solar power production capability.

How Much Power Does the Sun Produce on Earth?

On a sunny day under the sun will cast about 1,000 watts per square meter on the earth’s surface when the sun is directly overhead. If you could make a perfect solar collector that absorbs and converts 100% of the sun’s energy, in one square meter you could produce 1,000W under ideal conditions. That assumes the sun is directly overhead, and of course the sun moves relative to any point on earth.

The sun is rarely directly overhead. Clouds, haze, and other environmental factors reduce the actual power available at the earth’s surface. In reality, each square meter on a given day receives about 5,000 watt-hours in Southwest Florida.

Doing the Math

Consider a fully depleted 90 kilowatt-hour (90,000 watt-hour) Tesla battery. It would take 18 days to charge up with a perfectly efficient solar panel measuring 1 square meter (10.8 square feet).

However, typical commercially available solar photovoltaic panels are only about 18% efficient today. That means you only get about 900 watt-hours per day of energy output in a square meter. That would require 100 days to charge up your Tesla.

A common solar panel size that you see on homes with solar electricity is about 1.6 square meters. At 285 rated watts, it produces about 1,425 watt-hours per day, meaning that solar panel would take 63 days to charge up a fully depleted Tesla 90kWh battery.

And these figures represent a perfectly efficient system, where there are no losses in charging the battery or in the system wiring. In reality, some energy is lost as heat during the charging process.

Other Factors

Solar panels produce DC electricity. DC current is required to charge Tesla batteries, but the charging port is designed to accept AC electricity. In theory a direct DC charging capability could be added to the automobile, but then the voltage would be mismatched. There are lots of complications in doing this.

To make it work today you would need to convert DC to AC first, and the Tesla would convert from AC back to DC. This adds more inefficiency to the charging system.

Can a Single Solar Panel Charge a Tesla?

It is impractical to charge a Tesla with a single solar panel, which is why you don’t see EVs being built with solar roofs (which would essentially be nothing more than a gimmick). There simply is not enough output from a single solar panel to make a dent in energy use for a moving automobile today.

To be sure, a solar panel could keep the car cooler, keep some electronics working, and keep the battery topped off for long periods between use. That might be a practical way to incorporate a solar panel into the car or to use a portable solar panel effectively.

Note: I know, automobiles with solar panels in the roof have been done… Gimmick IMHO.

Can My Home Solar Electric System Charge My Tesla

Absolutely! In fact, installing a grid-interactive solar panel system comprised of many solar panels is the easiest way to offset the energy used by your Tesla or other EV.

A grid-interactive photovoltaic system simply works in concert with the utility grid to supply your home with electricity. This includes the electricity required to charge your Tesla. Excess energy produced is sold back to the utility grid. Energy shortfalls are made up by your buying electricity like normal.

If you want to charge your Tesla with solar panels, this is the most effective way to do that today. Because an EV will increase your electric bill, you can use solar panels to offset or eliminate the difference. In fact, you could make your home energy neutral if you have the roof space and budget.

Conclusion

It is impractical to charge a Tesla with a portable solar panel. The amount of energy needed for an electric vehicle far exceeds the energy production of a single panel. A complete solar energy system can be used to offset the need for utility electricity to charge your Tesla.