[EV Series] Part 1: Charging your EV from your own Solar Energy

[EV Series] Part 1: Charging your EV from your own Solar Energy

[EV Series] Part 1: Charging your EV from your own Solar Energy

We’ve all been there. The sign on the side of the road says “last gas for 100 miles” and our empty light has just come on. Better pull over. Filling up on gas is ingrained in our society but with electric vehicles beginning to take over the market, how will our habits change behind the wheel?

Solar and EVs are a perfect pair, so we are invested in keeping our clients in the know about both technologies. This will be an ongoing series covering all sorts of topics related to EV charging. This is a broad topic, so we’ll start close to home, (as many new EV drivers will) and focus on how solar at your home can integrate with your EV. We’ll explore the basics of home charging equipment, and how you can use your solar panels to drive on the power of the sun!

There are two basic options for home charging. You can drive your new EV home and plug it straight into a standard 110-volt outlet on your wall, just as you would a microwave or cell phone charger. It works, but your vehicle’s usability will be limited by long charge times. You’ll be able to add about 5 miles of range per hour, or 60 miles in 12 hours.

Level 2 charging makes use of a 240-volt outlet. This is similar to what you’d have on a washing machine or dryer. Some vehicles will come with an adapter for this type of plug that you can carry with you. In other cases, you’ll need to purchase a charger that plugs into this outlet, then into your car. This will get you around 20-30 miles of range per hour, or 240-360 miles in 12 hours. Solterra can install this outlet for you so you’ll be ready for your existing or future EV.

Click the image for more on charging levels from Forth Mobility.

I have my car and my charger. How much solar do I need to power my EV?

Folks have different driving habits, just as different households and businesses will have widely variable electrical consumption over the course of a year. When we are designing a solar system for your home, we look at your annual electrical usage. If 20 panels is all you need to cover your consumption, there’s no benefit to putting up 30 panels. But how much will an EV add to your consumption? If you’ve already owned and charged your car at home for a year, that data will be included in your bill history, and we can size the system based on that. If it has been less than a year or no time at all, we can estimate based on how many annual miles you will drive and on the EV’s range and battery specs. Talk to your solar design consultant about how you plan to utilize your EV and they will size your solar accordingly.

Just like gas cars, the type of vehicle, and your driving habits will impact how far you can drive before refueling. You’ve likely seen vehicles get between 20 to 40 miles per gallon. Since a battery doesn’t have gallons, the metric we use is miles per kilowatt-hour (mi/kWh). EVs will typically get 3-5 mi/kWh. Your EV also will have an EPA estimated range per charge. We find that the average driver will get 80%-90% of that range.

See more on this from J.D. Power.

Photo by Orau on Pexels

Some basic math to put that in perspective, driving 1000 miles in an EV will use 200-330 kWh.

If you drive 10,000 miles in a year you’re using between 2000 and 3300 kWh/year to drive.

Let’s run a couple of examples. For our calculations and for solar sizing, we will assume 90% of EPA range is achieved.

Example 1 – 2022 Chevy Bolt, Annual driving 10,000 miles

  • Battery Size – 65 kWh, EPA Range – 259 Miles
  • Real World Range – 259*90% = 233 Miles per charge
  • Charges per year – 10,000 annual miles / 233 miles per charge = 43 Charges needed
  • kWh per year – 43 Charges * 65 kWh per charge (battery size) = 2,795 kWh needed per year

Example 2 – 2021 Tesla Model 3 Performance, Annual driving 10,000 miles

  • Battery Size – 82 kWh EPA Range – 353 miles
  • Real World Range – 353*90% = 318 Miles per charge
  • Charges per year – 10,000 annual miles / 318 miles per charge = 32 Charges needed
  • kWh per year – 32 Charges * 82 kWh per charge (battery size) = 2,624 kWh needed per year

If your home uses an average of 12,000 kWh per year, an EV could increase your electric demand by 20%-25%. The good news is that it only takes 7-10 solar panels to cover 100% of your driving needs! If you drive fewer miles, it will take fewer panels and vice versa.

Our objective as solar design consultants is to put all this information in perspective with regard to your goals and build a solar and EV charging solution customized to you. Reach out to get the conversation started. Check back soon for the next part of this series, and see more EV news here!

If you are interested in learning more about how solar can power your EV, get a free quote here, email us at [email protected], or call or text 206-462-1103.

Author Bio:




Isaac Chamberlain (he/him) is a Solar Design Consultant at Solterra Solar. He is passionate about solar energy, electric vehicles, and how they can work together to move us toward a sustainable energy system. When he’s not driving his electric car to solar consultations, he cruises the streets of Seattle on his electric motorbike or finds trails to ride on his mountain bike. He also coaches high school ultimate frisbee and enjoys vegetarian burgers and baking sweet treats to share with office mates! 

No Comments

Post a Comment

Get an instant ballpark solar estimate using satellites!