Are solar-powered cars possible? Absolutely — but it may not be what you’re picturing.
According to the National Renewable Energy Laboratory (NREL) roughly 25% of American Electric Vehicle (EV) owners also have solar at home. If you’re in the market for an EV or recently purchased one you might also be considering whether solar is right for you. So why have so many homeowners invested in EVs and home solar?
Well, let’s run the math.
Car Fuel Math: Gas vs Electric
If the average car gets 25 mpg and the average cost of gas is $3.50/gallon, that means the fuel cost per mile for the average internal combustion engine car is 14 cents per mile. Doesn’t seem like a lot but it adds up to $50 or more every time you fill your car up at the pump.
How much does it cost to charge an EV at home with solar? The math is a bit different. The average EV gets 3 to 4 miles per kilowatt hour (kWh). We know from our solar experience that the average home can amortize out the investment in solar to about 8 cents per kWh, which means your “fuel” expense is around 2 cents per mile — a fraction of paying at the pump.
For the average American driving 14,000 miles per year, that adds up to nearly $1,700 in annual fuel cost savings. These savings are likely to increase each year as the cost of gasoline rises.
| Fuel Source | Fuel Cost per Mile | Annual Fuel Cost |
| Gas Pump | 14 cents | $1,960 |
| Home Solar | 2 cents | $280 |
But not everyone has solar, which means they charge their car at home by purchasing power from their utility. Utility rates vary dramatically by location, and even time of day in some areas, but if you’re paying more than 24 cents per kWh then you’re about cost-neutral with buying gas at the pump.
And homeowners feel this. The average utility bill goes up 40% after buying an EV because of the increased consumption in charging their car. While EVs offer benefits over ICE vehicles, most homeowners might find they’re simply shifting their fuel costs from the pump to their electric utility without investing in home electrification.
Why Don’t We Put Solar Panels on Top of Cars?
The simple answer is space constraints. It takes between 5-12 solar panels to fully power an EV, depending on how much you drive and your sun exposure. So, instead of putting panels on cars, more and more EV drivers are installing solar panels and EV charging at their homes to create their own personal solar-powered EV charging stations.
Together, rooftop solar and EV charging make a dynamic duo. In addition to the fuel cost savings outlined above, advantages include:
- Locking in a flat cost for solar power to hedge against rising utility rates
- Powering your EV with clean solar electricity
- Charging your car during power outages (with sufficient battery storage)
- Increasing the value and appeal of your home
Solar-powered EV charging is also a massive step toward energy independence. You own the charging station and the fuel!
Considerations for Solar-powered EV Charging
Solar.com Energy Advisors will almost always size a solar array based on current electricity usage. However, if you’re considering purchasing an EV, then it’s recommended to over-size the array to the limit your local utility allows. This will help lock in that low value of solar versus being subjected to utility rate increases.
Because many roofs are space-constrained, investing in higher-efficiency solar panels with a high-performance inverter might make the most sense to squeeze the most value out of your roof.
Once you have your EV charger installed and your solar array operational, the final step to optimize savings is to set your home charger settings around optimal times based on your value of power relative to your usage. Especially if you’re in a Time of Use rate area charging your EV right when you get home in the evening may be a very expensive way to top off your battery. Almost every EV charging app has smart charge controlling settings to automatically charge your car when the value of electricity goes down and some will even communicate with your solar array to optimize charging coincidental with high solar production.
Ready to explore how to save money charging your EV with solar? Connect with a Solar.com Energy Advisor to get your complimentary solar design.
