Cost of charging an electric car (and how solar can help)

One of the big selling points of electric vehicles is that they cost less to operate than gas-powered cars.

This is usually true: with no oil changes, fewer mechanical systems that can fail, and even less wear on brake pads (due to regenerative braking), electric vehicles are generally cheaper to operate.

The story is the same when it comes to fuel costs. In most cases, you’ll pay less for electricity to charge an electric vehicle than you would to keep an internal combustion engine (ICE) vehicle fueled with gasoline. However, this sometimes isn’t the case, particularly when you live in a state like California with high electricity prices and you mainly charge during utility peak hours.

Solar panels can dramatically reduce or eliminate the impact of adding an EV to your home. To help understand this, let’s use a Tesla Model Y (the best selling EV in 2022) as an example.

How much does it cost to fully charge an electric vehicle?

The battery capacity of the rear wheel drive version of the Tesla Model Y is 75 kilowatt-hours (kWh). This means if you start from a completely drained battery and charge it to 100%, you would need at least 75 kWh of electricity. However, charging isn’t 100% efficient: some electricity is lost as heat in the wiring and AC-to-DC power conversion. According to Car and Driver, charging a Model Y is about 87% efficient on average. This means that if your home charger uses 100 kWh of electricity, only about 87 kWh of that will end up getting stored in the car battery.

After accounting for charging losses, you will use 86.2 kWh of electricity to charge a Tesla Model Y to 100% from empty. According to the EIA, the average price of electricity in the US is 15.64 cents per kWh.

That works out to $13.48 to fully charge a Tesla Model Y. Its EPA range is 244 miles, so you would pay on average 5.5 cents to drive one mile.

How much does it cost to charge a Tesla in California?

15.6 cents per kWh the national average price of electricity, but that would be considered a bargain in California.

How much does electricity cost in California? PG&E is the largest utility company, so let’s use them as an example.

A common PG&E rate plan for homeowners is E-TOU-C, which is a tiered rate plan with peak hours from 4 p.m. to 9 p.m. every day. Tiered means that the price changes if your monthly usage goes above a predetermined baseline. In addition, there are different rates during summer and winter and time of day.

This makes calculating the cost of charging an EV a little bit complicated. Here’s a table that summarizes the cost of charging our Tesla Model Y at different times.

While we used the Model Y as an example, other popular EVs such as the Ford Mustang Mach-E, Hyundai Ioniq 5, and the VW ID.4 have similar battery sizes.

As you can see, the price of charging your EV in California with PG&E will vary significantly, from as low as $25 during winter off-peak to a high of $42.24 if you charge during on-peak hours and your household usage pushes you over the baseline.

However, PG&E - like other utilities in California - has a special rate for EV owners. It also happens that these EV rates are also required by California’s coming NEM 3.0 rules, which stipulate that solar homeowners will need to adopt rate plans that have the greatest price differential between summer off-peak and on-peak times. The EV rate plans, which encourage people to charge their vehicles when demand on the grid is low, meet this criteria.

PG&E’s rate for electric vehicles and NEM 3.0 customers is E-ELEC. Let’s see how it compares:

As you can see, the E-ELEC rate results in a lower cost to charge your EV during off-peak hours in both winter and summer, but a higher cost if you use on-peak. This is exactly what this rate was designed to do.

How much does it cost to charge a Tesla in Texas?

California has some of the highest electricity rates in the country, especially when it comes to peak rates. Texas, on the other hand, has much cheaper electricity, and TOU rates aren’t required.

Texas has a deregulated electricity market, and homeowners can choose from a large number of electricity suppliers. I took a look at the Power to Choose website and found that a customer in Houston can pay approximately 10 cents/kWh.

This means to charge a Tesla Model Y - or other EV with a battery about 75 kWh in size - will cost around $8.62. That translates to a driving cost of 3.5 cents. That’s a lot cheaper than California!

How does the cost of driving an electric vehicle compare to an internal combustion engine?

One of the big selling points of electric vehicles is saving money on fuel, so let’s see how these charging costs compare to fueling a comparable gas vehicle.

The Tesla Model Y is a luxury compact SUV. I’m not a car expert, so to find a comparable gas vehicle I checked with Motortrend and found that they rated the Genesis GV70 as the best luxury crossover of 2022. According to the EPA, the Genesis GV70 has a fuel economy of 24 mpg or 4.2 gallons per 100 miles.

I looked up today’s average price of gasoline on Gas Buddy and found that gas in California and Texas costs $4.53/gallon and $2.99/gallon, respectively.

Based on that, we can compare the cost of driving these two vehicles:

As you can see, even if you charge your car in the summer during California’s utility peak rates, a Tesla Model Y is still slightly cheaper to drive than a comparable gas-powered vehicle. If you charge your vehicle at night or live in a place such as Texas that has cheap electricity, the EV is the clear winner.

How about other electric vehicles?

I used the Tesla Model Y for these examples because it’s currently the most popular EV on the market, but there are many others available on the market. The Model Y happens to be more of the most efficient EVs, so a different vehicle may cost you more in electricity costs.

For example, while the base trim Model Y achieves 129 MPGe, the Chevy Bolt has a lower fuel economy of 120 MPGe, even though the Bolt is a subcompact.

To do the price calculations above for your own vehicle, you can look up their fuel efficiency at fueleconomy.gov.

How does solar make it cheaper to charge your electric vehicle?

If solar panels are feasible for your home, then you can reduce the cost of charging your vehicle. Start by calculating how much electricity your annual driving consumes. That will tell you how many solar panels you need to add to your system to offset your driving.

Look up your vehicle’s EPA fuel economy, or use the actual fuel economy recorded by your vehicle. For example, the Tesla Model Y has a fuel economy of 26 kWh per 100 miles. That’s 260 kWh per 1,000 miles, or 2,600 kWh per 10,000 miles.

The average person drives about 14,000 miles per year, which works out to 3,640 kWh consumed annually if you have a Model Y. But remember that charging is perhaps only 87% efficient, so divide that number by 0.87 to arrive at a final number of 4,184 kWh.

Do the calculation for your vehicle, then add that amount to your household’s total electricity usage. That will tell a solar installer how large your solar array needs to be to generate 100% of your electricity needs from solar power. You can also use the Solar Nerd calculator to quickly get a ballpark figure.

Of course, you don’t have to generate 100% of your home’s electricity with solar. Since I originally installed my solar panels, I’ve added an EV and a heat pump, so now I’m generating only about half of my usage from solar. Even so, it’s worth it because my utility bills are a lot lower than what they would be without solar panels.

Bottom line: solar panels and electric vehicles really go well together

You can’t have your own oil drilling rig and oil refinery in your backyard to power an internal combustion engine vehicle, but you can have solar panels and make your own “fuel” for your EV. That’s pretty cool, and for many people that’s reason enough to go solar.

Saving money is the other big reason to do it. If you have a good unshaded roof, favorable net metering from your utility, and are able to take full advantage of the federal tax credit, you’re probably looking at somewhere in the range of an eight year financial payback period for solar panels. That means after that, your electricity is basically free for the anticipated 25 year lifespan of your system.

Most people would jump at the opportunity to have free gasoline for a decade or more, so going solar if you have an EV makes a ton of sense.