Is It Better to Charge My EV at Home or at a Public Charger?

Both options have their pros and cons

An EV home charging set up vs a public charging EV station photo illustration.

You need both home and public charging to live comfortably with an EV. If you don't have a home charger, you'll could be relying on a potentially spotty and sporadic public network. Conversely, if you don't have access to public chargers, you won't be straying too far from home. Ideally, you need both. However, you don't need to use them equally. Here's why.

The Charging Station Situation

There are between roughly 110,000 and 150,000 public gas stations compared to just under 30,000 electric charging stations in the U.S.—and many of these stations aren't stations in the typical sense.

They're packed in shopping malls, hidden in garages, in a few random spots at a hotel, and other areas that aren't as visible or easily accessible as a gas station. While handy at times, they could already be in use, too, by other drivers. (Ed. note: More stations are being added daily to the U.S. infrastructure, including broader access to Tesla SuperCharger stations.)

It is not worth your time or money to recharge at a public station when you are at more than 50 percent capacity.

The Costs of Charging

Currently, the average residential cost for electricity is under 14 cents per kilowatt-hour. To fully refuel a car with a 90-kWh battery—among the largest batteries available today—would add less than 13 dollars to a monthly electric bill. Thirteen dollars to travel 200 to 300 miles is very cheap, especially for comparable luxury cars that would triple or quadruple this cost.

Cheap, fuel-efficient cars are nothing new. The best hybrids and diesel cars—yes, there's still some market for diesel—can top 40 or even 50 miles per gallon, essentially wiping out any cost advantage to go electric. In the used car market, these vehicles are everywhere—and no EV will likely travel as far or cost as little to run as a car like a Toyota Prius.

However, electric rates do not fluctuate like oil prices, nor do they have any excise taxes for use as a road fuel. However, rates do vary across the country and on the usage of your home. In Connecticut, the average price is nearly 21 cents per kilowatt-hour, compared to 10 cents in Idaho. For example, in certain areas, electric well pumps can multiply a home's residential rate.

You have to review your personal rate, compare it to long-term gas prices in your area, and decide. Usually, you'll come out ahead by charging an EV at home.

Consequently, if you only use public chargers, you may be charged just as much, if not more, than you might for gas. It’s because the best public stations, known as fast-charging or Level 3, use three-phase commercial service that's many times higher than what you can legally wire to your home.

Cars using this high-voltage, high-amperage service pay a premium. Often, charging stations will either charge a flat rate or charge you by the kilowatt-hour at a rate that's double or triple what you would pay at home.

Even charging at Level 2 stations—the same type as you would have in your home—one hour can cost between $10 and $15 for just 100 miles of range, depending on the car and charging station.

The Speed Equation

The greater the power, the quicker your car can charge. Fast-charging Level 3 stations can output between 50 to 350 kW of power—that's six to 44 times greater than the fastest home chargers. The exact output varies by station and the amount your car can handle.

Many EV automakers estimate how long it takes to charge from zero to 80 percent battery on a fast-charging station. It’s not a standard metric, but it is a rough comparison depending on the EV's battery capacity and charging limitations. On a Level 3 connection, some EVs may only need 30 minutes, while others may require an hour. On a Level 2 connection, it could be four to eight hours.

However, automakers choose 80 percent as the endpoint because charging from 80 to 100 percent takes just about as long as zero to 80 percent. All charging stations reduce the power as a battery fills up to avoid destroying the battery with excessive heat. As a result, it is not worth your time or money to recharge at a public station when you are at more than 50 percent capacity.  

Home chargers are meant to charge an EV overnight. Once you're done using the car for the day, letting it charge for 10-plus hours is not a concern. You'll save money, and you'll wake up to a fully charged vehicle.

Battery Longevity Factors

Unfortunately, fast charging isn't a free lunch. The faster a battery charges, the quicker it will age. Fast charging places significant stress on the battery's cells. It's why Tesla and most automakers do not recommend fast-charging their EVs on a daily or even weekly basis; there is no scientific formula for these recommendations.

But in general, fast charging generates lots of heat that the car cannot fully dissipate. Batteries have a finite number of charge cycles, and fast charging accelerates this timeline. If you want to preserve your EV for the long-term, you need to charge primarily at lower voltages and avoid high-voltage charging stations regularly.

Charging too quickly or charging when it's unnecessary for your next day's trip will cause the battery to reduce capacity at a faster rate. Fully discharging a battery will also put more wear and tear on the cells. Batteries are complex and very sensitive compared to gasoline tanks. If you plan to keep your EV for more than three years, these are essential considerations.

Convenience Matters

Your home charger is always at home, in the same spot, just for you. That's convenience you can't beat. Public chargers, on the other hand, have no consistency.

They could be at a highway rest stop, as Tesla does in many parts of the Northeast, but often, they're tucked away in obscure, unmarked locations that require knowledge and planning. Some public chargers are broken or out of service; there are never attendants at these stations to repair them or offer advice. Many stations require pre-existing accounts and will not let you "pay at the pump."

After all this, you won't be able to use all of the stations that show up on your navigation or phone app. There are four competing plug standards, most of which are incompatible with each other.

Of these, stations may output power at varying rates—so the same station you visit in Massachusetts may recharge at a slower rate than in New York. It is a messy and altogether frustrating experience to rely on public chargers.

For these reasons alone, you must have a home charger. Rely on public charging when you must but keep home charging at the top of your list.

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