Charging your electric car at home

By Hannah McKenzie
Charging your electric car at home

There are three options for charging a plug-in electric vehicle — two for home charging and another for charging stations seen at rest stops or and car dealerships.

Q: I'm curious about electric vehicles. What do I need to charge a car at my house, and how much would it cost?

A: If you have a house guest with a plug-in electric vehicle (PEV), there's no trouble because a standard 120-volt household outlet is all you need. It will be slow but works great if Uncle Max is spending the night.

Owning a PEV is a slightly different ballgame from an electricity perspective. In terms of electricity use, charging a vehicle at your home every night is like adding a member to your household.

Charging options

"Level 1" is a fancy term for a 120-volt household outlet. This is the simplest charging method because no special equipment is required. The downside is waiting eight to 10 hours for a full charge.

"Level 2" requires special charging equipment about the size of a large lunchbox. The charger can be hardwired to your home's 240-volt electrical system, which is the same voltage as a clothes dryer. A full charge can be completed in two to three hours. Prior to installation, your electrical wiring should be inspected for safety and integrity. In some situations, a service panel upgrade may also be required. Installation of these chargers costs from $300 to $3,500 depending on equipment and labor. These are the most common charging stations, also found at offices, shopping centers and restaurants.

The third option is "fast chargers" that are more expensive and typically found at rest stops, fueling stations and car dealerships instead of at homes. These chargers take about 20 minutes for an 80 percent battery charge.

Contact your electric cooperative and electrician

Ask the following questions:

  1. Is there an off-peak rate structure that can save money?
  2. If you're installing a Level 2 charger or "fast charger," ask about the size of your home's electrical service and panel? Call your co-op to determine if a transformer upgrade is needed. Also, your electrical contractor may determine that your home's service panel needs to be upgraded to accommodate the new charging load.

Charger location

There are three things to consider when selecting a charger location:

  1. Available space for the outlet and/or charger.
  2. Charging port location on the expected vehicle.
  3. Whether the driver typically backs into the parking spot or pulls in front first.

Eliminate locations that would require a cord to be wrapped around or draped over the vehicle to reach the charging port. Look out for garage doors! The charger needs to be as close as possible to the PEV's charging port so the cord is not easily damaged or becomes a tripping hazard.

"Topping off" your vehicle's battery while you're driving away from home is easy with mobile apps that show publicly-available charging stations. There's also a website sponsored by the U.S. Department of Energy that can help you find charging stations near an address or zip code: check out www.afdc.energy.gov

Electricity costs

Charging a battery is cheaper than fueling a gasoline car. If you were to drive the U.S. average of 40 miles or less per day (nearly 15,000 miles per year) at an average electricity cost of 12 cents per kilowatt-hour, your typical daily charging cost would be $1.38 or approximately $40.80 per month.

Comparing that to a gasoline car with 30 miles per gallon paying $3.50 per gallon of gas, the typical daily fuel cost would be $4.65, or approximately $140 per month. Also, all new PEVs offer a timer that allows you to set the charge time for off-peak hours.

PEVs use a small enough amount of energy that I wouldn't ask an overnight guest for reimbursement. After all, you wouldn't charge them for the hot water they used to bathe.

About the Author

Hannah McKenzie is a residential building science consultant at Advanced Energy in Raleigh who specializes in working with nonprofit developers like Habitat for Humanity to make new affordable housing energy efficient.

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