It’s the end of the year and I find myself reflecting back on my electric-vehicle (EV) research efforts in 2015: I’ve written three full-length reports and four (now five) blogs; attended the EV Roadmap Conference in Portland, Oregon, in late July; and presented at the 2015 E Source Forum in October. My work has spanned topics such as incentive programs, demand-response technologies, and, most recently, charging infrastructures.

In my research, I found that EV drivers generally don’t use public infrastructure to charge their cars nearly as much as they use residential or workplace infrastructure. Based on data from the EV Project, Figure 1 depicts the percentage of total energy consumed by an average EV at various charging locations:

FIGURE 1: Most charging occurs at home and at work

According to researchers from the Idaho National Laboratory’s EV Project, most Nissan Leaf and Chevrolet Volt owners charge their vehicles predominantly at home. Drivers seldom use public stations, and they opt to charge fairly often at workplace stations if they have access to them.
Figure showing energy consumption of select EVs according to charging location

While attending the EV Roadmap Conference, I thought about this data when attendees were all charged up over installing public stations. Specifically, I heard one utility representative speak about the widespread public charging infrastructure in his service territory—a city named by the presenter to be “the best place to own an EV” because of its 1:1 EV-driver-to-public-charger ratio. The audience was audibly impressed with this utility’s EV supply equipment (EVSE) efforts, but I felt confused. After all, I had just spent the previous week picking through and analyzing different charging-behavior study results, and from what I could tell, public charging stations were underutilized. Why bother installing expensive public EVSE when 64 to 86 percent of charging occurs in customers’ residential garages?

The opposing argument goes something like this: Drivers need public EVSE to increase driving radius and reduce their range anxiety. Which is true. If the average EV driver doesn’t want to be limited to a 40-mile radius around their home, they will need to rely on public infrastructure to get the extra miles. My next question though is Who’s opting to interrupt their 40-plus-mile journey with a one- to seven-hour wait at whatever Level 2 public charger is locally available? (Of course, direct current [DC] fast chargers will get the job done more quickly, but those are harder to come by.)

In October, the Idaho National Laboratory (INL) published its latest research on charging behaviors and began to address the question of who’s charging at public stations. Its Leading the Charge (PDF) infographic features highlights from the full-length report and claims that “charging infrastructure should be focused at home, workplaces, and in public ‘hot spots’ where demand for Level 2 or DC fast charging stations is high.” The complete report (Plug-in Electric Vehicle and Infrastructure Analysis [PDF]) goes on to suggest that demand is highest for public charging at workplaces and retail facilities.

I’m still not daydreaming about the mass expansion of public EVSE, but I appreciate INL’s efforts to pinpoint optimal placement. Let’s just hope that in “the best city to own an EV,” the chargers are outside the local shopping mall—and that the EV Roadmap Conference attendees who oohed and aahed during that session I attended will place their future chargers wisely.


Thank you, Logan. I appreciate you year-in-review reflection.

@Patrickagnew, thanks for reading!

Contributing Authors

Editor, Editorial

In January 2019, Logan Jacobson began working as a content manager with E Source. Previously, she researched energy-efficient technologies...