Home Icon

Loading, Please Wait...

EPRI Analysis Finds Tesla Drivers’ Charging and Driving Practices Help Inform Grid Planning for Large-Scale EV Adoption

971 Days ago

PALO ALTO, Calif., May 23, 2019 (GLOBE NEWSWIRE) -- The Electric Power Research Institute (EPRI) completed an analysis of charging and driving data collected from Tesla drivers that may help grid operators prepare for widespread electric vehicle (EV) adoption. EPRI collaborated with Salt River Project (SRP) in Arizona to collect data from nine Tesla owners for one year, to better understand the grid impact of Tesla owners’ charging behavior and driving practices.

“Knowing where, when, and how quickly EV drivers charge enables utilities to support EV owners and traditional utilities customers while planning for future electric demand and evolving load shapes,” said EPRI Technical Leader Jamie F. Dunckley, a principal investigator for this project. “Understanding EV adoption’s impact on load shape and how drivers respond to different rates for charging provides energy companies with actionable data to inform grid investment and development.”

Following an 18-month study that tracked 100 EVs in SRP’s service territory, EPRI narrowed its focus to Tesla vehicles. The earlier study determined that the largest demand spikes took place when Tesla owners when charging at public SuperChargers. Because Tesla vehicles can charge at a higher power level than other EVs today, this study’s data represents the current upper range of potential grid impacts related to EV charging.

Vehicle-mounted devices collected data as vehicles were charged and driven, regardless of where they were charged. This provided a better estimate relative to meter monitoring for projecting future load resulting from EV charging.

The devices collected data on voltage, current, GPS location, and state of charge. Summary data included total yearly kilowatt-hours (kWh) and whether charging occurred at home, at work, or in a public charging station. Other data included average kWh per charge, miles driven per kWh and grid-related data. Researchers have characterized the demand created by EV charging using “load curves” for weekends and weekdays as well as those associated with different rate structures.

“This collaboration with EPRI has provided the critical information we need to focus on planning for the large increase in the number of electric vehicles set to arrive in the near future,” said SRP Principal Environmental Scientist Kathy Knoop. “It is crucial for SRP to understand how longer-range electric vehicles will impact our grid.”


  • The participating Tesla owners used 2,380–7,159 kWh per year. The previous report which, included more EV brands, found that participants use approximately 2,700–3,300 kWh per year.
  • The Tesla participants completed 63 percent of their charging at home which is much lower than EPRI’s previous analysis on vehicles other than Teslas that found a 75 to 80 percent of EV charging took place at residential charging locations. This could be due to Tesla’s free charging at its geographically dispersed network of SuperChargers for vehicles purchased before 2018.
  • Public charging represented about 20 percent of the charging, with nearly 80 percent of that taking place at DC Fast charging stations.
  • Nearly all home charging was at Level 2 (240 volts, 16 to 40 amps).
  • More than half of the study’s vehicle owners were enrolled in a time-of-use rate, which was effective in shifting charging to night and early morning hours. 

Next Steps:

EPRI is developing a larger study to track 40 Tesla vehicles (Models S, X or 3) over 60-days using the publicly available Tesla application programming interface (API). This eliminates the need for added hardware, lowering the cost of tracking the vehicles.

EPRI expects to launch in the fourth quarter a significantly larger study, tracking thousands of vehicles. It will help EPRI refine its understanding of where EV customers charge, how much they charge, and how that varies over time and season. EPRI will focus also on how Tesla vehicles’ larger batteries and longer driving ranges combine with higher power charging to affect customer behavior and effects on the grid – looking for useful insights as EV range and charging capacity continue to increase.  

For more information about this study, please click here.

About EPRI

The Electric Power Research Institute, Inc. (EPRI, www.epri.com) conducts research and development relating to the generation, delivery and use of electricity for the benefit of the public. An independent, nonprofit organization, EPRI brings together its scientists and engineers as well as experts from academia and industry to help address challenges in electricity, including reliability, efficiency, affordability, health, safety and the environment. EPRI members represent 90% of the electricity generated and delivered in the United States with international participation extending to 40 countries. EPRI’s principal offices and laboratories are located in Palo Alto, Calif.; Charlotte, N.C.; Knoxville, Tenn.; and Lenox, Mass.

About SRP

SRP is a community-based, not-for-profit public power utility and the largest provider of electricity in the greater Phoenix metropolitan area, serving more than 1 million customers. SRP is also the metropolitan area’s largest supplier of water, delivering about 800,000 acre-feet annually to municipal, urban and agricultural water users.

Donald Cutler
Electric Power Research Institute

We Are Diffrent
Is your business listed correctly on America’s largest city directory network of 1,000 portals? Find your City Portal