The Importance of Real World Data for Utility Risk Management on Electric Vehicles

by Brewster McCracken, President and CEO, Pecan Street Research Institute

A consumer device that draws over 3,000 Watts for several hours a day doesn’t come along often.  Before 2011, there were just six such devices: AC compressors, pool pumps, electric versions of clothes dryers, ovens, space heaters and water heaters.  To put these devices in context, large homes with gas appliances in areas with temperate climates can go months without drawing more than 2,000 Watts for the entire home (Figure 1).  That’s why utility planners reasonably want to understand the possible impacts of new >3,000 Watt devices — before they become a problem.


That brings us to the newest member in the club for over-3,000-Watt-consumer devices: the electric vehicle (EV).

Will millions of customers buy electric cars over the next decade?  Will EV’s instead join smokeless cigarettes, Olestra potato chips and interactive TV in the hall of fame for product category flops?  Does the truth lie somewhere in between?

Predicting the future is tricky business.  That’s why most of us have insurance.  It’s why many companies employ risk managers.  For individual electric utilities, however, the most immediate risk isn’t a million EV’s nationwide.  It’s clustering.  Imagine, for example, a utility has 800,000 residential customers and 800 of those customers (0.1 percent) buy electric cars over three years. What happens if 500 of those customers are concentrated in four neighborhoods?

In June 2013, four university researchers from Vermont and Penn State noted that “it is likely that PEV sales will be concentrated in particular areas.  This clustering means that PEV charging loads will impact local distribution infrastructure well before the impacts on transmission or generation infrastructure is significant” [1].  In a paper presented at the 2009 IEEE Power and Energy Society General Meeting, four Electric Reliability Power Institute (EPRI) researchers agreed: “PEV loads are likely to be clustered in certain areas, increasing the potential for negative distribution system impacts” [2].

In short, a utility might experience impacts to parts of its distribution system even if just a few hundred of its customers a year buy an EV.  Or it might not.  Much depends on when these EV drivers are charging their cars, how much and at what rate.  And even as electric vehicles sales continue to increase, there isn’t much real world data on when residential customers are charging their vehicles or on the impact that clusters of EV’s have on utility transformers [3].

My organization, the Pecan Street Research Institute, is filling in this data gap through its electric vehicle research trial.  With 73 participating EV owners (a mix of Chevy Volts and Nissan Leafs), including 50 within a one-third square mile area in Austin, this appears to be the nation’s highest residential concentration of electric vehicles [4].

In each participant’s home, we installed a Level-2 charger and a home energy measurement system that reports to our research database one minute interval electricity use from the charger, the whole home and up to 23 additional circuits (Figure 2).  In the neighborhood with the highest EV concentration, we have instrumented four 50 kVA transformers to report five-minute-interval power and temperature data.  Two of the 8-home transformers have nearly 40 percent EV adoption; the other two each have one EV.  We have completed an intensive diffusion of innovation-focused research survey.  In May 2013, we began making our original data available to university researchers, utilities and other companies.

The purpose of our research isn’t to advance a particular viewpoint.  We are a research organization, not an advocacy group.  Rather, this field research is providing university researchers and utilities with unprecedented real world research data from actual EV’s, customers and transformers.  In coming issues, I will provide early insights developed from this ongoing research.  Some of what we have learned has been unexpected.  All of it (to us, at least) has been fascinating.

[1] A. D. Hilshey, P. D. H. Hines, P. Rezaei, and J. R. Dowds, “Estimating the impact of electric vehicle smart charging on distribution transformer aging,” IEEE Transaction on Smart Grid, vol. 4, no. 2, pp. 905-913, June 2013.
[2] J. Taylor, A. Maitra, M. Alexander, D. Brooks, and M. Duvall, “Evaluation of the impact of plug-in electric vehicle loading on distribution system operations,” in Proc. IEEE Power & Energy Society General Meeting, Calgary, AL, July 2009, pp. 1-6.
[3] P. Bigelow, Electric Car Sales Have Doubled, Thanks to High Gas Prices, Jul. 2013. [Online]. Available:
[4] D. Mead, Top Five Electric Vehicle Initiatives of the Year, Dec. 2011. [Online]. Available:


Brewster McCracken is President and CEO of the Pecan Street Research Institute and Pike Powers Laboratory and Center for Commercialization.

Headquartered at The University of Texas, the institute’s research focuses on electric and gas reliability and environmental and behavioral economics aspects of energy use. Mr. McCracken was one of three global smart grid project leaders invited by the government of Japan to present at the one-year anniversary conference for the reconstruction of Fukushima in March 2012. He is lead author of the institute’s research analysis comparing customer electricity use in green-built and non-green older homes, Data-driven Insights from the Nation’s Deepest Ever Research on Customer Energy Use, and he is the lead author of the institute’s forthcoming whitepaper characterizing diffusion of innovation categorization of electric vehicle owners participating in Pecan Street’s electric vehicle research (which includes the nation’s highest concentration of electric vehicles).

He was elected to two terms on the Austin City Council, serving in a city-wide at large position. Through his elected position, he founded and chaired the city council’s Emerging Technologies Committee, led the city’s collaboration with The University of Texas to establish technology incubators in bioscience and wireless technologies and served for six years as a board member of Austin Energy, the nation’s fourth largest municipally-owned utility.


Prior to holding elected office, he practiced commercial litigation for nearly a decade with two large international law firms. He is an honors graduate of Princeton University and The University of Texas School of Law, and he also holds a Masters in Public Affairs from UT’s Lyndon B. Johnson School of Public Affairs.

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